Dictionary of Ichthyology

The Wayback Machine - https://web.archive.org/web/20091206035232/http://www.briancoad.com:80/Dictionary/M.htm

Revised: 03 October 2009

M = instantaneous rate of natural mortality (when natural and fishing mortality operate concurrently it is equal to the instantaneous total mortality rate, multiplied by the ratio of natural deaths to all deaths (Ricker, 1975). Also called force of natural mortality).

m = 1) annual mortality rate (the ratio between the number of fish which die during a year from causes other than fishing and the number alive at the beginning of that year. Also called annual natural mortality rate, conditional natural mortality rate, seasonal natural mortality rate). Also abbreviated as n.

m = 2) conditional fishing mortality rate (the fraction of an initial stock which would be caught during the year (or season) if no other causes of mortality operated (Ricker, 1975). Also called annual or seasonal fishing mortality rate).

m. = abbreviation for mihi, meaning belonging to me, of me (as of authorship of a new species, or used to show the writer's responsibility for a statement or proposal).

M74 syndrome = mortalities in Baltic Sea Atlantic salmon stocks appearing first in 1974. Mortalities occur just prior to end of yolk absorption and caused by pollution or vitamin-deficiency.

maceration = the softening of tissue in various solutions prior to its removal from bones, a technique in osteology.

Mackenzie River dory = a river fishing boat with a flat bottom, rigid hull and upswept prow about 14-18 feet long. Also called drift boat.

mackerel = 1) Scomber scombrus, derived from the French maquereau, a word also used for pimp and, anecdotally, for the fish which leads female shads to their mates in spring.

mackerel = 2) the ban on cigarettes in U.S. prisons led to the use of small packets of shrink-wrapped mackerel as currency. Each packet is worth a dollar and reputedly tastes awful.

mackerel box = a mackerel nursery area around the south-west peninsula of England and part of the Celtic Sea within which directed fishing for mackerel by purse seiners and pelagic trawlers is prohibited.

mackerel breeze = a breeze that ruffles the water and favours the catching of mackerel.

mackerel gale = a strong breeze that ruffles the water and favours the catching of mackerel (obsolete).

mackerel plough = a knife used to crease the sides of poor-quality mackerel in order to improve their appearance.

mackerel sky = a type of altocumulus clouds, indicating moisture and instability; hence the saying "Mackerel sky, mackerel sky, Never long wet and never long dry". Presumably named for the wavy pattern as seen on mackerel flanks.

mackerel snapper = derisory or semi-humorous comment on Catholics who eat fish on Fridays (U.S.A.).

mackerel style split fish = fish that have been split along the back, leaving the backbone in place. Can then be laid flat in barrels.

mackerel tabby cat = a cat with characteristic, gently wavy bars on the flank, reminiscent of the fish pattern. The most common tabby pattern. Also called fishbone tabby.

macrocentric scale = replacement scale (a scale which has formed in the place of a lost scale. The centre portion of a replacement scale is equal in size to the one lost but lacks ridges and radii. Not useable for aging purposes. Also called regenerated or latinucleate scale.

macrohabitat = rivers or lakes in fresh waters, cf. mesohabitat and microhabitat.

macroincrement = growth increments more than 50 μm in otoliths or other structures used in ageing, observable with a binocular microscope and used to describe seasonal increments.

macromelanophore = a normal-sized melanophore or brown-black pigment cell, relatively large compared to a micromelanophore (q.v.).

macrophthalmia = 1) swollen or enlarged condition of the eyes, sometimes attributable to parasites or physiological irregularities.

macrophthalmia = 2) that stage of development in Anguilla where the eyes enlarge, the body becomes silvery, usually in preparation for migration.

macrosmatic = forms with well-developed olfactory sense, e.g. most Elasmobranchii, Anguilliformes. Opposite of microsmatic, q.v.

macula neglecta = a sensory structure located in Teleostomi in the utriculus of the inner ear near the opening of the ampulla of the posterior vertical semicircular canal, in selachians within a duct (posterior canal duct) through which the posterior vertical semicircular canal connects with the sacculus, while in the batoids it lies in the wall of the sacculus adjacent to the opening of the duct. It may have a neuromast associated with its sensory tissue. This structure has been demonstrated to be a sensitive vibration receptor in Raja. Also called crista neglecta, crista quarta, or papilla neglecta.

macula bucca = a photophore above the hind end of the upper jaw in Myctophidae. Abbreviated as Bu.

macula cervicis = a photophore at the upper end of the gill cover where it meets the lateral line in Myctophidae. Abbreviated as Ce.

macula suprapectoralis = a photophore above the base of the pectoral fin in Myctophidae. Abreviated as PLO.

macula supraorbitalis = the photophore on the posterodorsal border of the orbit in Myctophidae. Abbreviated as Suo.

macula supraventralis = a photophore above the ventral fin in Myctopbidae. Abbreviated as VLO.

maculae anales anteriores = a row of photophores along the base of the anal fin and lower side of the caudal peduncle (not including the Prc's at the base of the caudal fin) in Myctophidae, the AOa row is mostly above the anal fin base.

maculae anales posteriores = a row of photophores along the base of the anal fin and lower side of the caudal peduncle (not including the Prc's at the base of the caudal fin) in Myctophidae, the AOp is mostly on the caudal peduncle.

maculae branchiostegae = photophores along the lower jaw of Myctophidae. Abbreviated as BR.

maculae operculares = photophores on the gill cover, one near the anterior base of the preopercle, one in front of the anterior part of the subopercle, and one antero-dorsally to the operculum. Abbreviated as OP.

maculae posterolaterales = ventrolateral photophore(s) above the AO series which lie along the base of the anal fin but below the lateral line in Myctophidae. Abbreviated as Pol.

maculae praecaudales = photophore(s)on the lower half of the caudal peduncle at the base of the caudal fin in Myctophidae. Abbreviated as Prc.

maculae pectorales = a row of photophores on the breast in front of the pelvic fin in Myctophidae. Abbreviated as PO.

maculae subpectorales = photophores below the pectoral fin and above the PO row in Myctophidae. Abbreviated as PVO.

maculae supraanales = a sloping, ventro-lateral row of photophores above the anal fin origin in Myctophidae. Abbreviated as SAO.

maculae ventrales = a row of photophores on the abdomen behind the ventral fin in Myctophidae. Abbreviated as VO.

mad = 1) plentiful, gathering in large numbers, in reference to fish (Newfoundland).

mad = 2) a square net fixed by four stakes in a river for catching salmon or trout (Clydesdale dialect, Britain). Also called maud.

Madeira = a grade of cod which was light-salted, well-dried, and hard, and eighteen inches long, sold to sack or Madeira ships or to Brazil (the term referred to the quality, not the destination) (Newfoundland).

maggot = the larva of an insect (bluebottle) used as bait in European angling, e.g. for such cyprinid species as Abramis brama, Cyprinus carpio, Rutilus rutilus. They may be coloured with food dyes (e.g. pinkies) or flavoured. Also called gentles or gents. Maggots become a caster when in a chrysalis form.

magnet = fish magnet (a moveable electrode used to bring up a school of fish that normally is too deep for a purse seine to catch).

mahi muratib = the Order of the Fish ("fish dignity" in Persian and Arabic), an honorary badge or dignity, shaped like a fish (supposedly Labeo rohita in Moghul India). Said to signify youth, bravery, perseverance and strength. Reputedly founded by Khusru Parviz, King of Persia (A.D. 591-628), and thence passed to the Moghul Emperors of Delhi and to the Court of Oudh.

mahogany = two parts gin and one part treacle, beaten together; a drink of Cornish fishermen.

maiden = 1) a fish (salmonid), whether male or female, which has not spawned, and is maturing to spawn. Also called a virgin.

Maillard reaction = browning (discolouration of fish, especially of dried or canned products, caused by a deteriorative reaction between amino groups of proteins and carbonyl groups of sugars during storage. There are also flavour changes and loss of some nutritive value. Known also as the non-enzymatic browning reaction).

main fish = the most important fish species in any given situation, e.g. in a catch, a waterbody, a study, etc.

main line = the principal line in a longline from which branch lines depend with hooks attached.

main stream = the principal current of a flowing course of water, a river, stream, etc.

maingayic acid = a plant piscicide from Callicarpa maingayi (Verbenaceae). Other piscicidal plant chemicals include callicarpone, huratoxin, ichthyothereol, inophyllolide, juglone, justicidin, rotenone, and vibsanine, all q.v.

mainstream = the largest or dominating stream of a given area or drainage system.

mainstream flow = that part of the flow in a river, for example, that is away from the bottom and surface and is not under the influence of the boundary layer.

maintainable yield = the largest catch that can be maintained from the population, at whatever level of stock size, over an indefinite period. It is identical to the sustainable yield for populations below the level giving the maximum sustainable yield and equal to the maximum sustainable yield for populations at or above this level.

maintenance = the continued use of, or support for, a correct name in nomenclature.

maintenance ration = the amount of food required for life without increase in weight.

maize = 2) sweet corn used as a bait for such fish as carp. When bought dried needs to be soaked or boiled to make it softer. Can be fermented and various flavours added.

major carp = a larger member of the family Cyprinidae, usually referring to those species used in aquaculture. See Chinese major carps and Indian major carps.

major rays = the fin rays counted in describing and identifying a fish. Includes branched rays and one unbranched ray, omits anterior rudiments. See, e.g., dorsal fin ray count for details. Also called principal rays.

makassar = anchovies headed, salted for several days, then mixed with rice, yeast and spices forming a red pickle, and then packed in bottles.

make bawn = to prepare a beach for drying salted cod by making a flat expanse of rocks (Newfoundland).

make fish of one and flesh of another = to show partiality, to make an invidious distinction.

make fish of one and fowl of another = to show partiality, to make an invidious distinction.

make the fish = to dry salt fish by alternate exposure to sun and piling in stacks or faggots to allow moisture inside to diffuse to the surface.

making fish = preserving fish by salting and drying as in the cod fisheries of Newfoundland.

malachite green = a dye and fungicide once used in fish farms but now banned as being suspected of causing cancer.

malar = 1) pertaining to the cheek or sides of the head, e.g. malar spines or thorns found in some male Rajidae close to the edge of the disk opposite the eye.

malar = 2) supramaxilla (the dermal bone(s) on the upper side of the posterior end of the maxilla. Salmonidae have one supramaxilla while Sternoptychidae have two. Lost in more advanced Teleostei. Also called supramaxillary, surmaxilla, surmaxillary and jugal).

malassol = lightly-salted caviar (malassol is Russian for little salt) but now also used for any high-quality caviar. Salt content should be less than 3%. Russia and some eastern countries (but not Iran or the U.S.A.) allows addition of borax that sweetens the caviar and helps preserve it.

