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Conversions and Glossary



Celsius to Fahrenheit °F= (°C x 1.8) + 32,

Fahrenheit to Celsius °C= (°F-32) / 1.8

25.4 mm
2.54 cm
76.2 mm
7.62 cm
152.4 mm
15.24 cm
304.8 mm
30.48 cm
609.6 mm
60.96 cm
1000 mm
100 cm
1 inch
3 inches
6 inches
1 foot
2 feet
3.28 feet

FL-fork length: the distance from the tip of the snout or lower jaw to the middle of the fork of the caudal fin (whichever juts out further)

SL-standard length: the distance from the tip of the snout or lower jaw to the end of the vertebral column

TL-total length: the distance from the tip of the snout or lower jaw to the end of the longest ray or longest point formed when the lobes of the caudal fin are brought together



Alevin- a larval salmonid that still has an attached yolk sac full of nutrients

Ammocoetes- larval lampreys

Amphipods- a large group of crustaceans, most of which are small and compressed (e.g. freshwater shrimp)

Anadromous -a life history in which fish hatch in freshwater, migrate or move to an estuarine or marine environment, and then return to freshwater to spawn. Ex. salmon, steelhead, eulachon


Basibranchial teeth - teeth found between the gills and behind the tongue on the basibranchial bone
Benthic - living or dwelling on, at, or in the bottom of the water column or water body
Brachiostegals - bones supporting the gill membranes
Brackish water - water consisting of a mix between fresh and saltwater (estuary), salt or freshwater that has been compromised by the introduction of the other


Caddisflies - insects with various life stages both in and out of water
Centrarchids -members of the family centrarchidae, which includes bass, sunfish, and Sacramento perch
Chironomid - a kind of insect common in a fish’s diet, common examples include gnats, blood worms, midges (Family Chironomidae)
Chromatophores - pigment-bearing cells, frequently capable of expansions and contractions which change their size, shape and color.
Circuli - concentric rings found on bones or scales
Cladocerans - tiny aquatic crustaceans commonly known as water fleas, they can be benthic or planktonic
Copepods - small crustaceans that live as free-swimming or parasitic organisms
Ctenoid - scales with spines on the posterior or exposed portion
Cycloid - Smooth, flat, round scales


Deciduous - scales that easily shed or rub off as a fish grows
Decurved (lateral line) - slightly bent or rounded
Detritus - decomposing organic or inorganic matter (decomposing plants, animals, etc.) usually taken in reference to organic matter
Diatoms -unicellular algae with silica shells, known to cause glittering or sparkling in water
DO-dissolved oxygen - the amount of oxygen dissolved in water, typically measured as mg/L, ppm, or percent saturation
Diurnal - pertaining to daylight hours
Dorsal - the upper or back side of a fish


EC - a measure of a solutions ability to conduct an electrical current
Elements - rays or spines in a fin
Epi-pelagic - associated with the surface of an open water body or water column
Estuary - a transition zone where freshwater and saltwater meet
Euphausids - small pelagic crustaceans
Euryhaline marine species - ocean oriented fish that visit or enter freshwater streams. Juvenile fish are more frequently found in freshwater, though freshwater is not essential to any stage of these species life history
Eutrophic - (water body)characterized by high productivity due to the abundance of nutrients such as nitrogen and phosphorus


Fecundity - reproductive capacity of an organism, i.e. the number of eggs a female fish produces in a reproductive cycle
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 spawning.*
Fontanel - a gap between bones in the skull, bridged by a membrane
Fry - a young fish at the post-larval stage. May include all fish stages from hatching to fingerling. An advanced fry is any young fish from the start of exogenous feeding after the yolk is absorbed while a sac fry is from hatching to yolk sac absorption. In Salmonidae the stage from end of dependence on the yolk sac as the primary source of nutrition to dispersal from the redd.*
Fusiform (body) - tapered and sleek



Heterocercal tail - a caudal fin with two lobes of unequal size


Intermittent streams - streams that only flow for part of the year
Interstitial - between parts or particles (gravel, cobble, etc.)
Interspecific competition - competition for resources, usually prey items, between different species
Intraspecific competition - competition for resources, usually prey items, between members of the same species



Keel- a hardened ridge on the posterior of the body similair to the bottom of a boat; typically found on swift-swimming fishes

Krill - a type of shrimp-like marine invertebrate common in many species diet


Lampreys - eel like aquatic invertebrates that lack jaws or paired fins,
Larvaeceans - small, planktonic, invertebrate animals; commonly found in surface waters
Lateral line scales - the scales that run from the operculum to the base of a fish’s tail. When the lateral line is not present but scales are, a lateral line series count is done. When the lateral line is evident but the fish lacks scales, lateral pores may be counted.
Limnetic - pertaining to or of a lake


