Dictionary of Ichthyology
Brian W. Coad and Don E. McAllister†
Z
Z = total mortality rate (the number of fish which die during a year or season, divided by the initial number. Also called actual mortality rate, coefficient of mortality. Instantaneous rate of mortality (the natural logarithm (with sign changed) of the survival rate. The ratio of number of deaths per unit of time to population abundance during that time, if all deceased fish were to be immediately replaced so that population does not change (Ricker, 1975). Also called coefficient of decrease).
z = instantaneous rate of recruitment (number of fish that grow to catchable size per short interval of time, divided by the number of catchable fish already present at that time. Usually given on a yearly basis, i.e. the figure just described is divided by the fraction of a year represented by the short interval in question. This concept is used principally when the size of the vulnerable stock is not changing or is changing only slowly, since among fishes recruitment is not usually associated with stock size in the direct way in which mortality and growth are (Ricker, 1975)).
Z' = disappearance (the rate of decline in numbers of fish caught as fish become less numerous or less available. Often calculated from catch curves).
zavinac = rolled up pickled herring, the term used for the @ sign in email addresses in Slovakia and the Czech Republic.
zebec = xebec (a small, three-masted vessel used by Mediterranean pirates and still used in commerce to a limited extent. From the Arabic shabbak. Also spelled chebec).
zebrafish = Danio rerio (formerly Brachydanio rerio), a member of the Cyprinidae used to study vertebrate biology, physiology, genetics, developmental biology, neurology and human disease. It has a short generation time, is highly fecund, fry are transparent, and many mutants with features resembling human diseases have been identified.
zentner = centner (50 kg).
zeolite = an ammonia-removing, ion-exchange resin used in freshwater aquaria. It also can act biologically and mechanically. Does not last long and must be regenerated by soaking in a strong salt solution for a day. Particularly useful for temporary ammonia problems, in hospital tanks where the chemicals are harmful to biological filters and in transporting fish on long journeys.
zhirovaya = watery or mushy caviar taken from sturgeons before they are ready to spawn.
zig rig = in angling, a rig used for presenting floaters, q.v., which rise up from a bottom weight.
zigzagging = using a boat in a controlled fashion to troll a lure in a weaving pattern, imparting an erratic action to the lure to avoid spooking shallow fish. Also called snake trolling.
zipper = 1) the opening edge along the upper forward seam of the cod end of a mid-water trawl facilitating removal of fish.
zipper = 2) a structure for lifting the leadline of a purse net to the surface in order to divide a large catch or to isolate a small catch.
zipper = 3) an item of dress often found open in drowned male anglers fishing from a small, unstable boat.
zipper worm = in angling, a plastic worm with a flat but ridged body (like a clothes zipper).
zipperlip = angling slang for a secret fishing hole.
Zmbp or ZMBP = abbreviaton for level of total mortality at which the maximum biological production is obtained from the stock.
Zoll = 26.15 mm in Germany; the Wiener Zoll = 26.34 mm in Austria. Both may be used in older taxonomic works.
zona radiata = a thickened, rather complex egg membrane of teleost fishes, which often has a radiate appearance. It is formed at the surface of the egg by the ooplasm, or the ooplasm and the follicle cells and hence should be regarded as a true vitelline membrane. May be overlain by the chorion, q.v. In Elasmobranchii the zona radiata underlies or overlies a homogeneous vitelline egg membrane.
zonation = a distinct animal and plant community. Often refers to zonation on a sea shore where fishes, for example, are found at different levels of tidal influence and associated with different plant communities.
zone = 1) a region of similar structure or optical density laid down during growth of hard parts used in ageing. Also called band, mark and ring although zone is preferred.
zone = 2) a fishing zone is a zone of variable width (up to 200-nautical-miles) proclaimed by a coastal State around its coast, within which it controls domestic and foreign access to fish resources.
zone = 3) an area of rocky shore, reef flat, mangrove swamp, etc. that has distinct animals and plants.
zonolimnetic = pertaining to a particular depth zone in a lake
zoobenthivore = feeding on zoobenthos.
zoobenthos = animals living on or in the bottom of the sea or fresh waters.
Zoug jar = Zouger jar.
Zouger jar = a bottle for the incubation of fish eggs with water flow upward to maintain eggs in suspension for adequate oxygenation. The outlet may have a fine meshed grid to prevent loss of larvae. Also called Zoug jar.
zoological formulae = modifications of available names throughout a taxonomic group by the addition of a standard prefix or suffix in order to indicate that the taxa named are members of that group. Zoological formulae are excluded from the provisions of the International Code of Zoological Nomenclature. The suffixes of family-group names denote ranks, not taxonomic groups, and do not form zoological formulae.
zoological name = the scientific name of an animal taxon in binominal nomenclature.
zoological nomenclature = the system of scientific names for animal taxa and the provisions for the formation, treatment, and use of those names.
zoological taxon = a natural taxon of animals, named or unnamed.
zooneuston = the animal component of the neuston.
zooneustont = an animal of the neuston.
zoonosis = an infectious disease of animals, including fishes, that can be transmitted to humans, e.g. fishkeeper's granuloma or fishtank granuloma, an infection in humans with the bacteria causing fish tuberculosis (a Mycobacterium, but not the same as the one causing human tuberculosis). It is probably the only zoonosis of note to aquarists. It appears as a skin infection, usually on the hands or forearms where there was an earlier cut, and may be inflamed, suppurating, encrusting and irritated. Not usually serious unless the infected individual is already immunosuppressed. Treatment requires antibiotics.
zoophagus = eating animals or animal matter.
zoophagy = feeding on plankton and benthos, relatively small animals.
zooplankter = an animal of the plankton.
zooplankton = animal plankton.
zooplanktont = an animal of the plankton.
zulu = 1) an artificial fly used on lakes on dark days in Britain; for trout and sea trout.
zulu = 2) a type of fishing-boat common on the Moray and Clyde Firths, Scotland, in the late nineteenth century with fore- and mizzen-masts, a straight prow and a markedly raked stern. Some models were later fitted with engines.
zulu skiff = a smaller type of zulu, generally with only one mast.
zygapophysis = articular process that extends forward and backward of neural arches and help to strengthen the union between vertebrae.
zygote = the fertilised egg.
© Brian W. Coad (www.briancoad.com)