Malawi bloat = a condition similar to dropsy (q.v.) seen in cichlids from the East African rift lakes (originally those from Lake Malawi). Progress is more rapid than in dropsy. Fish show lethargy, appetite loss, increase respiration, gasping at the surface, abdominal swelling, with death in less than 3 days. Causes are uncertain but include bacterial infection and poor diet.

male-with-harem family = patriarch/matriarch family (the condition in Cichlidae where the male defends a large territory, which includes multiple spawning sites of several females. Each female assumes the responsibility of her own brood. The male is polygamous, and clear sexual dimorphism is present. This form takes place among cavity brooders).

malleus Weberi = tripus (the fourth of the four Weberian ossicles, q.v., so-named for its three processes. The anterior process joins it to the intercalarium by a ligament, the median process joins it to the third vertebral centrum and the third, posterior process contacts the anterior wall of the gas bladder through a transformator process).

malpigmentation = a major deviation from the normal colouration of the body or part of the body.

mam-ruot = fermented fish paste made from muscle tissue and intestines (Vietnam).

man = 1) a pile of rocks or pinnacle lined up with another land feature in order to locate a fishing ground (Newfoundland). See also mark.

management = in fisheries this term applies to regulations such as catch quotas and closed seasons.

management authority = the legal entity which has been assigned by a State or States with a mandate to perform certain specified management functions in relation to a fishery, or an area, e.g. a coastal zone. Generally used to refer to a state authority, the term may also refer to an international management organisation.

management objective = a formally established, more or less quantitative target that is actively sought and provides a direction for management action, e.g. a percentage reduction in fleet capacity, a competitive income for fishers.

management organisation = an institution or arrangement established (usually between two or more States) to be responsible for activities related to fisheries management, including consultation between parties to the agreement or arrangement, formulation of the fishery regulations and their implementation, allocation of resources, collection of information, stock assessment, as well as monitoring, control and surveillance.

management procedure = a description of the data to collect, the way to analyse it, and the way to translate the analysis into actions.

management reference points = conventional (agreed values) of indicators of the desirable or undesirable state of a fishery resource of the fishery itself. Reference points could be biological, e.g. expressed in spawning biomass or fishing mortality levels, technical (fishing effort or capacity levels) or economic (employment or revenues levels). They are usually calculated from models in which they may represent critical values.

management strategy = narrowly defined as the combination of a particular data collection system, a particular stock assessment technique and a particular harvest control rule and its implementation. Alternative management strategies can be compared against each other via simulation.

management unit = a stock; an independent set of populations recognised for the purpose of management of an endangered species or an exploited species.

mandatory change = a change in spelling of a name required by the International Code of Zoological Nomenclature.

mandible = the lower jaw, used in the sense of a functional unit without respect to the bones and cartilage making up the jaw.

mandible length = lower jaw length (measured from the anterior tip of the lower jaw to the posterior angle).

mandibular arch = the cartilages and bones of the visceral skeleton forming the jaws. The upper jaw elements are the palatoquadrate or pterygoquadrate cartilages, the lower jaw ones Meckel's cartilages and the angular. This is the basic jaw, the primary mandibles, which have several ossification centres in bony fishes. Teeth and dermal bones are later evolutionary additions and are called the secondary mandibles.

mandibular canal = the portion of the preoperculo-mandibular canal (of the cephalic sensory canals) running along the lower jaw.

mandibular labial teeth = teeth found just below the infraoral cusp or lamina and just above the lower margin of the disk in lampreys (Petromyzontidae).

mandibular pore = one of a series of pores of the head lateral line system found on the under surface of each jaw. Part of the preoperculo-mandibular canal.

mandibular symphysis = the joint between the left and right mandibles at the jaw tip.

mandibular valve = the buccal flap attached to the inside of the lower jaw which helps keep water from flowing out of the mouth during respiration.

mang ō roa (long shark) = ika-roa (the long fish in Maori legend that gave birth to all the stars in the Milky Way. Also called mangōroa i ata (long shark in the early dawn)).

mangōroa i ata (long shark in the early dawn) = ika-roa (the long fish in Maori legend that gave birth to all the stars in the Milky Way. Also called mang ō roa (long shark)).

manta tow = 1) towing a snorkeller behind a boat at a constant speed, the snorkeller holding onto a manta board. The board has hand grips and facilities for recording data. The tows are usually of short duration (e.g. two minutes) allowing the snorkeller to remember observations that are then written down on a sheet attached to the manta board when the boat stops. Usually used to assess reef habitat but can be used to record fishes.

manure = of fish, dried and powdered used as fertiliser in fish ponds to enhance productivity.

manuring = fertilisation (2) in aquaculture, the improvement of water productivity by addition of natural or artificial compounds).

manuscript = a text, either handwritten or typed, but not available in multiple copies. Used for the copy of a scientific paper submitted to a journal for publication. Abbreviated as MS or MSS (plural).

manuscript name = an unpublished scientific name; may be intended for eventual publication or be used in correspondence or in public speech. Has no standing in nomenclature until acceptably published.

marginal blastomere = a cell incompletely cleaved before the yolk syncytial layer forms located in the surface layer just at the rim of the blastodisc.

marginal cost of effort = the incremental cost incurred by applying one additional unit of fishing effort.

marginal habitat = a habitat supporting only a few species or individuals because of the limiting environmental conditions.

marginal increment = the region at the edge of a structure used in age determination, a fraction of the last complete annual or daily increment.

marginal membrane = the border of the buccal funnel just inside the oral fimbriae and just outside the toothed area in lampreys (Petromyzontidae).

marginal yield = the increase in yield obtained by an increase in fishing effort by one unit.

marginalia = information recorded in the margin of a document. Also called marginal notes.

marginals = the circle of teeth around the perimeter of the buccal funnel of a lamprey (Petromyzontiformes).

marginaria= ligaments that attach otoliths to the chamber wall and transmit movements to the brain, helping to maintain equilibrium.

mariculture = marine cultivation or aquaculture of organisms in tanks, pens, ponds or cages or net enclosed areas in the open sea. Fish are usually raised to market size; a marine hatchery is also a mariculture facility but fish are usually released as young.

marinade = acidified brine, acetic acid, olive oil or vinegar with or without spices in barrels or special containers in which fish are soaked. The cured fish are packed in mild acidified brine variously with spices, sugar, wine, vegetables and flavourings, e.g. rollmops, Bismarck herring. Salt helps firm the flesh. Chilled marinades have a shelf life of 1-2 months, canned marinades much longer. The pH must not exceed 4.5 as below this spoilage does not occur and food poisoning bacteria do not grow. However some bacteria and enzymes are active and aid ripening, contributing to texture and flavour. Cold marinades are preserved by their acid and salt content, cooked marinades by this and by heat or pasteurisation.

marine refuge = an area protected against fishing. This may be a refuge from which commercial stocks are replenished.

marine reserve = an area of the sea set aside for the protection of organisms such as fishes and/or for their scientific study.

marine salt = a complex mix of salts used to imitate sea water for a marine aquarium. Not to be confused with aquarium salt, q.v.

marine snow = organic particles and dead organisms that sink into the deep sea where they form a basis for life without sunlight. Also called plankton rain.

marine survival rate = the portion of a migratory population that survives the open-ocean phase.

marine transgression = land flooded by the sea as land sinks or sea level rises.

marinist = a scientist who studies the sea or an expert in maintaining aquaria (rarely used and not in dictionaries as of 17 June 2006).

mark = 2) a region of similar structure or optical density laid down during growth of hard parts used in ageing. Also called band, ring and zone.

mark = 3) any sign on or in a fish enabling it to be distinguished from other fishes. Excludes tags which are artificial objects.

mark = 5) a land feature which, when lined up with another one, enabled a fisherman to position himself over a fishing ground. See also mark (1) and man.

mark-recapture study = the tagging, release and recapture of fish to estimate population size, movements, migrations, mortality and growth.

marked = fish stained, tattooed, dyed, tagged or fin clipped and then released and recaptured for studies of growth, movement, etc.

marker float = 1) large, brightly coloured floats used to mark a particular fishing area for angling. Usually cast out with an additional rod and reel apparatus, a lead weight on the end of the line, and the float running free. Once tension on the line is released the float surfaces and marks the fishing area.

marker float = 2) one of series of floats used to fix a gillnet at a certain depth.

market = of fish, any area selling fish but usually refers to a large covered establishment with diverse products.

market category = a general grouping of fish at market that is not species determined, rather a general category determined by price per weight.

market glut = too many fishes becoming available, thus straining the resources of buyers, processors and wholesalers and causing prices to drop to very low levels.

market name = a common name assigned to a fish sold for consumption to encourage sales, e.g. spiny dogfish (Squalus acanthias, a shark) became rock salmon.

market price support = measures that raise prices for fish consumers, e.g. tariffs, tariff quotas, quantitative restrictions, import licensing, etc.

market run = a voyage from the fishing grounds to the point of export, especially a rapid passage under full sail in the past (Newfoundland).

marketable size = the weight an aquaculture product must attain before being acceptable for sale, either legally or by consumer choice.

marking = an identification system involving various methods (fin clipping, colouring, biotelemetry, radioactive markers, tattooing, branding, tagging, etc.), used for individual identification and for studies on movement, growth and other biological studies. Also called tagging.

marlin tower = a low platform in a fishing boat from which spotters look for fish. A high platform is a tuna tower.

marrow spoon = a long and slender spoon used by fly fishermen to extract stomach contents of fish and thus determine what the fish are feeding on and what artificial fly would be appropriate.

marsh = a type of wetland that does not accumulate appreciable peat deposits and is dominated by herbaceous vegetation. Marshes may be either fresh water or saltwater and tidal or non-tidal.

Marshall's gland = alkaline gland (a paired organ in the genito-urinary apparatus of Raja (and probably other skates and rays) whose cavity is fluid filled).

marsipobranch = a purse-gill, consisting of a round cavity or pouch lined with gill lamellae found in Myxini and Petromyzontiformes.

marsupium = the name applied to the brood-pouch in Syngnathidae and Solenostomidae. In Syngnathidae it consists of a vascularized groove formed by flaps of skin along the underside of the tail of males (subcaudal marsupium); in Solenostomidae it is a pouch formed by the pelvic fins, provided with many long filaments, and found only in the female (ventral fin marsupium).

masago = caviar from Mallotus villosus (Osmeridae), usually small eggs, bright yellow to orange in colour.

masculinisation = direct sex reversal by doses of male hormones, e.g.17a-methyl testosterone, in the feed during the early stages of development. Used for tilapia and catfish farming where males are the desired gender. Also used in female broodstock that then produce sperm with homogametic (XX) chromosomes which then produce an all-female cohort when crossed with normal eggs.

mask = 2) to enmesh or catch fish in a net, to swim into a net and thus trap themselves (Scottish dialect).

masoten = dylox (0-0-dimethyl-2,2,2-trichloro-1-hydroxy-ethyl phosphonate, an insecticide used in control of parasitic copepods. Also called dipterex).

mass marking = making all individuals in a population of fish so that individuals can be identified later in their life history.

master float = a float attached to the distal end of of the fleet end rope used to locate the gillnet fleet end.

master of the fishery = the man in charge of a fishing crew and the operations involved in catching and processing fish (Newfoundland).

master of the seine = seine master (a man in charge of a boat and crew fishing with seines).

master sinker = a heavy weight attached to the gillnet fleet end to control drifting.

masula = a large, open boat used on the east coast of India for operating shore seines and steered by a paddle sweep.

matanza = a slaughter, used for the traditional fishery for bluefin tuna in the Mediterranean.

match fishing = competitive coarse fishing in Britian with a peg (fishing spot) selected randomly for each angler, a time limit and rules. Usually the maximum number or weight of fish caught wins the match. Since there are many more small fish than large ones, the effort may be designed to catch large numbers of small fish, often at a rate of a fish every 20 seconds using very fine lines and minute hooks.

match reel = a very light reel that has a special spool taking only the amount of line to be used (100-150 m).

match rod = strong but light fishing rods made of carbon fibre and up to 15 feet long.

matching the hatch = an angler's attempt to choose an artificial fly that resembles natural insects hatching and being fed on selectively by fish. Also called imitative flyfishing.

matelote = a French fish stew made with wine, sometimes thickened with cream and egg yolks (Alsatia) or with cider and Calvados (Normandy).

Material Safety Data Sheet = documents form the manufacturer of a chemical outlining its toxicity, volatility, flammability and other safety related information. Posted in laboratories where such chemicals are use; formalin is probably the commonest and most toxic chemical encountered by ichthyologists. Abbreviated as MSDS.

maternal histotrophe = histotrophe (ovarian or uterine milk, a secretion produced by teleost livebearers for absorptive feeding during fish ontogeny).

matje cured herring = matje herring gutted, roused, mild cured and packed in barrels filled with blood pickle at 80� brine strength.

matje herring = young fat herring with gonads slightly developed or undeveloped, i.e. caught early in the season (from the Dutch for virgin).

matriarch/patriarch family = the condition in Cichlidae where the female watches over the brood, while the male defends the territory. When the fry become free-swimming, the parents bear the tasks of parenthood equally. This family form is usually formed by monogamous, open-water brooders. Sexual dimorphism and dichromatism is common. See also patriarch/matriarch family.

matriachal family = the condition where no bond is formed between a spawning pair. The female cares and guards the eggs and the fry, e.g. in some Cichlidae. In this family pattern, the fish are agamous, and usually the female is an ovophile mouthbrooder.

matrix-rich zone = D-zone (that part of a micro-increment of an otolith that is dark in transmitted light or is a depressed region when acid-etched and seen with a scanning electron microscope. It has more organic matrix and less calcium carbonate than the L-zone, q.v. Also called discontinuous zone).

matroclinous inheritance = the hereditary mechanism resulting in only the chromatin of the mother being passed on to the offspring which are all daughters. Also spelled matriclinous.

matronym (adj. matronymic) = a scientific or common name dedicated to a female person. See also patronym.

matrotrophic viviparity = internal fertilisation of eggs with the mother providing some nutrition to developing embryos and with the young born as larvae.