Maxilla - one of the two bones that make up each side of the upper jaw
Mayflies - insects with various life stages both in and out of water
mg/L - milligrams per Liter, weight measurement of an element or solute dissolved into a Liter of liquid.   For water mg/L = ppm
Milt - the male sex product or seminal fluid that includes sperm
Minnows - members of the family cyprinidae.
Mottling - markings of spots or blotches of different color or shades of color
Myomeres - muscle segments separated by layers of connective tissue


Nest - the rock, hole, or depression where eggs are deposited


Oblique - situated in a slanted position
Ocellus - a marking in which a ring of one color surrounds a spot of another, the mark resembles an eye and can be effective in confusing predators
Ostracods - tiny crustaceans characterized by a protective carapace


Palatine teeth - teeth located on the palatine bones which are situated inside the upper jaw bone
Papillae - small fleshy projections
Parr marks - dark blotches or large lateral marks found on the sides of young almonds (sometimes on adults)
Pelagic - living or dwelling in the open part of the water column or water body, associated with shallow to moderate depths
ppm - parts per million, a measure of concentration; for water 1 ppm means 1 part of something per 1 million parts water ex.
10 ppm Na+ = 10g Na+ / 1,000,000 g water. 1 gram water= 1 ml. water = 1 cubic centimeter water
ppt - parts per thousand, a measurement of concentration typically used to express the salinity of water, Ex. The ocean has 35 parts salt per 1000 parts of water.
pH - the measure of hydrogen ion activity, measured on a scale from 0 (acidic) to 14 (basic or alkaline); 7 is neutral
Plankton - organisms that passively float or weakly swim in a body of water
Planktonic - a state or form of passively floating or weakly swimming in a body of water
Pool tail - the downstream end of a topographic depression within the stream, commonly where a pool makes a transition to gravel bar or riffle
Pteropods - planktonic mollusks capable of slow swimming movements



Redd - the area consisting of nests or depressions created for deposition and fertilization of eggs during spawning
Reticulated - divided into a network or pattern
Riffle - a turbulent section of fastwater, typically in low gradient alluvial channels. Substrate size tends to be finer than substrate in more turbulent form of fastwater
Riparian - refers to the zone adjacent to a stream, the riparian zone helps provide integral habitat both within and outside water
Rotifers - microscopic aquatic animals


Salmonids - members of the family salmonidae, such as trout, salmon, and mountain whitefish
School - a group of fish, usually of the same species, that move and orient themselves as a unit
Scutes - large bony plates that provide protection to fish (sturgeon) lacking scales
Sexual dimorphism - a distinctly different physical appearance of males and females of the same species
Shoal - an aggregation or school of fish, typically in reference to groups in shallow water
Spiracle - a respiratory opening connected to the gill cavity that is located between the eye and gill slit (found in sturgeon)
Smoltification - the process by which parr transform into smolts, this includes changes in osmoregulation and the ability to enter sea-water.
Stream order - classification of stream or rivers based upon the number of tributaries and confluences: (2) 1st order streams =2nd order stream, (2) 2nd order streams make a 3rd order stream, a 2nd order + 3rd order = 3rd order stream
Suckers/catostomids - members of the family catostomidae, typified by a sub-terminal mouth (found on the underside)


Terminal - located at the very end of something, i.e., a fish’s mouth on the extreme anterior tip of the body
TDS - total dissolved solids: amount of metals, minerals, solids, salts, cations, and anions in water. Dissolved solids can have a significant effect on water quality. TDS is quantified by measuring electrical conductivity (EC) or by evaporating all water to leave remaining solids.
Tubercles - temporary outer projections or nodes found on adult fish during breeding seasons
Turbidity - a measure of light transmission through water with respect to matter suspended in the water. Turbidity is commonly used in measuring water quality


Urogenital papillae - a small conical tube located just ahead of the anal fin and usually visible only during, or shortly before, spawning, through which gametes are expelled.*


Ventral - refers to the underside or belly of a fish
Vermiculations - a pattern of wavy lines or streaks of color; worm-like lines


Yolk sack - a b ag-like ventral extension of the gut containing nutritive materials that first appears in the fish embryo and is later absorbed by the larva during the stage after hatching and before feeding.*


Zooplankton - (small) animals that passively float or weakly swim in a body of water
Definitions with a * designation are taken directly from the FishBase glossary. For a more complete list of fish terms please visit their website at http://www.fishbase.org/search.php