adipose fin- a small, fleshy structure with no rays or spines, situated on the midline of the back of the fish, behind the dorsal fin. Best seen on catfish species.
air bladder- a gas filled sac lying above the intestine, used by the fish for buoyancy.
anal fin- the single fin situated on the midline of the fish, behind the anus.
barbel- a fleshy, flap-like or whisker-like appendage (very small and hard to see on some minnows) found near the mouth. Used as a sensory organ. A good example is on the shovelnose sturgeon.
body depth- the greatest vertical distance between the midline of the back and the midline of the belly, the "height" of the fish.
body width- the greatest distance from one side of the body to the other.
caudal peduncle- part of the body between the base of the anal fin and the base of the tail fin.
scales- scales having a patch of small prickles on the exposed
scales- scales roughly round in shape, without prickles.
dorsal fin- a fin (or fins) situated on the midline of the back, having spines or rays, sometimes both.
ear flap- a flattened, flexible structuure extending back from the rear edge of the gill cover (operculum). Can best be seen on some sunfishes.
fin ray- a slender, rod-shaped structure that supports the membranes of the fins. There are two types of rays, soft rays and spines. Soft rays are jointed, often branches, and flexible near their tips. Spines are unjointed, unbranched, and usually sharp at the tip and stiff along the shaft.
scales- the scales found on gar, for example. rhomboid shape,
with an anterior, peg-like extension of each overlapped by the scale in
front of it.
gill arches- the series of curved, bony structures lying beneath the gill cover that support the gill rakers and gill filaments.
gill cover- the large, flat bone on the side of the head, covering the gills.
gill rakers- knob- or comb-like projections on the front edge of the gill arch. They serve to protect and clean the gill fillaments.
lateral line- a series of sensory tubes and pores that extend from the head along the side of the body.
lateral line scales- the scales that actually bear the pores and tubes of the lateral line.
operculum- the scientific name of the gill cover.
paired fins- the pectoral and pelvic fins.
pectoral fins- the farthest forward or uppermost of the paired fins.
pelvic fin- the paired fin located beneath or behind the pectoral fin.
pharyngeal arches- the pair of curved bones located in the throat that bear the throat teeth.
sensory canal- a branch of the lateral line that extends into the head of some fishes.
snout- the part of the head in front of the eye, not including the lower jaw. The "nose" of the fish.
soft dorsal- a dorsal fin containing only soft rays, or the soft-rayed hind part of the dorsal fin if both spines and soft rays are present (as in perches).
total length- the straight-line distance from the most forward tip of the snout to the end of the tail fin, when the mouth is closed and the lobes of the tail fin are squeezed together.