Matsya = fish in Sanskrit (मत्स्य) and the first avatar of Vishnu in Hindu mythyology, usually represented as a man with his lower half in the shape of a fish.

Mattanza = a Mediterranean tuna trap with leaders over a mile long and a series of large chambers which eventually concentrate the passing school in a killing room. The walls of netting in this last room are lifted up and the tuna gaffed and hauled into boats.

Matthiessen's ratio = the proportion between the distance from the centre of the lens to the retina divided by the radius of the lens in fishes. The proportion is usually 2.55. All fish eyes, therefore, have the same proportions, regardless of size.

mature individuals = the number of individuals known, estimated or inferred to be capable of reproduction. Excludes adult fish that are incapable of reproduction because of environmental or behavioural reasons.

mature river = a river with a less steep gradient, more discharge and a slower flow than a youthful river, many tributaries and its channel erodes wider than deeper. See also youthful, old and rejuvenated rivers.

maturity = fish of a given age/size capable of reproduction; attainment of first spawning.

maturity coefficient = the weight of the gonad as a percentage of the weight of the whole body, or the gutted body weight.

Matsyendra = one of the Vishnu's incarnations as a fish, first Avatar of the Dasavatharas or Matysa in Hindu mythology.

maund = 1) 4 kg or about 9 pounds, used in the Persian Gulf for fish weights in the market.

maund = 2) a basket or hamper. Those used for herrings were made of osiers and were open-ribbed; other were used for catching salmon. A big maund held about one hundredweight. Also spelled man, mand, maun and mawn.

Mauthner's xon (neuron) = one of the two giant neurons linked to parts of the acoustico-lateralis, optic, and cerebellar systems, and to somatic motor neurons by way of decussating (intersecting) giant nerve fibres that run the length of the spinal chord. This short circuits ordinary reflex paths and provides the rapid and co-ordinated response of swimming muscles for rapid escape. Found in larvae of Petromyzontidae, in Holocephali, Teleostomi and in tadpoles and aquatic urodeles, absent in Selachii and Rajiformes.

maw = 1) the dried stomach or swim bladder of a fish used for industrial purposes.

maw = 2) the mouth, stomach, jaws, or gullet of a voracious animal, presumably including the larger fishes.

maw bladder = gas bladder (a thin membranous, sometimes alveolated sac in the dorsal portion of the abdominal cavity. Contains a varying mixture of gases, not identical to the composition of air. May be one, two or three chambered. May be connected to the gut by a tube, the ductus pneumaticus (then called physostomous) or unconnected (then called physoclistous). May function as one or more of:- hydrostatic organ, sound producing organ, sound receptor, respiratory organ. Found in Actinopterygii. Often lacking in bottom fishes. Also called swimbladder).

maxilla (plural maxillae) = the dermal bone forming part of the upper jaw, displaced inwards by the premaxilla in more modern Teleostei. It may bear teeth. Also called maxillary which is also the adjective.

maxillar cartilage = palatoquadrate (the cartilaginous, functional upper jaw of Elasmobranchii and Holocephali and the embryonic upper jaw of other gnathastome vertebrates. In adult Dipnoi, Crossopterygii and Actinopterygii, produces the autopalatine, metapterygoid and quadrate bones. Also called palatoquadrate or palatoquadratal bar, palatoquadrate cartilage, pterygoquadrate bar, epimandibular cartilage and maxillar cartilage).

maxillary extension = an expression of relative mouth size measured with the mouth closed. When the mouth is open the maxilla is displaced forwards in relation to the eye, and it is the extension of the maxilla in relation to the eye that is used to describe mouth size.

maxillary length = greatest length of that bone. Often misapplied to the length of the whole upper jaw when the upper jaw includes the premaxilla.

maxillary valve = the buccal flap attached to the inside of the upper jaw which helps keep water from flowing out of the mouth during respiration.

maxillo-infraorbital = a paired bone ossifying from the lower orbit (corresponding with the jugal) and ventrally close to the mouth edge.

maxillo-mandibular ligament = a ligament intimately involved with the adductor mandibulae muscles. It attaches to the proximal end of the maxilla, the opposite end attaches to the angular bone near the quadrato-articular joint and a third deeper part attaches to the coronoid processes of the dentary and the angular bones and then passes to the lower jaw. Adductor mandibulae (part 1) inserts at the centre of the of the ligament and part 2 and part 3 insert beneath and medial to the insertion of part 1.

maxillomandibulary = a small, rounded, dorsoventrally compressed bone in Neostethidae lying in the maxillomandibulary ligament near the tip of the lower limb of the premaxillary.

maximum constant yield = the maximum constant catch sustainable for all probable future levels of stock biomass.

maximum economic performance = a fishery producing the maximum amount of economic benefits; the sum of net benefits to fishers and consumers, and resource rent.

maximum economic yield = the total amount of profit that could be earned from a fishery if it were owned by an individual; the yield above which the revenue generated by a marginal increase in effort is less than the cost necessary for the attainment of that increase. May be measured in dollars or weight. Abbreviated as MEY.

maximum fishing mortality threshold = the rate of fishing mortality, that if exceeded, will result in overfishing and jeopardize the capacity of a stock to produce maximum sustainable yield on a continuing basis. Abbreviated as F_threshold.

maximum potential yield = the largest harvest that can be maintained from a population or area under optimal population and environmental conditions.

maximum spawning potential = spawning potential ratio, q.v., or % MSP (the ratio of spawning potential per recruit under a given fishing regime relative to the spawning potential per recruit with no fishing).

maximum standing crop = maximum abundance of fish sustainable by a water body without loss or gain in weight taking into account natural or artificial food availability.

maximum sustainable yield = the average or maximum catch that can be removed under existing environmental conditions over an indefinite period without causing the stock to be depleted, assuming that removals and natural mortality are balanced by stable recruitment and growth. In fisheries, this method was an effort to take all the fish that the fishery could supply on a continuous basis. However it did not work out on a practical basis as good years were mixed with bad years (more or less production than the simple theories predicted) and prediction of the maximum sustainable yield was difficult. Overestimates or a series of bad years will cause a fall in biomass. The fishery will have to be reduced while the stock recovers. More conservative methods are now used (see optimum sustainable yield). Abbreviated as MSY or Y_s. Also called maximum equilibrium catch, maximum sustained yield, sustainable catch.

maximum sustained yield = strictly this is the yield that can be sustained without depletion of the stock. Maximum sustainable yield is then the maximum catch that can be made per unit time under the appropriate fishing rate, and presumably cannot be sustained indefinitely.

maximum yield-per-recruit = maximum expected lifetime yield per fish recruited in the stock.

May parr = a salmon parr before it descends the river as a smolt in May (Scottish term).

maze = 1) to have the maze is said of herrings about to shoot the roe (British dialect).

mbipi = haplochromine cichlids endemic to Lake Victoria, the equivalent of Lake Malawi's mbuna.

mbuna = the African word for "rockfish", a group of colourful, herbivorous, reef-dwelling haplochromine Cichlidae in Lake Malawi.

McFish = Filet-O-Fish (a MacDonald's fish sandwich introduced in 1963 to combat declining sales on Fridays, a non-meat eating day for certain Christians. Also popular with Muslims who cannot eat haram meat. Also called FishMac).

meal = dried fish or fish waste used as fertilizer, animal food or ground fine for use in soups. May be defatted, and is powdered or granular in form.

mean biomass = the product of mean abundance (numbers) and the average weight of individual fish. The former is calculated from abundance at the beginning of the year and the annual mortality rate and the latter are derived from population size and weight at age data.

mean generation time = the average time it takes for a sexually mature female to be replaced by an offspring with the same reproductive capacity.

mean high water = the average elevation of all high waters recorded at a particular station, usually over 19 years. Shorter terms may be used but are readjusted to eliminate variability and give a result equivalent to the 19-year value. All high water heights are included in the average where the type of tide is either semidiurnal or mixed. Only the higher high water heights are included in the average where the type of tide is diurnal (in which case mean high water is the same as mean higher high water).

mean higher high water = the arithmetic average of the elevations of the higher high waters of a mixed tide over a specific 19-year period.

mean high water springs = the average height of the high water occurring at the time of spring tides.

mean low water = the average height of the low waters over a 19-year period. Shorter terms may be used but are readjusted to eliminate variability and give a result equivalent to the 19-year value.

mean low water springs = the average height of the low waters occurring at the time of the spring tides.

mean lower low water = the average height of the lower low waters over a 19-year period. Shorter terms may be used but are readjusted to eliminate variability and give a result equivalent to the 19-year value.

mean range of tide = the difference in height between mean high water and mean low water.

mean rise of the tide = the height of mean high water above the plane of reference or datum of chart.

mean sea level = the mean surface water level determined by averaging heights at all stages of the tide over a certain period, usually a 19-year period. Usually determined from a fixed predetermined reference level or chart datum.

mean tide level = half-tide level (plane midway between mean high water and mean low water).

mean water level = the mean surface level as determined by averaging the heights of water at equal intervals of time, usually hourly.

meas(e) = 1) a measure used in counting herrings of varying quantities. Usually about 500-620 herrings and may be accurately 612 fish. Also spelled mais, maise, maize and maze.

measure = 1) the act of unloading herring and assessing that boat's catch (Scottish dialect).

measure of the fish = the length-height ratio of the vesica piscis, q.v., as expressed by Pythagoras is 153:265, a mystical number.

meat = the flesh of animals used as food. Not generally applied to fish but does occur, e.g. shark meat.

meat ball = a small school of bait fish that form a ball in the water as an instinctive response to a predator. Also called bait ball.

meat hole = angler slang for a place where fishing is very good and easy, attracting many anglers.

mechanic(al) narcosis = stunning fish for food by vibrations. Clubs can be used to bang on ice of the appropriate thickness (not too thick and slightly brittle) to stun fish just below, or on rocks to stun fish hiding underneath them. Thrown objects from rocks to boomerangs used to stun fish would also fall in this category as would bullets (meant to stun not hit) and explosives.

mechanical brining = brining (q.v.) fish with mechanical conveyers and/or pumps and controls.

mechanical filtration = elimination of particulate matter in aquaria, e.g. by means of polyester pads.

mechanical intensity of fishing = fishing effort (the total fishing gear in use for a specified period of time; when two or more kinds of gear are used, they must be adjusted to some standard type before being added, or effective fishing effort, abbreviated as f or f (Ricker, 1975)).

mechanically recovered fish flesh = the flesh of a fish separated from skin and bones by mechanical means (see bone separator). Also called minced fish, recovered flesh, recovered fish flesh, boneless fish meat and deboned fish.

mechanised pole line = an automatic fishing line and pole which moves the hook up and down while fishing, brings the captured fish onboard, releases it from the hook, baits the hook and redeploys it in the water, e.g. in tuna fishing.

mechano-receptor = organs allowing fish to sense currents and its own movements, mainly in the lateral line system.

Meckel's cartilage = the functional lower jaw of Elasmobranchii and Holocephali, the embryonic lower jaw of other gnathostomous vertebrates which ossifies at least in part as the mentomeckelian, mediomeckelian, coronomeckelian, articular and retroarticular. It remains in some adult fishes as a pointed rod embedded in the dentary and angular. Also called mandibular cartilage, ceratomandibular cartilage or primary mandible. See also Bridge's ossicles.

Meckel's foramen = when not completely surrounded by dermal bone, Meckel's cartilage is visible on the medial face of the lower jaw, e.g. some Sarcopterygii. Also called Meckel's or Meckelian canal, groove and fossa although groove is usually used in tetrapods.

