Dictionary of Ichthyology
Brian W. Coad and Don E. McAllister†
U
ubiquitous = having a worldwide distribution, common to abundant in a given area.
UDN = ulcerative dermal necrosis ( a disease affecting salmonids returning from the sea to fresh water with head lesions. The cause is probably viral but the lesions are typically infected by bacteria and fungi).
ug = the pectoral fin of a fish and its adjacent parts (Caithness dialect). Also spelled ugg.
ugg = ug.
ugg bone = the bone(s) behind the gills of a fish (the pectoral complex), the main bone being the cleithrum) (Scottish dialect).
ulcer disease = a subacute to chronic systemic bacterial disease of salmonids caused by Hemophilus piscium.
ulcerative dermal necrosis = a disease affecting salmonids returning from the sea to fresh water with head lesions. The cause is probably viral but the lesions are typically infected by bacteria and fungi. Abbreviated as UDN.
ulcerative disease of goldfish = furunculosis (a systemic bacterial disease (Aeromonas salmonicida) generally of salmonids but also found in some flatfishes such as turbot (Scophthalmus maximus) and in goldfish. Usually occurs in young fish following stress and in spring when temperatures rise and is characterised by loss of appetite as the intestine is inflamed. Septicaemia and haemorrhages in the muscles and other areas occurs. Furuncules (boil-like lesions) develop in body tissues).
ultimate = last or farthest, e.g. ultimate ray.
ultimate lifeform = ray-finned fishes (Actinopterygii) (Morrison, 2007).
ultimate vertebra = terminal vertebrae (the last complete centrum of the vertebral column; not homologous across taxa because of varying fusions of preural and ural centra and so of little utility).
ultimobranchial gland = a paired endocrine gland producing calcitron which helps regulate the calcium level by lowering it. Located between the ventral wall of the oesophagus and the sinus venosus. See also corpuscles of Stannius.
ultra- (prefix) = beyond.
ultra-abyssal zone = hadal zone, q.v.
ultra-light = a very flexible, thin fishing rod used with light lines (2-6 lbs) and small lures. Used for crappie and trout.
ultrahaline = sea water with a salinity greater than 30 parts per thousand.
ultraoligotrohic = an aquatic ecosystem having an extremely low nutrient supply and productivity.
ultraviolet steriliser = an aquarium device that sterilises water by passing it through a glass tube around an ultraviolet light. Useful in removing bacteria, algal spores and parasites.
umbrella net = a lift net, q.v., in the shape of an umbrella.
umbrella species = a species whose protection will also protect a wide range of co-existing species in the same habitat, which may be lesser known and difficult to protect otherwise.
unadon = literally "eel bowl" in Japanese, a rice dish with grilled eel coated in a sweet sauce.
unagi maki = eel roll as served in a sushi restaurant.
unagi no kimo = eel innards as served in a sushi restaurant.
unavailable = used of a name, nomenclatural act or work that does not comply with the provisions of the International Code of Zoological Nomenclature, or that has been annulled by the Code.
unavailable name = a name which does not meet all mandatory provisions of the International Code of Zoological Nomenclature. Has no status in nomenclature. Unavailable names include nomen oblitum, nomen negatum, nomen nudum, nomen nullum, nomen vetitum (all q.v.).
unavailable work = a work published prior to the starting point of the group, or one that does not conform to the provisions of the International Code of Zoological Nomenclature or that has been annulled by the Code.
unblocked quota = fishing shares that can be subdivided when transferred, although there are limits on the number of these shares that an individual may own.
unbusked = an undressed hook in fly fishing.
uncertainty = the difficulty in obtaining complete and accurate knowledge of all the factors affecting a stock assessment, in compiling biological data and in the management of a fishery. Uncertainties include measurement errors, natural population variability, e.g. in recruitment, error in use of models, estimation errors, and management implementation errors.
uncinate = hooked at the tip.
unculi = plural of unculus.
unculus (plural unculi) = a horny projection arising from a single cell of the epidermis, unlike the multicellular, horny breeding tubercles; found in Chanidae, Cyprinidae, Balitoridae, Sisoridae, e.g. on the disc of Garra and over much of the body surface in some Sisoridae. Function is possibly adhesive, protection of the skin, rasping and hydrodynamic.
unculiferous = bearing unculi.
under-gravel filter = an aquarium filter providing both mechanical and biological filtration. It consists of a perforated plate placed on the bottom of the aquarium and then covered in gravel. Water is pulled through the gravel, under the plate, and up through lift tubes.
