adipose fin: A small fatty fin found on the top back of salmon and trout between the dorsal fin and the tail (caudal fin). This fin is removed (clipped) from Washington state hatchery chinook, coho and steelhead to distinguish hatchery fish from wild fish.
aerate: Supplying with oxygen; with water it is a process of exposing water to the air, usually by churning or breaking the surface of the water, such as waterfalls, riffles, etc..
alevin: Newly hatched fish with yolk sac attached. See sac fry.
algae: Simple plants that grow in water. They range from microscopic size to plant hundreds of feet long.
anadromous: Migratory. A fish that spawns in fresh water then migrates to the ocean, returning to fresh water as an adult to spawn. (From the Greek words for “up river”)
anal fin: Fin located on the bottom and near the back of the fish.
bar: The area at the mouth of a river where sediments are deposited.
brood fish/brood stock: Fish held in the hatchery to produce eggs like one would raise chickens for eggs.
buck: A male fish.
carbon dioxide: A gas (like oxygen is a gas) which is exhaled from animals and absorbed by plants.
carrying capacity: The number of fish or wildlife that can be supported by a given area of land or water.
caudal fin: Another name for the tail of a fish.
char: A genus of small-scaled trout (Salvelinus).
counter-shaded: Offset coloration allowing an animal to hide in its environment. Fish usually have darker tops and lighter bottoms, making it difficult to see them from above or below.
dorsal fin: Dorsal means top. This is the large fin on the top of a fish’s back.
eddy: A current of water (also could be air) which runs against the main current.
electromagnetic signals: Small electrical charges based on magnetic properties.
Endangered Species Act: A law that requires special protection for plant and animal populations that are in danger of becoming extinct.
estuary: The area where the tides of the ocean meet a river current.
eyed egg: A fish egg that has developed to the point where the dark eyes of the embryo can be seen through the shell.
fingerling: A small fish, up to one year of age. A small fish about the size of your little finger. A stage or size measurement in the growth of a fish.
forb: A herbaceous plant other than grass growing on a field or meadow.
freshets: A stream created by overflow or runoff.
fry: Recently hatched fish, after yolk sac has been absorbed, and prior to the fingerling stage.
fungus: A type of lower plant (such as mold) that helps decompose organic matter.
gene: The unit of genetic information passed along from generation to generation through mating.
gillnets: Nets that capture fish as they try to swim through the mesh of the net. Used mostly by commercial fishers.
grading: The process of sorting fish by size.
heath tray: Tray used in hatcheries to raise eggs to the fry stage.
hen: Female fish.
homing: Ability to return or locate “home,” or a desired location.
hydroelectric facility: A dam; a place where electricity is made by falling water.
ice age: A period in geologic time, more than 10,000 years ago, when nearly one quarter of the earth was covered with ice.
imprinting: Behavior in which the first response to a particular stimulus, early in life, becomes a fixed response to the same stimulus thereafter.
inorganic: Made from material that is not from an animal or plant
interspace: The areas on a fish between the parr marks.
invertebrate: Does not have a backbone.
juvenile: A young fish or animal that is not mature.
larvae: An immature stage of development in many kinds of organisms.
lateral habitat: The calm water areas along the edges of a stream.
lateral line: A sensitive line along the side of a fish which senses changes in pressure.
leaf litter: Old fallen decaying leaves.
liberation truck: The specially equipped tanker truck that hauls fish to the place they will be stocked.
limiting factor: Factors that reduce the populations of living organisms.
marked fish: A fish that has had a fin clipped off, a dye sprayed on, a tag attached, or a wire implanted so it can be identified at a later date.
mash: Food pellets fed to young fish at the hatchery.
maxillary: The upper jaw bone of vertebrates, including fish.
midge: The larval form of any two-winged fly.
milt: A milky liquid from the male fish that contains sperm.
Miocene: The geologic time period between 12 million and 25 million years ago.
niche: The role that a fish or animal plays in the plant and animal community. The type of habitat it uses.
organic: Of plant or animal origin.
parasite: A plant or animal living in or off of another plant or animal, in a harmful way.
parr marks:Vertical lines on young fish which make them harder to see.
pectoral fin: Front steering fins on either side of a fish; corresponds to front legs.
pelvic fin: Lower fin on either side of a fish; corresponds to hind legs.
percolation: To trickle/flow through something.
physiological: Having to do with what goes on inside of a body.
plankton: A tiny animal or plant which floats in water.
raceway: A rectangular hatchery pond where water enters at one end and leaves at the other.
ray: The main supporting structures for fins of a fish, usually easy to see and count.
rearing: To raise young.
redd: The nest made by salmonids for their eggs.
respiration: The process of getting oxygen into the blood, either from the air or water. Another word for breathing.
riffle: Fast, shallow waters of a stream.
riparian zone: The vegetated area next to a stream/ river.
run: A population of fish that returns from the ocean at about the same time headed for the same place.
run-off: Excess water beyond the normal flow of a stream.
salmonid: Any fish of the salmon or trout group.
sediment: Fine particles of rock and sand that collect along a river bottom.
seine: A net weighted at the bottom that hangs vertically in the water and catches fish when its ends are drawn together.
silt: Tiny, fine particles, such as soil or sand, suspended in and deposited by water.
slime layer: The layer of mucous covering a fish that protects it from fungi, parasites, and disease.
smolt: A young salmon or trout that has turned a silvery color and is ready to migrate to the ocean.
spawn: The act of egg-laying by the female fish and fertilization
by the male fish.
species: A specific type of animal or plant that can breed and produce offspring only with its own kind.
sperm or milt: Milky substance produced by the male fish to fertilize eggs.
stocking: The process of releasing fish into a lake or stream.
stream velocity: The speed with which a stream flows.
streamline: A torpedo like shape that moves easily through the water.
substrate: Bottom material.
terrestrial: Belonging to the earth.
transpiration: An animal or plant giving off a watery vapor.
tributary: A side stream that joins a larger river.
vent: The tube with which the female fish deposits her eggs.
watershed: The land area where water collects and flows.
weir: A fence or enclosure set in a waterway for capturing fish. Also, a dam or obstruction in a stream to raise the water level or divert its flow.
yolk sac: Sack attached to a newly hatched fish containing a balanced diet for its early growth.
zooplankton: Microscopic and other very small animals in water, many of which are larval forms.