Meckel's ossicle = sesamoid articular, sesamoid angular or coronomeckelian (a small bone on the internal surface of the articular bone of the lower jaw. Often a point of insertion of the adductor mandibulae muscle).

medial = towards the vertical plane running through the middle of the body (the sagittal plane). Opposite of lateral.

medial plate = innominate bone (the pelvic fin bone in Gasterosteidae, sometimes a misnomer for the ectocoracoid. Also called pelvic bone, pelvic plate, posterior process and pubic bone).

median = 1) in or at the middle, situated on the vertical plane running through the middle of the body (sagittal plane).

median = 2) the middle value of the set when they are ordered by rank, i.e. 50% of the values are above the median and 50% are below.

median cerebral vein = one of two veins draining blood from the posterior braincase into the lateral head vein, q.v.

median fin = one of those fins located on the sagittal plane of the body, the dorsal, caudal and anal fins. Also called perissopterygium.

median length = fork length (the distance from the most anterior point of the body to the deepest point of the fork in the caudal fin. Abbreviated FL. Mostly used in fishery biology and not in systematics).

median lethal dose = the dose of a chemical which will result in the death of half the fish in a given time period. Abbreviated as LD₅₀.

median lethal time = the time over which an administered chemical will result in the death of half the fish for a given dose. Abbreviated as LT₅₀ (note that LT₅₀ is also the temperature lethal to 50% of an exposed population (or where 50% survive)).

medicated feed = feed in aquaculture or aquaria with drugs or antibiotics added as a treatment. Often strictly regulated by law.

medicinal fish = various fishes and fish parts have been used in cultures world-wide as perceived cures and treatments for ailments. Numbfish (Torpedinidae) applied to the temples cured headaches; sole placed over the site of the spleen helped alleviate splenitis; remoras delayed birth; shark's teeth rubbed across the gums of children helped teething, produced sound incisors and a shark-like appetite; livers were applied topically in various diseases and in treatment of fever and dropsy; red herrings rubbed on the body cured rheumatism; cramps and sprains were cured with an application of fresh eel skin; an eel will cure fever; deafness was cured by a powder of eel's liver; toothache by carrying around a piece of a dogfish that had been returned alive to the sea; jaundice by application of a split tench (which must then be buried; haemorraghes stopped by the brains of fish; whooping cough by putting a live fish in the mouth although it must not be swallowed; and so on.

mediolateral = middle of the side; the horizontal axis oriented perpendicular to both the anterior-posterior and dorsal-ventral axes.

mediolateral intercalation = ordered cellular repacking along the mediolateral axis by interdigitations of deep cells during the gastrula and early segmentation periods producing convergence and extension.

mediolateral photophores = old name for SAO photophores, a sloping, ventro-lateral row above the anal fin in Myctophidae.

medioparietal = a skull where the parietals touch on the midline, not being separated by the supraoccipital (as opposed to lateroparietal, q.v.).

medithermal = the current climatological conditions, beginning about 4500 years ago.

medium-salted fish = fish cured with 20-28 parts of salt to 100 parts fish by weight; the product contains 30-40% salt on a dry weight basis. Also called half-salted fish.

medium-wire hook = an all-purpose hook made from wire of medium gauge, intermediate between fine-wire and forged hooks.

medular cavity = the first vascular cavity in the median position in long bones such as spiny rays.

medulla oblongata = the hindbrain, equivalent to telencephalon (see brain). The posterior fourth ventricle is the open chamber in its dorsal half, roofed by the tela choroidea.

meese = the use of the relative positions of landmarks to determine a particular fishing spot at sea (Caithness dialect).

megafauna = very large animals, mostly whales in water but conceivably some of the larger fishes could be included. See also charismatic megafauna.

MEI = morphoedaphic index ( an index of potential fish production in lakes. Calculated by total dissolved solids (mg/l)/mean depth in metres).

meikotsu = soft bones of elasmobranchs cut into pieces, boiled, then cooled in water. The remaining muscles and hard bone are removed, and then the preparation is boiled again and dried in the sun (Japan). Exported to China.

melamine = a trimer of cyanamide and a metabolite of the pesticide cyromazine. It is used to produce countertops, glues, fabrics, inks, flame retardants, fertilisers and plastics. Melamine was found as a contaminant in wheat gluten from China that was used in pet food and in aquaculture feed in 2007. Melamine can lead to crystal formation that damages the liver among other effects, and cats and dogs have died from the contaminated food.

melanin = indole compounds which give skin its black, grey or brown color. In deeper layers of skin under turbid pigment-free layers, melanin may give rise to Tyndall blue colors. Distributed in melanophores. Melanin is formed from oxidized and polymerized end-products from the metabolism of tyrosine and allied phenolic compounds.

melaniridosome = an association of pigment cells consisting of a central melanophore surrounded by guanophores, or covered on its two faces by a syncytium of guanophores.

melanism = overproduction of the dark pigment melanin leading to an abnormal dark colouration. Occurs in nature but artificially bred in aquarium fish species. Melanistic individuals are les robust than the normal fish and are more likely to become blind or develop tumours.

melanomacrophage centre = found in the liver, kidney and spleen, these structures increase in number during stress or disease.

melanophore = a black chromatophore (capable of producing yellows and brown when pigment is thinly dispersed).

melanosis = blackening, e.g. a symptom of whirling disease (q.v.) due to vitamin B deficiency.

mell = 1) a hammer used for stunning salmon and for casting lots for stations in halve net fishing (q.v.) or positions for poke nets (q.v.) (Scottish dialect).

melker = milker herring (Dutch cured herring with the gonads left in the fish. Usually packed in small barrels with about 12 fish for the North American delicatessen trade. Also called Norwegian milker).

membrana branchialis (membran� branchiales) = opercular membrane (the tissue covering the gills laterally and enclosing (including in some, but not other definitions) the opercle, preopercle, subopercle and interopercle bones. In most Teleostei, where the membranes from each side meet under the head on the isthmus, the left side overlaps the right).

membrane bone = a bone which arises directly from connective tissue membranes without cartilaginous precursors. Includes dermal bones, as opposed to cartilage ones. Membrane bones are thin, laminar and located near the surface of the body. When the connective mesenchyme transforms into bone it does not differ histologically from bone which arose from cartilage. Also called achondral, dermal (q.v.), covering and investing bone.

membranopterotic = supratemporal-intertemporal (a dermal bone overlaying the pterotic (or autopterotic). Also called intertemporal or dermopterotic).

membranous labyrinth = the semicircular canals and the appended otosac. The canals and chambers are filled with endolymph and surrounded by perilymph. The membranous labyrinth is enclosed in cartilage in Cyclostomata and Elasmobranchii, in several bones in Teleostomi, the bony labyrinth.

memory = the annoying tendency of fishing line on a spool to take up the spool shape and to come off it in coils that tangle easily and cast poorly.

mend = in fly fishing, throwing an upstream curve in the fly line to compensate for the current so that the fly is presented at the same speed and direction as the current. Trout are very sensitive to food items and artificial flies not moving in tune with the natural flow. Also used in float fishing to keep the float trotting in a straight line.

menhaden = Brevoortia tyrannus, the common name meaning fertiliser in Algonquian as it was so numerous that it was buried in corn fields.

meniscus = a disk of cartilage located in a joint between the surfaces of articulating bones.

mental = 1) relating to the chin. Most common use in fishes, e.g. mental barbel.

mental appendage = a fleshy globe or membranous tassel on the tip of the chin; used as an organ of touch.

mental crest = an outgrowth of the dentary bone of the lower jaw. The crests from each side of the lower jaws converge anteriorly. Also called chin or submental crests.

mental foramen = a hole or channel in the mandible leading to the Meckelian fossa.

mentomeckelian = the ossified tip of Meckel's cartilage. It fuses with the dentary in most Teleostei but is independent in Cyprinidae. Found in Amia and perhaps larval Salmonidae. Also called mentomandibular.

merchant = an entrepreneur in the Newfoundland cod trade who finances fishing operations through the advance of supplies and credit.

merchantable cod = split, salted and dried cod of a quality suitable for sale as opposed to refuse cod, q.v.

merchantocracy = the merchants of St John's, Newfoundland, engaged in the export of cod and the provisioning of fishermen.

mercury contamination = many fish species, both freshwater and marine, caught by sport fishermen are contaminated by mercury. Advisory levels for consumption are issued by government agencies.

mere = a small lake, pond or marsh, usually a sheet of shallow standing water (Saxon). Other definitions have a mere as a small, deep piece of water, especially if a river runs through it.

meristic = pertaining to serially repeated structures, e.g. scales, vertebrae, fin rays, fin spines, other spines, myomeres, photophores, scutes, finlets, branchiostegals, and also to other structures that can be counted, e.g. pyloric caeaca, etc. Also used as a noun and usually in the plural.

meristogram = a graph showing the variation in the number of meristic characters between specimens and populations.

mermaid = a mythical piscine humanoid, the upper portion being that of a female human, the lower that of a teleost.

mermaid's purse = an egg-case of an Elasmobranchii, usually oblong with horns or tendrils.

meroblastic = an egg of which only part undergoes cleavage - usually one with a large amount of yolk which is not incorporated into the developing egg, e.g. in Myxini, Elasmobranchii, Holocephali, many teleosts.

meroblastic cleavage = cell division in which sister cells are only partially separated from one another by cytokinesis. Also called incomplete cleavage.

meromictic = a permanently stratified lake, usually without oxygen (and fish) in its deeper portions, due to a density gradient and a lack of turnover.

meropelagic = said of organisms that are only temporary members of the pelagic community.

meroplankton = planktonic eggs and larvae which are temporary members of the plankton, including many fishes.

merotype = a portion of the holotype that has been detached and is kept separate after the original publication. Probably more a botanical term but could apply to fishes where scales, pharyngeal teeth and other structures are removed for a later study.

mesell = infected, diseased or tainted fish. Also spelled mesal, mesall, messale, missael, mysel, mysell, mysaell and mysale.

mesencephalon = the midbrain, one of three regions that develop in the fish brain. Unlike the forebrain and the hindbrain, the mesencephalon remains undivided. Details of the brain structure of a fish (Danio rero) may be found in Wullimann et al. (1996). See also brain.

mesendoderm = hypoblast (the inner of two layers of the blastoderm that forms during gastrulation and gives rise to the mesoderm and endoderm).

mesentery = double membranes meeting in the midline above and below the viscera formed by the serous membranes in the peritoneal and pericardial cavities. The mesentery in the pericardial cavity disappears during embryonic development and most the the ventral mesentery is lost in the peritoneal cavity except for falciform and gastrohepatic ligaments (q.v.).

mesethmoid = a term misapplied to the ethmoid (q.v.); the fish structure is not homologous with that in mammals.

mesh = 1) the opening in a net, bounded by the material from which the netting is made.

mesh = 3) to knit or make the sides, bottom and leader of a cod trap (Newfoundland).

mesh cut = t-cut (a cut in netting parallel to the general course of the netting).

mesh opening = the inside distance between two opposite knots (in knotted netting) or joints (in knotless netting) when fully extended.

mesh selection = fish above a certain size are unable to pass through a net of a certain mesh size while smaller fish can escape.

mesh size = the stretched length from corner to corner of the mesh of a net, i.e. the size of the holes, used to denote size of a net. Often regulated to allow young to escape.

meso-larva = a larval stage in which at least one, but not all, of the distinct principal rays of the median fin is apparent or, if the full complement is present and the adult possesses pelvic fins, the pelvic buds or fins are not yet apparent.

mesocoracoid = a paired pectoral girdle endochondral bone between the cleithrum dorsally and the coracoid and scapula ventrally.

mesohabitat = pools, runs, riffles or parts of lakes, cf. macrohabitat and microhabitat.

mesohaline = 1) pertaining to brackish water with a salinity between 3 and 10 parts per thousand or sea water between 30 and 34 parts per thousand.

mesohaline = 2) water with a salinity of 5.1-18.0 p.p.t. derived from ocean salts and pertaining to organisms able to live there.

mesomere = 1) a mesodermal component, a blastomere of intermediate size, larger than a micromere but smaller than a macromere.

mesomere = 2) the middle zone of the mesoderm of a chordate vertebrate embryo, from which excretory tissue develops.

mesomere = 3) a median series of bones supporting the pectoral fin in Sarcopterygii fish.

mesonephros = the functional organ of excretion with a large number of tubules in all adult fishes except Myxini. Arises in the middle portion of the body cavity but extends backwards to the entire length of body cavity, and is deflected ventrally on the posterior body wall to end on the posterior surface of the bladder. The mesonephros is a paired structure but may fuse posteriorly while separated anteriorly by the dorsal aorta. Anteriorly the mesonephros is expanded into a head kidney made up mainly of blood sinuses.

mesopelagic = pertaining to the midwaters of the ocean between 200 and 1100 (or 100-1000m or 150-2000) metres (sources differ). Generally characterized by dim light and steep temperature gradients.

mesoplankton = members of the plankton between 1 mm and 1 cm; not used much as it can be confused with plankton living at mid-depths.

mesopterygium (plural mesopterygia) = the median, elongated basal cartilage of the pectoral fins in Elasmobranchii, Holocephali and primitive Teleostomi.

mesopterygoid = metapterygoid (the deep, paired, endochondral bone forming the posterior end of the palatoquadrate and connected with the hyomandibula. Absent in many modern Teleostei. Also called endopterygoid and entopterygoid).

mesosaline = 2) water with a salinity of 5.1-18.0 p.p.t. derived from land-derived salts.

mesotrophy = pertaining to waters having intermediate levels of primary productivity.

