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