under-reporting = failing to fully report all the fish caught and landed.
under-running = the process of hauling in a net over the bow of the boat and, e.g. with a longline, removing fish, and re-baiting and re-setting the line. When this was done by fishermen from a dory, a 1.5 km line was set, with a fish caught every tenth to fifteenth hook, and the line was pulled and set three or four times a day.
under-running stick = a piece of wood that kept the line and hooks from snagging the dory when under-running.
undercut = said of river banks where erosion leaves a section of bank overhanging the water. Some undercut banks are fairly stable when held together by vegetation (roots) and provide a sheltered habitat for fish, others collapse and may silt up spawning sites.
underfished = a stock which could sustain catches higher than current ones; there is high survival of juveniles and moderate to severe competition for resources among adults.
undergravel filter = a form of aquarium filter consisting of a perforated plate placed under the gravel on the bottom of the aquarium. The plate has several uplift tubes terminating at or near the water surface. The substrate acts as the filter bed as water is drawn down through it, into the plate and up the tubes. A reverse flow system also works where the water rises through the substrate. The filter bed should be 6.0-7.5 cm deep and the grain size should be 4-5 mm for efficient filtering.
undershot = underslung.
undersized = fish caught at a size smaller than the minimum size limit established by regulation.
underslung = subterminal mouth or jaw.
understocking = a pond stocked with a number of fish less than its capacity.
underutilised = a species or stock that has potential for a large additional harvest.
underwater farming = aquaculture (the artificial or controlled culture of aquatic organisms, including stripping and fertilisation of eggs and raising of young to a certain size for release or marketing).
underyearling = a fish less than one year of age.
undeveloped = a fishery in its very early stage of development, with very low levels of fishing effort, producing much lower quantities of fish than its potential maximum yield.
undressed jig = a bare jig hook with a molded lead head used with live bait.
undulate = having a wavy margin.
undulating = moving in waves, e.g. fish swimming; movement of the female fish's in a waving motion used to move gravel for the construction of a redd.
undulatory swimming = muscular undulations passing along the body, generating forward movement. See also oscillatory swimming.
unfed fry = fry from the time the yolk-sac is absorbed until it starts feeding.
unfished = a fish or population of fishes not fished for.
unfished ground = an area where fish catches are not carried out.
unfiskalee = not suited to fishing (Scottish dialect).
ungutted = fish prepared for sale as food without the guts removed.
unhooking mat = a thick, soft, sometimes inflatable mat, wetted with water, and used by anglers to place a fish on while unhooking it. Such a mat preserves the mucus covering of the fish and allows it to be returned alive to the water with a better chance of survival.
uni- (prefix) = one, single.
uni knot = a knot used by anglers to connect hooks, swivels, rings and lures. Various websites have animated steps showing how to tie this knot. Also called Duncan loop.
uni-to-uni knot = a knot used in angling to tie two pieces of line together. Useful in tying monofilament to braided line as the latter tends to cut the former. Various websites have animated steps showing how to tie this knot.
unicaniculate = having a single canal or groove.
unicuspid = with a single point cusp, e.g. unicuspid tooth.
uniformitarianism = the present is the key to the past. The physical and biological factors which link today's variations must have been in operation in the past. Also called Principle of Continuity.
uninomen = a scientific name consisting of a single word, used for higher taxa above the rank of genus.
uninominal = the adjective for uninomen.
uniserial = arranged in a single row or series.
unisexual fish = one-sexed; an all-female "species". These fishes are of interspecific hybrid origin, have clonal inheritance and often include polyploids, e.g. Poecilia formosa. See also biotype, bisexual, gynogenesis, hybridogenesis, parthenogenesis.
unit = a fishing unit is the gear, processes and people that together can fish autonomously.
unit stock = a population of fish, either of one or a number of species, grouped together for assessment purposes which may or may not include all the fish in a stock. The fish occupy a particular area and live independently of other populations of the species; an arbitrary grouping of populations large enough to be self-reproducing and showing similar patterns of growth, migration and dispersal.
unite = in taxonomy, to combine or join two or more taxa.