Mesozoic = a geological era ca. 245-65 million years ago, comprising the Cretaceous, Jurassic and Triassic periods.

met(t) = a measure, such as one or two bushels or a barrel, e.g. of herrings (British dialect).

meta- (prefix) = after, between, among, change, transformation, distal to, beyond, behind.

meta-larva = a larval phase in which the full complement of distinct principal rays in the median fish and pelvic fin buds or fins are apparent.

metabolic coefficient = the metabolic relationship between fishes under various conditions, usually between fish of different size, different species, at various activity levels, or under various environmental conditions.

metabolic rate = the amount of oxygen used per unit of body weight over a time unit.

metacleithrum (plural metacleithra) = postcleithrum (plural postcleithra)(a dermal bone of the pectoral girdle posteroventral to the cleithrum which supports it dorsally. There may be one to several postcleithra (absent in some species). Also called postclavicle).

metahaline = waters containing between 36 and 40 parts per thousand of dissolved salts. See also euhaline and Venice system.

metal halide light = a white, hot, incandescent and fluorescent lighting for aquaria, particularly for reef tanks. It produces a wide spectrum of light and closely simulates natural light.

metalimnion = a zone of abrupt temperature change (thermocline) between the warm epilimnion and the cool hypolimnion of a lake.

metamorphosis = a major structural change taking place during development from larvae to adult, e.g. Anguilliformes, Molidae.

metapleure = ventrolateral skin folds extending from the mouth to the atriopore, where they join to form the caudal fold in Amphioxi.

metapopulation = a set of partially isolated populations of the same species able to exchange individuals and recolonise sites where the species had become extirpated.

metapterygial whip = an elongate and thin extension of a fin based on the metapterygium.

metapterygium (plural metapterygia) = the posterior and innermost basal cartilage in the paired fins of Elasmobranchii and Holocephali. It is usually the longest basal and is exceptionally long in males where it is distally modified into a clasper, q.v.

metapterygoid = metapterygoid (the deep, paired, endochondral bone forming the posterior end of the palatoquadrate and connected with the hyomandibula. Absent in many modern Teleostei, it bears teeth in the Albulidae. Also called mesopterygoid, endopterygpoid and entopterygoid).

metatype = 1) a specimen from the type locality determined by the original author subsequent to the original description of the species.

metatype = 2) a specimen subsequently determined by the author after comparison with type.

metaxymiost = a rib-like bone (but not a rib) formed in the intermuscular septa. Dorsally called epineural bones, centrally epicentral bones and ventrally epipleural bones (more or less related to the vertical ribs). Also called intermuscular bones.

mete fish = freshly caught fish sold for immediate use rather than being salted or packed in barrels (Scottish dialect). Also spelled meit fish or meat fish.

metencephalon = the anterior part of the hindbrain. Gives rise to the fourth trochlear motor nucleus, the cerebellum dorsally and the interpeduncular nucleus ventrally. Details of the brain structure of a fish (Danio rero) may be found in Wullimann et al. (1996). See also brain.

methaemoglobinaemia = the combination of haemoglobin and ammonium nitrate in fish blood causing brown blood disease or nitrite poisoning. Occurs under conditions of poor water. Nitrite oxidises the iron in fish haemoglobin to produce a molecule called methaemoglobin, which unlike haemoglobin, can�t carry oxygen around the blood. This process causes extreme breathing difficulty or even suffocation. Nitrite also builds up in the blood causing poisoning, and may lead to liver, gill and blood cell damage.

method feeder = a central tube with three fins through which fishing line is threaded. A sticky form of ground bait, q.v., is moulded around the feeder and the hook with its bait is buried in the ground bait. Fish coming to eat the ground bait will also eat the hook - this is so effective it has been banned at some British contests.

methylene blue = a dye (3,7-bis (Dimethylamino) phenazathionioum chloride) used against external bacteria and protozoans on fish.

methyostyly = a derivation of hyostylic jaw suspension in that the hyomandibula still plays a role in jaw suspension, but in this case the original elements have been replaced by dermal bone, and the hyomandibular is a reduced element at the jaw joint, e.g. in bony fishes.

metonymous homonyms = homonyms based on different nomenclatural types but which are considered to belong to a single taxon.

metric ton = tonne; 1000 kilogrammes, 0.984 long tons, 1.1023 short tons or 2204.6 pounds. Abbreviation MT, mt or t.

meuni�re = all kinds of fish can be cooked � la meuni�re. The fish is coated with seasoned flour, fried in butter and served with melted butter, lemon juice and herbs.

MEY = maximum economic yield (the total amount of profit that could be earned from a fishery if it were owned by an individual).

mho = abbreviation for conductivity, q.v., measured in mhos (reciprocal ohms - mho is ohm backwards) (siemens is the metric version).

micro shot = very small split shot, q.v., used with very sensitive pole float rigs. Sizes are from number 8 (small) to number 16 (minute). This shot enables the rig to sink slowly thereby catching any fish from the surface down to the bottom. Used particularly to catch small fish during matches.

micro-branchiospine = one of a series of small dermal ossifications, each bearing 5-20 tiny lateral spines, located on the outer face of each gill arch except the first near the base of the gill filaments as in Tilapia (Cichlidae). They may sieve out phytoplankton or protect the gills from abrasion by fine particles. Micro-branchiospine-like structures are found in Centropomidae, Pomadasyidae and Gerreidae due to homoplasy.

micro-climate = the climate of a small, specific place within an area as contrasted with the climate of the entire area. Often inhabited by a unique assemblage of species.

micro-encapsulated diet = feeding small, particulate formulated feed in aquaculture to fish larvae. The feed is enclosed in a capsule of different material (a membrane or binder) from the contained feed.

microbarb= a very small barb on a hook in designed to lessen damage to fish and to small baits such as maggots.

microbound feed = a particulate, formulated feed in aquaculture for fish larvae. The particles are 50-700 μm and are held together by an internal binder made of complex carbohydrate or protein with a adhesive and absorptive properties.

microconstituent = the elemental makeup of bones. These can be used in fishes to determine life history, e.g. deposition of elements in fresh water is different from that in the sea.

microencapsulated feed = small, particulate formulated feed in aquaculture for fish larvae. The feed is enclosed in a capsule of different material (a membrane or binder) from the contained feed.

microhabitat = 1) an area somewhat larger than the fish itself, cf. mesohabitat and macrohabitat.

microhabitat = 2) a portion of a larger habitat. Selected by a fish for specific purposes and separated from adjoining microhabitats by physical characteristics such as depth, cover, velocity, etc.

microincrement = growth increments less than 50 μm in otoliths or other structures used in ageing, only observable with a microscope and used to describe daily or shorter increments.

microincrement scale = a scale present from the early life history of a fish which has not been resorbed.

micromelanophore = a minute type of melanophore about 1/3 or less the diameter of a normal-sized melanophore (or macromelanophore). May be inherited independently from macromelanophores.

microparticulate diet = very small food particles manufactured for larval fish in aquaculture.

microsatellite = a very short unit sequence of DNA (2 to 4 base pairs) that is repeated multiple times in tandem. Microsatellites are highly polymorphic and make ideal markers for analysis of relationships.

microsmatic = forms with poorly developed olfactory sense, e.g. Esox, Exocoetidae, Gasterosteidae. Opposite of macrosmatic, q.v.

microsporidial infection = infection of fish with any sporozoan member of the Protozoa considered to be a microsporidian.

microsquamose = having very small scales, e.g. in the extinct thelodonts, presumably jawless vertebrates known mostly from their minute scales.

microstructural growth interruption = deposition of organic material interrupting growth of crystallite in an otolith.

microtag = a coded tag of very small size capable of being inserted into a fish to track that individual as well as attached externally.

microworm = a food for aquarium fry and smaller fish species. Microworms, Anguillula silesiae, are a type of nematode usually found in decomposing fruits and are about 1-3 mm in length. They can be cultured in trays of wet oat meal kept at a temperature of around 25�C in a dark location. Yeast may be added to encourage fermentation.

mid-brain = the area of the larval fish brain that includes the optic and cerebellar lobes. Also called mesencephalon.

mid-caudal length = fork length (the distance from the most anterior point of the body to the deepest point of the fork in the caudal fin. Abbreviated FL. Mostly used in fishery biology and not in systematics).

mid-extreme tide = a plane midway between the extreme high water and the extreme low water occurring in any locality.

midden = a rubbish heap of domestic waste, including fish bones which enable past diets to be determined.

middle = a large piece of dried salted cod obtained after the nape, tail and thin part of the belly have been removed. Also called steak.

middle course = the stretch of a river between the upper and lower parts, below the trout zone and above the bream zone (both q.v.).

middle distance = the fishery or the vessels engaged in the fishery, between the local inshore and the distant offshore sectors (Newfoundland).

middle twine = lint (netting in the main body of a drift or gill net. Also called body, middle yarn, netting, sheet, webbing, yarn).

middle yarn = lint (netting in the main body of a drift or gill net. Also called body, middle twine, netting, sheet, webbing, yarn).

middle-level consumer = second-level consumer (a fish that feeds on other animals that themselves feed on plants).

middleground shoal = a shoal formed by ebb and flood tides in the middle of a channel of the lagoon or estuary end of an inlet.

middleman = a fisherman and owner of fishing premises and vessel who is supplied by a merchant and engages a crew on the share system (Newfoundland).

midshipman = a fisherman occupying the midship position in an undecked boat (Newfoundland).

midwater = pertaining to the mesopelagic zone; any part of the water column between the surface and the bottom.

midwater drift = operation of gillnets between the bottom and the surface of a water body.

midwater trawl = a net towed through the water column by one boat, the net being positioned above the bottom and below the surface. It may have otter doors that function to keep the net mouth open and depressor plates that function to make it fish deeper, or two vessels pair trawling keep the mouth open. The front net sections are often made with very large meshes or ropes, which herd the fish schools towards the net aft sections. The fishing depth is usually controlled by means of a net sounder (netsonde). Also called midwater otter trawl.

midwater pair trawl = a net towed through the water column by two boats, thus ensuring the horizontal opening of the net. Such nets are designed and rigged to work in midwater. Surface trawls are also included in this category.

miette = a small piece of tuna meat obtained when the cooked fish is cut into slices. This term is only permitted for tuna products (France).

migaki-nishin = herring pan-dressed and cut into fillets, then dried in the sun without salting (Japan).

migraine = easily cured by tapping the head with a fish according to ancient Egyptian physicians.

migration = 1) a directed (not aimless) journey and return occurring regularly in a species, usually at a definite stage in the life cycle, e.g. anadromous, catadromous, diadromous, amphidromous, potamodromous, oceanodromous, all q.v.

migration = 4) in flatfishes, the movement of one eye to the other side of the head involving crossing of the optic nerves in the optic chiasma.

migratory fisherman = a fisherman who travels to offshore or distant waters to catch fish.

mihi = belonging to me, of me (as of authorship of a new species, or used to show the writer's responsibility for a statement or proposal).

mild smoked fish = fish smoke-cured for a short period to give a slightly smoky flavour; has limited keeping quality. Also called light smoked.

milk bush = Euphorbia tirucalli, a thorny Indian bush, often used as hedges, which has an acrid milky sap used in poisoning fish.

milk soup = a soup made of milk, bread or rice, or with flaked white fish and milk. Can include chopped hard-boiled eggs and parsley.

milker herring = Dutch cured herring with the gonads left in the fish. Usually packed in small barrels with about 12 fish for the North American delicatessen trade. Also called melker or Norwegian milker.

milkiness = murky or liquefied flesh in such species as hake, halibut and wild and farmed salmonids. Myxosporeans (Kudoa spp.) secrete a proteolytic enzyme causing unsightly white cysts in the flesh and, in extreme cases, softening and liquefaction. Cysts become evident if the fish is smoked.

mill = a circularly swimming mass of fishes, usually formed only by obligate schoolers.

mill dam = a dam across a river used to back up water and make it available for a mill.

mill pond = the pond formed by damming a stream to create a head of water to run a mill.

milt = 1) the seminal fluid; male gonads (testes). Marketed fresh or canned, particularly from herring and mackerel and called soft roe. When released into the water often creating a cloudy effect, either over a small area or in massive spawnings visible from the air.

milt sauce = milt of herring mixed with vinegar sauce and strained to remove membranes. Used for packing vinegar cured herring products.

mimicry = similarity of appearance between two species, the mimic gaining protection from resembling a dangerous organism such as a predator or poisonous organism (Batesian mimicry) or where both species are protected against predators by being distasteful and they gain mutually since predators avoid both species by tasting one (M�llerian mimicry).

min. parte = abbreviation for pro minore parte, meaning for the smaller part.

