Swimming dynamics in fish Flashcards
How are fish body muscles arranged?
Muscles are arranged in segments called myotomes. They are separated by collagenous sheets called Myoscepta. Myotomes are W shaped 3d structures.
How do fish contract myotomes to get forward thrust?
When myotome blocks on one side of the fishes body contract the body moves that way. Separate waves of contraction move down either side of the body backwards. These cause the body to push against the water and give thrust.
Whats the difference between eel movement and more advanced tuna movement?
In eels the waves pass down the whole body including the head- inefficient. In tuna the contractions are confined to the posterior of the fishes body- more efficient.
How do fish counteract the downward force of their weight in the water ?
Using swim bladders filled with lipids and air.
How is drag related to swim speed ?
As swim speed increases, drag increases logarithmically.e.g as speed doubles, drag quadruples .
What units are used to measure swim speed in fish ?
Body legnths per second (BLS-1)
What are the two types of drag against fish?
Skin friction drag and pressure drag.
What Width: length ratio is best in fish to minimize drag?
0.25.
What features on most fish reduce the effects of turbulence and optimize laminar flow?
- Mucus is secreted onto the surface f the scales
- Microirregularities in the fishes skin may help maintain laminar flow
What feature does caster oil fish have to increase laminar flow?
They have Ctenoid scales that create small vortexes that keep the boundary layer intact.
What is the Aspect ratio of a fin and give examples of low and high?
(SPAN) ^2 / SA. High Ar = Fast prolonged speeds with low drag e.g tuna Low AR have great maneuvorabiliy and acceleration and high drag e.g salmon.
What fins act as hydrofoils to generate extra lift ?
Pectoral fins and heteroceral fins in elasmobranchs.
At what speed is the aerobic capacity reached in fish ?
Can they travel faster ?
4Bls -1. They can travel faster 30Bls-1 in small fish and 20Bls-1 in larger fish. However they will become exhausted after around 20 seconds at this speed.
What is cruising and it’s advantage?
The ability of fish to be able to swim at slow speeds indefinitely. Meaning they are able to migrate