Universal Transverse Mercator = a system for indicating locations on the Earth's surface based on ground distances. Locations are designated in terms of distances in metres east of the centre of a UTM zone and north (or south) of the equator. The earth is divided into sixty zones, each 6 degrees of longitude wide. Each zone is projected onto a Transverse Mercator projection. UTM zone 1 extends from 180° to 174°W. Each zone extends from 80°S latitude to 84°N. Abbreviated as UTM.
universal trawl = multipurpose trawl, one that can be used for midwater and bottom trawling.
univoltine = one generation per year or season.
unjustified emendation = any emendation other than a justified emendation (the emended name is treated as a new name with its own authority and date).
unknown stock = stocks where there is insufficient information to identify stock origin or stock status with confidence.
unmade = split and salted cod, but not dried (Newfoundland).
unpublished name = a type to be conserved; any name which has not been printed and circulated to meet the criteria of publication as stated by the International Code of Zoological Nomenclature.
unregulated fishery = a fishery in which producers and others involved are not subjected to any regulations.
unscheduled record = a museum record for which final deposition has not been determined.
unsegmented ray = a soft ray, usually small, without segments and found at the beginning of a fin.
unused name = an available senior synonym that is not known to have been used as a valid name in the past 50 years.
upland = hilly terrain with a stream type of moderate gradient and with runs and riffles 10-50% of the length.
upper jaw length = the distance from the anterior tip of the upper jaw to the posterior tip of the upper jaw. Sometimes miscalled maxillary length when the premaxilla enters into the upper jaw.
upper limb = the vertical portion of the gill arch.
upstream = towards the source or upper part of a stream or a current; against the current.
upwelling = an upward movement of cold, nutrient-rich water from the ocean depths, often associated with great production of fish and fisheries. For fisheries, the most important types are wind-induced coastal upwelling where the upward movement is a consequence of wind stress (along shore) and Eckman transport (offshore).
unspawned = any mature fish that has not spawned.
uo-miso = a fermented fish paste, made from boiled, dried white meat of cod and kneaded, mixed with soybean paste (miso), sugar, sweet rice liquor and starch. Often sold canned (Japan).
upland catchment water = water from land above about 100-200 m; often unpolluted as higher reaches of river basins are remote from cities.
upmouth = 1) a fishing device on the River Wye in Herefordshire recorded in 15th century manorial records. Probably a basket eel trap with the opening facing upstream to catch adult eels as they migrate towards the sea in late August to early October.
upmouth = 2) a superior mouth; sometimes used in fish names, e.g. upmouth hugo, Hygophum taaningi, a myctophid.
upper limb = the upper part of a gill arch above the bend.
upper pond = the head pond in a series of linked ponds, thus the first supplied with water.
upper reach = trout zone (an area of river with fast currents, a stony bottom, and a fish fauna having cylindrical bodies).
upper river = upper reach.
upper-level consumer = a fish that eats predatory animals; often a piscivore in fishes.
uprush = run-up (the rush of water up a structure such as a beach on the breaking of a wave. Also called swash).
upstream = toward the source or upper part of a stream or current; against the current.
upward cast = a fly fishing cast above eye level used for distance.
upwelling = the movement of nutrient rich waters and colder from the bottom of the ocean to the surface; often results in areas rich in fishes.
ural centrum = the central body of the vertebrae which carry hypurals, after the bifurcation of the caudal artery.
ural vertebra = one of the vertebrae to which hypural bones are attached.
urban fishing = angling near a highway bridge or other non-natural structure.
urceolate = shaped like an urn.
urea = (CH2)2CO, a waste product of metabolism excreted via the kidneys but also found in Elasmobranchii blood to maintain osmotic balance. It is degraded to ammonia by enzymes leading to a characteristic pungent odour in spoiled Elasmobranchii.
uremic = of or involving excess nitrogenous waste products in the urine, e.g. the embryo in Chondrichthyes is four to five times as uremic as the parent since the egg shell is permeable to urea.
ureotelic = producing urea as the main nitrogenous waste, as in fish.
urinary bladder = a small vesicle at the posteriormost, ventral part of the body cavity. In females the bladder is combined with the oviducts to form a urogenital sinus.
urinary calcinosis = urolithiasis.
urinary papilla = the external projection of the male urinary bladder.
urinary pore = the point of exit of wastes from the male urinary papilla.
uriniparous tubule = a urine-producing tubule of the kidney (as compared with the special mucoparous tubules of Gasterosteidae).
urli = a conical-shaped, bamboo fish trap used in rivers to catch fry and fingerlings of mahseer (Cyprinidae) in India.
urodermal = paired, thin dermal bones at the rear of the caudal fin skeleton, derived from scales.
urogenital papilla = genital papilla (a small fleshy projection behind the anus, through which the genital and sometimes urogenital system communicates with the exterior).
urogenital pore = the point of exit of wastes from the female.