Minamata disease = mercury poisoning of humans from eating contaminated seafood such as fish.

minced fish = the flesh of a fish separated from skin and bones by mechanical means (see bone separator). Also called mechanically recovered fish flesh, recovered flesh, recovered fish flesh, boneless fish meat and deboned fish.

minimum biological acceptable level = 1) a value of spawning stock biomass below which the probability of reduced recruitment increases as spawning stock size decreases.

minimum biological acceptable level = 2) legislated size below which individuals of some fish species, if caught, are not to be retained.

minimum landing size = the smallest length at which it is legal to keep or sell a fish. May not be the biologically optimum size but a market size.

minimum legal size = a regulation where captured fish smaller than a set size must be returned to the water.

minimum lethal dose = the smallest amount of a lethal compound sufficient to kill all of the test animals.

minimum mesh size = the smallest legal mesh size used for a given type of net (measured across the diagonal under tension).

minimum protein level = the level of protein in a fish diet ensuring adequate growth and lowest cost commercial production.

minimum size = regulations as to catches of fish by forbidding takes below a minimum size.

minimum stock size threshold = the minimum size of the stock that is required to produce maximum sustainable yield, below which the stock would be considered overfished. Abbreviated as B_threshold.

miniaturization = the evolution of small size, e.g. in various cyprinid and gobiid fishes. Paedocypris progenetica, a cyprinid, is arguably the smallest fish and vertebrate at 7.9 mm standard length and Schindleria brevipinguis, a gobiid, has males mature at only 7 mm.

Minister's dog = a Tweed River, Scotland, salmon fly made originally from the yellow hairs of a dog belonging to the minister of Sprouston in 1915.

minnie = a stone on the end of a rope plunged repeatedly into the mouth of a pilchard seine net to prevent fish from escaping (Cornish dialect).

minnow = 6) in angling, a long thin plug or a shallow diving plug retrieved by a series of fast pulls and jerks.

Minnow = 7) the S.S. Minnow was the stranded boat in the television show "Gilligan's Island".

minnow bucket = a metal, plastic or styrofoam bucket with a lid used to transport bait fish alive for angling.

minnow trap = a simple trap of metal or plastic in two equal halves, joined at the middle with a catch. The trap can be sunk in water of any depth and marked by an attached line and float. It has an inward-directed, narrowing cone that fish can enter but find difficult to locate and leave through. The trap can be baited and is used for catching small fishes used in bait fishing and in scientific surveys of smaller species. Glass minnow trap jars are also made and sold.

minnow zone = grayling zone (an area of a river lying between the trout and the barbel zones (both q.v.) characterised by alternating rapid and moderate currents).

minnow-saver = a chemical additive for tap water to remove chlorine and copper and keep bait fish alive longer in a minnow bucket.

minor carp = smaller carp species (Cyprinidae) as opposed to the Chinese and Indian major carps, q.v.

mirin-boshi = split fish usually without the head, dried after soaking in seasonings consisting of either soy sauce, sugar and sweet rice liquor (mirin), or salt, sugar and gelatine or agar (Japan).

misapplication = the use of a scientific name for a taxon which does not include the type within its range of variation; to apply, deliberately or otherwise, a name in a sense which is not correct under the provisions of the International Code of Zoological Nomenclature, e.g. in a manner not in accord with the name-bearing type.

misapplied name = a name given to a taxon which excludes the nomenclatural type of the name.

misreporting = inaccurate catch recording in log books or other official reporting systems by under-reporting the catch or misrepresenting the area fished.

Miss Katie = a fishwife who sold dried fish at fairs and markets (Scottish dialect).

mitochondrial DNA (mt DNA) = a form of DNA, the chemical basis of heredity, found in the mitochondria (or energy producing structures within cells) and used to identify and relate fish species.

mixed culture = aquaculture involving raising fish of different species or ages in the same water body.

mixed fertiliser = having more than one of three major nutrients, nitrogen, phosphorus and potassium.

mixed stock = a stock composed of native and non-native parents or a native stock that has undergone substantial genetic alteration.

mixed stock exception = where many species of fish occur together, some may be overfished while others are being harvested in a sustainable fashion. If these mixed stocks were managed on the basis of the overfished stock then no fishery could occur - an exception is made and some overfished stocks are allowed to be caught.

mixed tide = a type of tide intermediate to those predominantly semidiurnal and diurnal.

mixing rate = the speed at which water masses in a reservoir are mixed during seasonal circulation (turnover).

mixoeuhaline = pertaining to estuarine waters containing more than 30 p.p.t. of dissolved salts but less than the concentration of the open sea.

mixohaline = brackish water, water of intermediate salinity, 0.5-30.0 p.p.t. from ocean-derived salts.

mixolimnion = the uppermost region in a meromictic lake with free circulation and capable of supporting fish.

mixomesohaline = said of brackish water containing from 5 to 18 p.p.t. dissolved salts.

mixooligohaline = said of brackish waters containing from 0.5 to 5 p.p.t. dissolved salts.

mixopolyhaline = said of brackish water containing from 18 to 30 p.p.t. dissolved salts.

mixosaline = brackish water, water of intermediate salinity, 0.5-30.0 p.p.t. from land-derived salts.

mobile = fish which normally range widely, e.g. beyond 1.6 km of the point of release. Opposite of sedentary, q.v.

mobile fishing gear = 2) any gear that can be moved from place to place, even gear that is fixed when operational.

mobile impoundung net = a net not attached to the bottom, easily moved around, only fishes when moved through the water.

mode = the value which occurs at the highest frequency, e.g. fin ray counts often have strong modes, characteristic of a species.

modified release = a marine fishing tournament in which only fish below a certain size are released.

moggi(e) = the stomach of a fish or whale (Shetland Isles dialect). See also cropping moggies.

mohan = a northern Indian word for a variety of fish poisons including cactus sap (Euphorbia rogleana), crushed seeds of Cascaria tormentosa and Xanthoxylum alatum (toothache tree, Rutaceae), and boiled tea leaves mixed with lime.

mohua = a fish poison, the alkaloid saponin, from the powdered seeds of Bassica latifolia (India).

moist pellet = a pellet used in aquaculture with a moisture content around 30%. Composed of wet ingredients such items as minced fish, and dry ingredients such as fish meal, cereals, vitamins and minerals, with an alginate binder. Also called Oregon moist pellet.

mojo rig = a rig similar to a Carolina rig except fished on a spinning rod and so is a finesse (q.v.) method. The sinkers are cylindrical or pencil-shaped so that they do not snag on rocks.

molar = a large flat or ridged-topped tooth adapted for crushing or grinding, e. g. in Anarhichadidae.

molariform = shaped like a molar in mammals, being rounded and flattened. Molariform teeth are used for crushing molluscs and crustaceans.

mole = a very large solid-filled structure protecting or forming a harbour. May provide a habitat for fish species. Also called jetty.

molecular adsorption pad = a polyester pad which has been chemically treated to absorb certain substances from the water in aquaria. The pad is contained in a canister or power filter. May remove good trace elements as well as pollutants.

molecular systematics = the study of molecular biological diversity within and between taxa.

molesting = any interference with fish other than legal means of capture. Includes injury inflicted on fish meant to be released.

mollag = a dog's skin blown up as a bladder and used as a buoy to float herring-nets (British dialect).

monandry = protogynous hermaphrodites among which all males are sex-reversed females. See also diandry.

Monday's haddie = a stale fish, one that was caught two days ago, since there is no fishing on Sunday (Scottish dialect).

money = fish have been used as money in various countries, e.g. in 1640 dried fish were acceptable as payment of taxes in parts of New England; dried cod were used in nineteenth century Newfoundland.

moniliform = resembling a string of pearls, said of the notochord in Teleostei where it is alternatively thread-like and expanded in cavities.

monimolimnion = the lower, perennially stagnant region in a meromictic lake; fishless.

monitoring, control and surveillance = activities by the fisheries enforcement system to ensure compliance with fishery regulations.

monk = a weir structure used to regulate water depth in a pond with a screen to retain fish.

monkey climber = a bite indicator used for legering; a bobbin slides up and down a metal spike to indicate bites.

monkeyfishing = using a home-made device to send a strong electrical current through the water, stunning fish which float to the surface and can be dip-netted. Illegal. Also called telephoning.

mono leader = a leader made of monofilament, much heavier and stronger than the line of the reel.

monocyclic fish = those fish which spawn once in the last stage of life (as opposed to polycyclic fish, q.v.), e.g. Oncorhynchus, Anguilla.

monoecius = containing ovarian and testicular tissue in one individual, e.g. some Sparidae and Serranidae.

monofilament = a single, untwisted synthetic line used in fishing. Usually nylon but may now be perlon or teflon.

monomictic = said of a lake having a single period of free circulation or overturn per year (usually in the fall).

monophyletic = having a single unbranching line of evolution. A monophyletic taxon includes all descendents from the common ancestor of its members. A "monophyletic group" usually refers to a clade, i.e. an organism and all of its descendants.

monosex culture = the use of a single sex in fish culture to prevent uncontrolled reproduction and to reduce size variability in the product.

monospondylous = vertebrae with only one centrum, the typical vertebrae in Chondrichthyes and Actinopterygii.

monothetic key = a dichotomous key in which each couplet has single contrasting statements requiring simple either/or answers.

monotype = a monotypic taxonomic unit, not a name for a type but has been used for an implied holotype.

monotypic = a taxonomic unit including only one lower unit, e.g. a monotypic genus includes only one species.

monotypy = the situation arising when a genus-group taxon is established with only one originally included species. If no nominal species were included at the time a genus was established before 1931 and subsequently a single nominal species is first referred to the genus, then that species is ipso facto the type-species, by subsequent monotypy.

monstrositas = monster; huge; outrageous. Used to indicate an unusual form such as a deformity but also a form different from normal, e.g. a mirror carp with isolated large scales.

montane = mountainous; a stream characterised by a high gradient, riffles composing more than half the length and pools frequently run-like.

mooching = slowly raising and lowering a baited hook while drifting in a boat, e.g. for salmon.

moon light money = a due paid by fishermen for the right to fish for herring during the second or third quarters of the moon (Scottish dialect).

moon pool = an opening in the bottom of a ship allowing sampling without exposure to the weather conditions found on deck.

mop = an artificial, aquarium spawning medium for those fishes that deposit or scatter adhesive eggs in or over vegetation; consists of a mass of synthetic yarn tied into various configurations. See also floating (or top) mop, bottom mop and trailing mop.

morbidity = 2) the proportion of diseased fish in a population or a sample over a given time.

more fish in the sea = a proverb meaning do not be concerned about what you have lost. Often refers to lost love.

