Fish Morphology

Fish body and tail shapes

1. FISH MORPHOLOGY

2. Fish Morphology
•There is a great diversity in
shapes of fishes and their body
parts
•Shapes of fishes are adaptations
to the species’ environment
and/or behaviors

3. Body Shape - Fusiform
•Streamlined, torpedo-shaped
•Fast-swimming fish
•Predators, live in open water
•Move tail side to side
•Examples: tuna, swordfish, shark, striped bass
side view front view

4. Body Shape - Compressiform
•Compressed from side to side
•Quick bursts of speed over short distances
•Live among plants and move in narrow spaces
•Examples: moonfish, angelfish
•Move tail side to side
front view

5. Body Shape - Depressiform
•Flattened top to bottom
•Live on bottom
•Slow
•Flap fins up and down and swim like a bird
•Examples: flounder, skates, rays
front view

6. Body Shape – Filiform (Attenuated)
•Elongated shapes
•Live in soft mud, sand or under rocks
•Slow
•Slither like a snake
•Examples: eels, sand lance
side view

7. CAUDAL FIN SHAPE
•Caudal fin = tail fin
•Homocercal – symmetrical
•Heterocercal - asymmetrical

8. Caudal Fin Shape –
Homocercal - rounded
•Large amount of surface area allows sharp
turns and quick starts – to avoid predators
•Creates drag – fish tires easily
•Example: northern puffer, clownfish

9. Caudal Fin Shape –
Homocercal - truncate
•Allows short bursts of speed to escape
predator or constant slow swimming
•Less drag than rounded
•Bottom-dwelling fish
•Example: killifish, flounder, sculpin

10. Caudal Fin Shape –
Homocercal - forked
•For constant swimming over long distances,
reduces drag
•Open water fish
•Do not need speed to feed or for protection
•Examples: many schooling fish, pilot fish
menhaden

11. Caudal Fin Shape –
Homocercal - lunate
•Half-moon shaped
•Fast moving, oceanic fish
•Less drag, great acceleration, reduced
maneuverability
•Examples: tuna, swordfish

12. Caudal Fin Shape –
Heterocercal
•Medium speed
•Asymmetrical – top longer than bottom
•Provides lift when no air bladder
•Reduced maneuverability
•Example: many sharks
blue shark