urogenital region = the area of the abdomen near the urinary and genital openings.
urogenital sinus = the bladder combined with the oviducts in females.
urohyal = a flat, median, deep, endochondral bone below the ceratohyal; a tendon bone arising in the septum between the longitudinal muscles of the isthmus. Absent in such primitive fishes as Lepisosteus. Also called clidost, episternal, interclavicle and parahyoid.
urolithiasis = the formation of calculi in the urinary ducts.
uroneural = one of the paired, elongate, endochondral bones projecting from the lateral surfaces of the urostyle.
urophore = the caudal skeleton. It is formed from various bones of cartilaginous or dermal origins.
urophysis = a neurosecretory organ at the ventral side of the distal end of the spinal cord, composed of unmyelinated axons ending on the capillary wall. Function unknown.
uropterygia = plural of uropterygium.
uropterygium (plural uropterygia) = caudal fin (the tail fin, aiding movement. The fin at the posterior end of the vertebral column (but in Centriscidae the hind end of the body rotates so that the caudal fin is ventral, and in some Trachipteridae the upper lobe of the caudal may be dorsal (the separate lower lobe may disappear). In other families, such as the Zoarcidae and Anguillidae, dorsal, caudal and anal fins are united and are externally indistinguishable. Abbreviated as C).
urosome = the portion of the body posterior to the vent.
urostyle = 1) the small upturned posterior tip of the vertebral column, generally formed of a slender, pointed rod of cartilage, or fused vertebrae and associated elements (in homocercal caudal fins of Teleostomi).
urostyle = 2) the fan-like series of bones articulating with the last true vertebra, including preural centra, ural centra, epurals and hypurals. Counted as one vertebra in some vertebral counts, not counted in others.
urostyli = plural of urostylus.
urostylus (plural urostyli) = urostyle.
usable stock = the number or weight of all fish in a stock that lie within the range of sizes customarily considered usable or so designated by law (Ricker, 1975). Also called standing crop.
usage = the sense in which a name has been applied, correctly or not according to the International Code of Zoological Nomenclature.
usage, prevailing = that usage of the name which is adopted by at least a substantial majority of the most recent authors concerned with the relevant taxon, irrespective of how long ago their work was published.
use rights = rights for the use of resources that can be defined by local custom, mutual agreements, or prescribed by other entities holding access rights. These rights may restrict the use of particular resources to specific levels of consumption or particular harvesting techniques.
user = a commercial, recreational or indigenous fisher, a fish watcher or scuba diver, or any member of a community with interests in fishes, presumably including ichthyologists.
user group = a group of individuals that utilise a resource in a specific manner.
user participation = resource users playing an active role in the process of fisheries management.
ussel = the short cords in a herring net that attach it to the balk (Northumberland dialect).
utaka = a group of haplochromine Cichlidae in Lake Malawi. This cluster of species feeds in open water, and the individuals are usually elongate and silvery.
uterine cannibalism = the condition in some sharks where the embryos feed on eggs and smaller siblings inside the mother.
uterine milk = histotrophe (or ovarian milk, a secretion produced by teleost livebearers for absorptive feeding during fish ontogeny).
uterus = the organ where fertilised eggs develop. A true uterus is not present in fishes but the term may be used for the egg capsule in Chondrichthyes.
uthy = oothy (a smooth surface made on the sea by throwing out crushed limpets or mussels as inshore bait for coalfish (Pollachius, Gadidae) (Orkney dialect)).
utilised population = utilised stock.
utilised stock = the part, by number, of the fish alive at a given time, which will be caught in the future (Ricker, 1975). Abbreviated as V.
utricle = utriculus.
utriculi = plural of utriculus.
utriculith = lapillus (plural lapilli)(the otolith in the utriculus. It is held in a vertical position against the cells of the utricular macula which is innervated by the anterior branch of cranial nerve VIII (the stato-acoustic nerve). Movements of the lapillus send signals to the brain and help the fish to maintain equilibrium. It is usually very small but is the largest otolith in Siluridae).
utriculus (plural utriculi) = the uppermost sac of the inner ear into which the semicircular canals enter. Contains the lapillus or utriculith otolith, usually the smallest, in Teleostei and minute particles of calcium carbonate called otoconia in endolymph in Elasmobranchii. Also called utricle.
utsuri = ornamental carp or koi (q.v.), being black koi with a single coloured marking.
uvula = the lobate extension of the inner crown base of a chondrichthyan tooth (Herman et al., 1994).
© Brian W. Coad (www.briancoad.com)