more than one way to skin a cat = usually applied to felines but in the southern United States where eating catfish (Ictaluridae) is common, applied to a fish and also meaning there is more than one way to do something.

mormyromast = one of an innervated group of cells in a round capsule at the end of a jelly-filled tube opening to the skin surface of Gymnarchidae and Mormyridae; electric sense organs. Also called snout organs or multicellular glands.

moratorium = a mandatory closure of a fishery in an area with a particular gear for a specified period of time. May apply only to new fishers or be an outright ban.

mormyrocerebellum = the greatly enlarged lobi laterales valvulae of the cerebellum which displace the optic lobes laterally and ventrally and cover the brain dorsally and laterally in the Mormyriformes. Also called gigantocerebellum.

mormyshka = a Russian lure, originally big spoons used for ice jigging, eventually becoming a a metal head of varying shape (often globose) with a hook attached. The line is passed through a hole in the head and whipped to the hook. As a result the hook is horizontal in the water with the point above the shank. Popular in Russia and Scandinavia (ice fishing countries). Now used too in summer fishing and with a baited hook. The name is from the Russian for scud (the freshwater gammarid amphipod).

morphoedaphic index = an index of potential fish production in lakes. Calculated by total dissolved solids (mg/l)/mean depth in metres. Abbreviated as MEI.

morphology = the appearance, form and structure of an organism, especially based on external characters.

morphometric character = a character based on measurement. In fish, measurements are taken on a straight line basis, not around the curve of the body with the exception of such measurements specifically intended to measure roundness, e.g. girth. Any measurement should be defined or referenced to a standard work as some may include soft parts or only be from bony margin to bony margin. Note that North American students of fishes mostly use straight-line measures between fixed points on the body, e.g. predorsal distance is from the anterior base of the dorsal fin to the tip of the snout while older European literature and some modern works use measures between verticals, e.g. predorsal distance is from a point on the flank directly below the dorsal fin origin in the mid-line of the fish. The latter methodology means that the sum of snout length, eye diameter and postorbital length equals head length, while the former methodology would not (e.g. postorbital length would be the longest distance from the orbit to the margin of the operculum and this is often at an angle, not on a mid-line). Some measurements include:-

1) Total length - from the anteriormost part of the head to the tip of either lobe of the caudal fin when that fin is normally splayed.

2) Standard length - from the anteriormost part of the snout (even when the lower jaw projects) to the end of the hypural plate (the end of the plate is found by flexing the caudal fin; in small fish it may be seen by shining a strong light through the caudal region). Standard length can be an inaccurate measurement. The end of the hypural plate is obscured by scales, flesh and caudal rays. Its position is determined by flexing the caudal fin; this flexure is taken to be the end of the hypural plate. Small fish have thin, delicate bones and the flexure may be at the anterior base of the hypural plate, at the origin of the caudal fin rays which articulate with and overlap the end of the hypural plate, or even between the last whole vertebra and the hypural plate. Large fish have a broad flexure which can give a variety of measurements by independent observers. If fish are comparatively small then strong illumination helps to discern the end of the hypural plate, in large fish this is somewhat inaccurate.

3) Head length - from the anteriormost part of the snout to the bony margin of the opercle (excluding the opercular membrane).

4) Body depth - maximum straight line depth excluding fins or fleshy and scaly structures at fin bases.

6) Head depth - from the occiput vertically to the breast or lower head surface.

7) Head width - the distance between the opercles when in their normal, closed position. The opercles are gently pressed into a closed position if greatly dilated.

8) Snout length - from the anteriormost part of the snout or upper lip at the mid-line to the bony front margin of the orbit.

9) Orbit diameter - greatest diameter between the bony rims of the orbit. This distance is not always horizontal.

10) Postorbital length - greatest distance between the posterior bony orbit margin and the bony opercular margin.

11) Interorbital width - least bony width between the orbits over the top of the head in a straight line.

12) Predorsal length - from the base of the anteriormost dorsal fin ray to the tip of the snout or upper lip.

13) Prepelvic length - from the base of the anteriormost pelvic fin ray to the anteriormost point on the head (snout or upper lip).

14) Preanal length - from the base of the anteriormost anal fin ray to the anteriormost point on the head (snout or upper lip).

15) Length of caudal peduncle - the oblique distance from the insertion of the anal fin to the mid-point of the end of the hypural plate.

16) Depth of caudal peduncle - the least depth of this structure from the mid-line of the ventral surface.

17) Length of the longest dorsal and anal fin rays - from the structural base of the ray to its tip.

18) Length of the dorsal and anal fin bases - from the anteriormost ray base (the origin of the fin) to the point where the fin membrane contacts the body behind the last ray (the insertion of the fin).

19) Length of the pectoral and pelvic fins - from the extreme base of the uppermost, outermost or anteriormost ray to the tip of the fin.

20) Distance between pectoral and pelvic fin bases - used principally in Cyprinidae and Cobitidae, this and the following measurement are from the extreme base of the anteriormost, uppermost or outermost ray of the appropriate fin to the anterior base of the next fin.

22) Length of fin spine - from the base of the spine to its tip. In pungent spines, as in catfishes, this excludes soft rays or membranes distal to the sharp tip, but in more flexible spines, which may taper gradually as in Cyprinidae, this measurement includes the soft tip.

mortality = the death of fish; a measure of the rate of death of fish due to such factors as pollution, sickness and starvation but mainly predation (in unexploited stocks) and fishing (in exploited ones).

mortality rate = the rate at which the numbers in a population decrease with time due to various causes. The proportion of the total stock (in numbers) dying each year is the annual mortality rate. To facilitate calculations, mortality is expressed as an exponential rate (called instantaneous rate) thus Nt/N0 = e-Z = e-(M+F) in which Nt/N0 is the survival rate, M the natural mortality rate, F the fishing mortality rate, and Z the total mortality rate (of deaths due to predation or disease).

morphotype = 1) one of several morphologically distinguishable populations of a single taxon.

morphotype = 2) a figured specimen which has not been used to illustrate anything not previously known about the morphology of the taxon.

mort = a young salmon, variously given as in its first or third year, or referring to any young salmonid (British dialect).

mortality pit = an excavation use for the disposal of large numbers of fish specimens contaminated with toxic substances, drugs or diseases and parasites. Hydrated lime can be added to raise the pH to lethal levels, destroying pathogens. The pit may be lined if the fish contain contaminants that would pollute the ground water.

mortality rate = 1) in fisheries the rate at which fish die from fishing and natural causes. Instantaneous rates with short time intervals are used to allow separation of the primary components as instantaneous fishing mortality (F) and instantaneous natural mortality (M). These two equal instantaneous total mortality (Z).

mortality rate = 2) the number of deaths per unit of population over a specified period.

morula = a stage in egg development where the blastomere forms a mulberry-like cluster,

mosaic teeth = the series of rows of flat teeth found in rays and skates, and some sharks, used for crushing such hard foods as molluscs and crustaceans. Also called pavement teeth.

mosquitofish = Gambusia spp. (Poeciliidae) used as a malaria control agent and widely introduced across the world. These fishes eat the aquatic larvae and pupae of malarial mosquitos.

mother ship = a large vessel servicing fishing vessels and on which fishing vessels load their catches for processing and transport to port.

motile aeromonad septicaemia = bacterial haemorrhagic septicaemia (a bacterial infection with Aeromonas liquefaciens, Aeromonas hydrophila or Pseudomonas affecting fishes of all ages, usually in spring. Usually associated with stress and overcrowding. Haemorrhages occur in the skin, fins, mouth cavity and muscles. Exophthalmia and cavity ulcers may occur. Also called infectious dropsy, red pest, freshwater eel disease, pike pest, and redmouth disease.

motor fishing = maintaining station over a fishing spot using the boat's motor. Used in deep water where it is impractical to anchor and/or too time-consuming.

mottled = colouration composed of pigmentation that runs together; blotched; small dark and light areas interspersed.

mousie = 1) a small white worm or grub used as bait in ice fishing. Usually the rat-tailed maggot of the hoverfly, cultured as bait. The rat-tail is a telescopic siphon used as a snorkel for breathing while submerged.

mouth = 1) the structure through which food and water for respiration enter the fish body.

mouth brooder = oral brooder (a fish which broods or protects the eggs (ovophile) or young (larvophile) by taking them into the mouth). This reproductive guild (q.v.) includes those fish that mouth brood without buccal feeding and those that buccal feed the embryos. The former incubate eggs in the buccal cavity of the male, the female or both sexes, the eggs are large, spherical or oval, with dense yolk, are churned in the cavity or are densely packed with well-developed respiratory plexuses aided by endogenous oxidative metabolism of carotenoids, embryos do not feed externally in the buccal cavity, and large young are released, e.g. Apogon imberbis, Oreochromis mossambicus. The latter have fewer and larger eggs and early hatching embryos with a large yolk which feed on particles inhaled by the female, e.g. Arius falcarius, Cyphotilapia frontosa.

mouth fungus = a bacterial infection (Flexibacter columnaris or Flavobacterium columnare)(not a fungus) causing a cotton wool-like growth usually in the mouth region. A rapid infection, often fatal, first seen as light grey marks. Usually occurs in aquaria with pH over 6, higher temperatures and hard water and to fish that are already injured. Proprietary treatments are effective and the antibiotic oxytetracycline can be used for valuable fish. Called columnaris disease when found on other parts of the body. Usually occurs in summer in natural waters and is associated with stress, crowding, injury and poor water quality. Virulent forms may show no external symptoms, less virulent forms show grey-white lesions on the body, fins and gills. Lesions first appear on the caudal fin and progress towards the head. Heavy infections appear yellow or orange. Scaleless fish show lesions comprising a dark blue area overlain by a milky veil and with a red-tinged margin. See also saddleback, saddlepatch disease and mouth rot, depending on locality on body.

moveable ethmoid = kinethmoid (a small median bone in the snout dorsoposterior to the premaxillaries in cyprinoids (between the nostrils). Replaces rostral bone, now restricted to primitive bony fishes. Aids in protrusion of the premaxillaries).

MS (plural MSS) = manuscript (a text, either handwritten or typed, but not available in multiple copies. Used for the copy of a scientific paper submitted to a journal for publication).

MS-222 = a fish anaesthetic applied by immersion in dosed water (tricaine methanesulphonate, methanesulfonate salt or 3-aminobenzoic acid ethyl ester (C₉H₁₁NO₂� CH₄SO₃)). A white powder best transported across borders in its original container.

MSDS = Material Safety Data Sheet (documents form the manufacturer of a chemical outlining its toxicity, volatility, flammability and other safety related information. Posted in laboratories where such chemicals are used; formalin is probably the commonest and most toxic chemical encountered by ichthyologists).

MSP = abbreviation for maximum spawning potential of a fish stock (spawning potential ratio, q.v., or % MSP (the ratio of spawning potential per recruit under a given fishing regime relative to the spawning potential per recruit with no fishing)).

MSST = abbreviation for minimum stock size threshold or B_threshold. At stock sizes below B_threshold, the stock is considered to be overfished.

MSY = maximum sustainable yield (the average or maximum catch that can be removed under existing environmental conditions over an indefinite period without causing the stock to be depleted, assuming that removals and natural mortality are balanced by stable recruitment and growth. Abbreviated also as Y_s. Also called maximum equilibrium catch, maximum sustained yield, sustainable catch).

