Hydrodynamics: Fin Variation Flashcards
Caudal Fin Variation
Rounder caudal fins in slower moving fish (Low Re)
Increased indentation for faster fish (high Re)
This occurs over its life cycle as well: rounder as younger
Purpose of tail fork
Moves more of the tail outside of turbulent region
Heterocercal Tail Purpose
Longer lobe on top due to convex body on top surface.
Allows for more of tail to be outside of turbulent zone
Purpose of tail fork
Causes turbulence to go to the middle
This means no thrust where there is turbulence
Pinched Keel
These exist near the back of the fish
They force water to go faster velocity
Pushes turbulence further back
Leopard Shark Heterocercal Tail
This is classical
Upper lobe leads and generates lift
Sturgeon Heterocercal tail
Non-classical
The lower lobe leads
does not generate lift
Bluegill homocercal tail
The tail is symmetrical
But the upper lobe moves faster and generate lift
How do salmon maintain position in stream
Slalom using vortexes of stream to maintain position
Use very little energy
Previous thought on adipose fin
sub-carangiform swimmers
no rays or muscles, passive
thought to vestigal
Retained in 8 orders
Clipping does not effect swimming In fish
Importance of Type of clip
If you clip fin halfway up
It will grow back
Clipping near the base causes pain in the fish
Purpose of Adipose in Salmon
When swimming
The adipose flaps passively back and forth
The caudal fin beats in accordance with the adipose movement
The removal of adipose causes 10-15% increase in amplitude of caudal fin
Use more energy without adipose fin
Stiff tubes of nerve sheaths to detect pressure
Catfish adipose findings
Catfish from higher flow environments have more species with adipose fins
Lanterfish Adipose fin
complex neaural anatomy
Thought tobe for vertical migration
Detection vortices during their movement up and down
