What is a Fish?

• Poikilothermic – body temperature is identical to surrounding water• Chordates – have developmental characteristics of all vertebrates• Appendages developed as fins• Chief respiratory organs are gills• Body generally covered with scales

“A fish is an aquatic vertebrate with gills and with limbs in the shape of fins” (Nelson 1994)

There are over 25,000 fish species, so there are exceptions to these general characteristics.

Fish vs. Fishes

“This tank is full of fish.” “The ocean is full of fishes.”

Anatomical Terminology

Functional Morphology in Fishes

Functional Morphology – “the study of form and structure in animals as related to the functions of the various body parts”W.A. Gosline, 1971

From P.W. Webb, 1984

Acceleration Specialists –Adaptations for Ram Feeding

Posterior-placedMedian Fins

Large Gape

Thick CaudalPeduncleFlexible Body

Maxilla may or may notbe excluded from gape

Cruising Specialists – Adaptations for Sustained Swimming

bluefin tuna – Thunnus thynnus

LunateTail

CaudalKeels

Finlets

FusiformBody

Narrow CaudalPeduncle

Terminal Mouth

Maneuvering Specialists – Adaptations for Suction Feeding

Small Gape

Laterally Compressed Body

Laterally Positioned Pectoral Fins

MaxillaExcludedFrom Gape

Adaptations for Bottom Dwellers

Barbels

Inferior Mouth Dorso-ventrallyCompressed Body

Adaptations for Surface Dwellers

SuperiorMouth

Counter-colorShading

Fathead Minnow(Pimephales promelas)

Fish Identification: Color … ?

Fish Identification: Size… ?

Fish Identification : Patterns

white bass (Morone chrysops)- stripes

yellow perch (Perca flavescens)- bars

northern pike (Esox lucius)- spots

Fish Identification : Patterns

white shark (Carcharodon carcharias)-counter-color shading

red drum (Sciaenops ocellatus)- eye spot

Fish Identification: FinsSpiny Dorsal Fin (protection, steering, braking)

Soft Dorsal Fin (forward propulsion, steering, braking)

Caudal Fin (forward propulsion)

Anal Fin (forward propulsion)

Pectoral Fin (braking, steering, propulsion)

Pelvic Fin (braking, steering) Adipose Fin (Ictaluridae, Salmonidae)

Pelvic fins in thoracicposition (derived state)

Pelvic fins in abdominal position (more primitive)

Fish Identification: Shapes

streamlined

Forked

Rounded

deep

Fins

Body

Mouth

Scales

vs.

vs.

vs.

vs.

round diamond

vs.

superior terminal inferior

Fish Identification : Unique Features

Tadpole Madtom

Brook Stickleback

Golden Shiner

Northern PikeBarbels Teeth

Scales Lateral line

Fish Scale Types

Fish Scale Types