MT = metric ton (tonne; 1000 kilogrammes, 0.984 long tons, 1.1023 short tons or 2204.6 pounds).

mucin = a product of mucus cells which, when mixed with water, forms mucus. A glycoprotein.

muco-cartilage = a special elastic tissue forming the skeleton of the ammocoete head in Petromyzontiformes. It metamorphoses into true cartilage and other tissues.

mucophagy = feeding on the mucus of fishes or invertebrates, e.g. sabre blennies, Plagiotremus, deliberate or incidental mucophagous cleaners such as Pomacanthidae and Chaetodontidae.

mucosal fold = a fold of tissue lining the intestine; well-developed in some fish larvae giving a characteristic striated or rugose appearance.

mucous canal = an old name for lateral line canal (q.v.) based on the false concept of their function being to produce mucus.

mucous cell = an epidermal cells which secretes mucin, which, when mixed with water forms mucus. Mucous cells are derived from the basal layer of the epidermis and, when mature, communicate with the surface by a lumen. Mucus accumulation may transform the cell into a flask-shaped goblet cell.

mucous tubule = a special kidney tubule which produces a granular slime-like substance in the Gasterosteidae.

mucus = a slimy, clear, slippery fluid formed by the mixture of mucin, a glycoprotein, from the mucous cells and water. The adjective, mucous, may not always be used in conjunction with nouns.

mud = detrital material made of particles smaller than sand, i.e. less than 0.0625 mm in diameter.

mud fish = 1) partially split, salted and pickled cod, caught in autumn and thus too late to cure but kept in salt brine for spring curing. Often kept for home consumption in Newfoundland.

mud fish = 2) any of several species of fish which frequent, or burrow into, mud.

mud taste = an off taste in fish, often found in post-spawning individuals suffering from muscle breakdown and depletion of fat reserves.

mudding = a behaviour of bonefish (Albula vulpes) where they stir up the marl, a greyish-white, soft and adhesive sediment found on the flats where bonefish live.

muddy flavour = a tainted flavour or odour of fish flesh caused by the chemicals geosmin and 2-methylisoborneal released by microorganisms in the water and taken up by fish through their gills. These chemicals have very low detection thresholds, about 1 nanog/l. Found in fresh and brackish water fish as the responsible Cyanobacteria (Anabaena (geosmin) and Oscillatoria (2-methylisoborneal)) do not grow in sea water. Also called earthy flavour.

mudfish = a general term used to describe a wide variety of unrelated fishes that burrow in mud.

mudflat = an area of flat muddy land exposed at low tides and a habitat for fishes such as mudskippers.

muds = a cloud of mud in clear water caused by bottom-feeding fish such as bonefish.

mugil = from the Latin mulgeo, to suck, as in bottom deposits. Hence the name Mugilidae for the mullet family.

M�ller's duct = the duct out of which the oviduct is formed. Also called M�llerian duct.

M�llerian mimicry = the condition where unpalatable species resemble each other, and are recognised and avoided by predators. The chance of being damaged by an uneducated predator is reduced by more than one species having the same appearance.

M�llerian process = a spring-like modified portion of the parapophysis of the 4th vertebrae involved in the elastic spring apparatus, q.v., for sound production.

M�llerian protractor = the muscle inserted on the M�llerian process, originating on the neurocranium in most Siluriformes with the elastic spring apparatus, or on the expaxial musculature near the dorsal fin in Synodontis catfishes. It pulls the process forward, enlarging the gas bladder and, when relaxed it allows the spring-like process to recoil, causing the gas bladder to pulsate and emit sound.

mullet = 2) an unattractive but strangely popular hairstyle, short hair on the top, front and sides of the head, followed by a long drape of hair on the back, reaching at least to the middle of the spine.

mullet millionaire = 1) a nickname for two amateur fish farmers of Roman times who grew red mullet and carp in ponds, species which fetched enormous prices among epicureans.

mullet millionaire = 2) a person who becomes rich through a lottery win or some other type of windfall without hard work or inheritance.

mulm = detritus (dead vegetal matter, faecal pellets and uneaten food forming a greyish gunk on the bottom of aquaria and in filter mechanisms).

multi-day fishing = an allowance (by permit) for a recreational fisherman to possess more than one daily bag limit of fish while on a fishing trip that lasts longer than one day.

multi-monofilament = a small number of monofilament strands twisted loosely together to make up netting for static gear, e.g. tangle nets.

multi-rig bottom trawl = a single vessel tows two or more trawls using outriggers on each side.

multi-strand line = a bundle of very fine fibres comprising a fishing line. The hooklength spreads out in water to become almost invisible and is soft to touch on the lips of fishes. However it may tangle and water soluble glues can be used to keep the strand together until the rig is cast into the water when it dissolves away.

multicellular gland = an innervated group of cells in a round capsule at the end of a jelly-filled tube opening to the skin surface of Gymnarchidae and Mormyridae; electric sense organ. Also called snout organ or mormyromast.

multicuspidate = bearing several points or cusps, as in teeth (more correct form of the above).

multifid = divided into several, having branches or forks, e.g. a spine or the lateral line.

multifurcation = a node in a tree that connects more than three branches. If the tree is rooted or directed, one branch represents the ancestral lineage and the other branches descendent lineages. A multifurcation often results because of a lack of data to resolve the branches although it could be the simultaneous splitting of several lineages. Also called polytomy.

multiple clutch = fractional spawning (release of eggs at intervals, usually over several days or weeks. This allows more, smaller and immature eggs to be carried in a limited abdominal cavity space as the intervals enable the smaller eggs time to mature; and once shed, eggs mature at different times and thus may avoid complete loss of a season's spawning to predators. Also called batch spawner).

multiple oviparity = a system in sharks where females retain several pairs of egg cases in the oviducts, the embryo growing to an advanced stage. The eggs may hatch within a month of laying, e.g. in the scyliorhinid Halaelurus in aquaria, although not known in the wild. May occur naturally in whale sharks.

multiple weight increment = fish yield of a certain species (kg)/stocked quantity of the fish (kg)

multiple zone = a number of closed zones, compared to the size of the calcified structure and the distance of the annuli, which is regarded as one annulus.

multiplier reel = a reel where one turn of the handle causes multiple turns of the spool and so retrieves line rapidly.

multipurpose vessel = a fishing vessel equipped with more than one kind of gear, e.g. seiner-handliner, trawler-drifter, trawler-purse seiner.

multispecies fishery = a fishery where more than one species is caught at the same time. Most fisheries are of this nature as gear is not usually selective for single species but the term is used for fisheries deliberately directed to catching more than one species.

mummy = fish were a staple item in ancient Egyptian diets and were also mummified as representatives of various gods, e.g. Lates niloticus (Latidae) was worshipped as a form of the goddess Neith at Esna, giving rise to the town�s Greek name of Latopolis and Schilbe mystus (Schilbeidae) was the fetish of the delta nome of Mendes, whose local goddess was called Hatmehyt (�foremost of the fishes�) who is usually depicted with a Schilbe on her head. Fish-eating was banned in areas were certain fish species were venerated.

mun = 1) 4 kg or about 9 pounds, used in the Persian Gulf for fish weights in the market.

Munsell system = a commercially manufactured system of colour notation with colour chips enabling naturalists to describe colours of living specimens with some degree of comparative accuracy.

muntle = a line thrown from a boat to a man on the bank. This line is attached to a net that has been payed out from a boat across a river. A Severn River, England salmon-fishing term. See also debut line.

murderer = fluke bar (an iron rod with hooks dragged along the sea floor to impale fish such as flatfishes).

muria = a fish sauce of the ancient world made with tuna in brine allowed to ferment. Fish blood, spices and herbs may be added. See also garum and liquamen.

murmillo = a Roman gladiator with a characteristic crested and broad-rimmed helmet, resembling a fish. Often paired in combat against a retiarius (q.v.) who wielded a net and resembled a fisherman.

Murphy's Law = states, if something can go wrong it will. Also known as Finagle's 2nd law (there are no 1st or 3rd laws).

muscle = fish have three types of muscles, cardiac (only in the heart), smooth (in the viscera, blood vessels or mixed with other tissues), and striated or skeletal (arranged to move the bones). Cardiac muscle has striations, branching fibres and nuclei in the centre of the fibres. Smooth muscle has unstriated fibres, centrally located nuclei and are smaller than striated muscles. Striated muscles has large, longitudinal fibres with cross striations and several, peripherally located nuclei.

museum abbreviation = museum collections of fishes are catalogued with an abbreviation of the museum's name (an acronym) and a number; these acronyms are listed in Leviton et al. (1985) and Leviton and Gibbs (1988), e.g. CMNFI = Canadian Museum of Nature Fish Collection. CMNFI 1979-0102 indicates the 102nd collection (one or more specimens and species) catalogued, but not necessarily collected, in 1979.

mutatis characteribus = with the characters changed (by); emend., emendatus. Abbreviated as mut. char.

mute as a fish = fish lack sound production compared to mammals and birds (slang).

muttsucker = a hybrid composed of two native species of sucker from the Colorado River basin, U.S.A. (flannelmouth and bluehead) with an introduced sucker (white). The white sucker acts as a genetic "bridge" between the two native suckers which do not hybridise. A hybrid swarm may develop and take in other sucker species too.

mutualism = a form of symbiosis in which both species are benefited without injury, e.g. relationship between Amphiprion and certain sea anemones.

mycobacteriosis = tuberculosis (a mycobacterial infection found in aquarium fish, for example (Mycobacterium marinum and M. fortuitum are known causes). Fish are lethargic, show little interest in food, exhibit wasting, hollow bellies, popeyes, colour loss, deformities, ulcers, frayed fins, yellow or dark nodules on the body and eyes, and secondary infections. Some fish, such as salmonids, may show no external symptoms although the disease is fatal from internal lesions. Mycobacteriosis is a zoonose, a disease capable of infecting humans, entering through skin abrasions and causing skin granulomas. Poor aquarium conditions can allow this infection to take hold. Fish can be treated with proprietary medicines for mild cases, by antibiotics but severe cases may be untreatable. The fish tank needs disinfection. Also called fish TB).

myelenocephalon = the posterior part of the hindbrain. Details of the brain structure of a fish (Danio rero) may be found in Wullimann et al. (1996). See also brain.

myocommata = 1) the transverse membrane between the lateral muscle segments of the body; myoseptum.

myodome = 1) a cavity in the skull under the brain in the postorbital region of the skull in which lodge the rectus muscles (anterior, posterior, superior and inferior) of the eye and, anteriorly, the ethmoid for anchoring the oblique muscle (superior and inferior). Actinopterygii typically have well-developed myodomes but some taxa, such as Acipenser, Lepisosteus and Siluridae have lost them.

myodome = 2) a small, subconical, perichondral bone formed in the ethmoid cartilage and making the anterior wall of the myodome.

myoliquefaction = a deterioration and softening of fish tissues caused by Kudoa thrysites, a myosporean parasite in marine fishes. This results in economic loss but the parasite does not infect humans.

myomere = a lateral, W-shaped muscle segment of the body, separated from its neighbours by fibrous connective tissue. The upper central point of the "W" is directed anteriorly. Superficial fibres are separated from deeper ones, the former being red muscle or musculus lateralis superficialis with smaller fibres and more blood vessels, and the latter white muscle or musculus lateralis profundus. The two layers are separated by a septum of fibrous connective tissue. Red muscle is thickest at the lateral line, thinning dorsally and ventrally. Myomeres attach to the myocommata and thus indirectly to the vertebrae. Some are supported by neural and haemal spines. These myomeres are the muscles used in movement.

myomere count = in lampreys the myomeres between the 7th gill (first counted is that whose posterior septum passes entirely behind the groove) and the one whose lower posterior angle lies wholly or partly above the cloacal slit. Sometimes myomeres are counted between the eye and the cloaca, although this count seems to have little to recommend it.

myomere formula = preanal plus postanal myomeres equals total myomeres in larval fishes.

myorhabdoi = slender bones projecting backwards and downwards in the myocomma from each neural spine.

myoseptum (plural myosepta) = the partitioning tissue between the muscle blocks; myocommata.

myxobacteriosis = a disease of fish caused by any member of the Myxobacteria, .e.g. coldwater disease, columnaris disease, fin rot, peduncle disease, etc.

myxopterygium (plural myxopterygia) = the copulatory organ or clasper of Elasmobranchii and Holocephali; rod-like extensions of the inner side of the pelvic fins. It is composed of the long stem cartilage, a shorter distal cartilage, the dorsal terminal cartilage (or rhipidion, fan-shaped for dispersing sperm in a radiating spray during copulation), the hook-shaped terminal cartilage (or claw) which has a cutting edge on its inner margin, and the narrow, sharp spur. The claw and spur serve to anchor the clasper in the female oviduct and a groove along the clasper enables the sperm to reach the oviduct. The siphon contracts to propel sperm into the oviduct. See also tenaculum.

myxosomiasis = whirling disease in salmonids caused by Myxosoma cerebralis or by other Myxosoma spp.

myxosporidiosis = a disease of fishes caused by the sporozoan protozoan Myxosporidium.

Nov	DEC	Jan
	06
2008	2009	2010