What is a Fish?
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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
Flexible Body
Thick Caudal
Peduncle
Large Gape
Maxilla may or may not
be excluded from gape
Posterior-placed
Median Fins
Cruising Specialists –
Adaptations for Sustained Swimming
Terminal
Mouth
Finlets
Fusiform
Body
bluefin tuna – Thunnus thynnus
Lunate
Tail
Caudal
Keels
Narrow Caudal
Peduncle
Maneuvering Specialists –
Adaptations for Suction Feeding
Laterally Compressed Body
Small Gape
Maxilla
Excluded
From Gape
Laterally Positioned Pectoral Fins
Adaptations for Bottom Dwellers
Barbels
Inferior Mouth
Dorso-ventrally
Compressed Body
Adaptations for Surface Dwellers
Superior
Mouth
Counter-color
Shading
Fish Identification: Color … ?
Fathead
Minnow
(Pimephales
promelas)
Fish Identification: Size… ?
Fish Identification : Patterns
white bass (Morone chrysops)
- stripes
yellow perch (Perca flavescens)
- bars
northern pike (Esox lucius)
- spots
Fish Identification : Patterns
red drum (Sciaenops ocellatus)
- eye spot
white shark (Carcharodon carcharias)
-counter-color shading
Fish Identification: Fins
Spiny 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 thoracic
position (derived state)
Pelvic fins in abdominal position (more primitive)
Fish Identification: Shapes
Forked
Fins
vs.
Rounded
Body
streamlined
vs.
deep
Scales
vs.
diamond
round
superior
Mouth
inferior
terminal
vs.
vs.
Fish Identification : Unique Features
Barbels
Teeth
Northern Pike
Tadpole Madtom
Scales
Lateral line
Brook Stickleback
Golden Shiner
Fish Scale Types
Fish Scale Types