1. Fish Locomotion

2. Swimming by Fishes Most economical form of movement by animals
Bouyed by water
No energy needed to counter gravity

3. Swimming by Fishes Squirrel - 1 km walk - 5.43 kcal
Gull - 1 km flight kcal
Salmon - 1 km swim kcal

4. 3 types of swimming Sustained swimming - slow Burst swimming - fast
Prolonged swimming - medium

5. 3 types of swimming
Sustained swimming - slow body lengths per second
Foraging over large areas, long-distance migrations
Aerobic - no oxygen debt

6. 3 types of swimming
Burst swimming - fast - up to 20 body lengths per second
Escaping predators, capturing prey, swimming against currents
Anaerobic - oxygen debt

7. 3 types of swimming
Prolonged swimming - intermediate - ~ 10 body lengths per second
Used as situation demands
Aerobic and anaerobic

8. Locomotion Most locomotion accomplished through use of caudal fin
Fastest fish - barracuda - 27 mph

9. Locomotion
Propulsive muscles along side of fish are W-shaped myomeres (myotomes)

10. Locomotion
Moves by contraction waves of myomeres moving posterior along one side
Creates sinusoidal movement of body by alternating contractions on one side of body, then the other

11. Fish Locomotion Primary forces involved in fish swimming:
Thrust - force that propels forward
Drag - friction produced from passing an object through a medium
Gravity – force from earth’s magnetic pull (partially counterbalanced by density of water)
Lift - upward force that counteracts gravity

13. Swimming Styles - Thrust Generation
Body waves – Anguilliform
Partial body waves – (Sub)Carangiform
Caudal peduncle/fin beats – Ostraciform
Medial fin waves - Amiiform
Pectoral fin beats -Labriform

14. Swimming Styles Body waves Anguilliform (eel-like)
Lateral curvature in spine and musculature that moves in a posterior direction
Start: lateral displacement of head, and then passage of this displacement along the body axis to the tail
Result: backward-facing “wall” of body pushing against the water

15. Swimming Styles Partial body waves (Sub) Carangiform, Thunniform (tuna-like)
Body wave begins posterior to head and increases with amplitude as it moves posteriorly
Reduced drag compared to full body wave swimming
Wave STARTS at the caudal peducle (deeply forked, lunate)

16. Swimming Styles Caudal peduncle/fin beats Ostraciform (boxfish-like and puffer-like)
Sculling action of caudal fin—like rowing
No body waves - body remains rigid - useful for odd-shaped fishes

17. Swimming Styles Medial fin waves Amiiform - bowfin-like
Body rigid, but medial fins generate posterior waves (forward) or anterior (reverse)
Good for stalking or moving without disrupting body musculature that serves as electric organ (knifefish)
Also used for sculling - triggerfish & others

18. Swimming Styles Pectoral fin beats Labriform wrasse-like Similar to rowing laterally-positioned pectoral fins- often includes feathering as well Especially useful for fine maneuvering e.g. by deep-bodied fishes

19. Locomotion video

20. Drag Reduction Features in Fish
Fusiform body shape
Reduction of body wave amplitude
Reduction of fin surface area:
caudal fin (forked, lunate)
paired and medial fins
Boundary layer modifications
mucous
laminar jets of water
microprojections

21. Fusiform body shape pointed leading edge
maximum depth 1/3 body length back from head
posterior taper
“propeller” (caudal fin) interrupts perfect fusiform shape

22. Body wave modifications
Minimize lateral movement of head to reduce drag - subcarangiform
Increase amplitude as wave moves in posterior direction
Ultimate expression involves no body waves, but alternate contraction and transfer of body musculature energy to caudal peduncle and caudal fin - thunniform

24. Fin surface area reduction
Area of fins increases drag
Permanent design modifications: forked caudal fins, reduced length of medial fins
Adjustable design modifications: variable erection of fins - allows for minimizing surface area when fin is not needed for thrust or turning - ultimate expression: fairings in tunas (dorsal and pectoral fin pockets)

25. Boundary layer modification
Layer of water immediately adjacent to skin causes most of friction - boundary layer
Thickness of boundary layer is proportional to amount of friction
Three approaches to reducing thickness of boundary layer:
smoothing it - making it “slicker”
roughing it - giving it tiny disruptions (golfers learned from sharks??)
shortening it - reducing distance of contact

26. Boundary Layer, continued
Fluid jets - from gill chamber and out operculum or in micropockets behind and beneath scales
Mucous - slime adds to “slipperiness”, can reduce drag by up to 65%
Microprojections - disrupt boundary layer so it cannot grow:
ctenae
placoid tips

27. Buoyancy Control in Fishes
Dynamic lift: generated by propelling a hydrofoil forward at an inclined angle of attack
Static lift: generated by including low-density substances and reducing mass of high density substances in body.

28. Dynamic Lift
Hydrofoils: fish use their fusiform body and some use their pectoral fins as hydrofoils
Amount of lift is determined by: angle of attack and speed of propulsion
Ultimate expression of this is in pelagic rovers - tunas, mackerel sharks
head, pectoral fins and peduncle keels all used as hydrofoils
swim constantly

29. Static Lift Reduction of high density substances:
cartilage less dense than bone
use design features in bone that increase strength while reducing mass of bone
Inclusion of low-density fluids
lipids - squalene in sharks (sp. grav. = 0.86)
stored in liver
gases - in swim bladder
only in bony fishes

30. Swim bladders
Gas-filled “appendix” to the anterior digestive system - dorsal to abdominal organs
Two types of swim bladders:
physostomous - pneumatic duct connects swim bladder to esophagous
physoclistous - no connection between swim bladder and gut