What is the function of an adipose fin in (cat)fishes?
No one is really sure what the exact function of an adipose fin. The two most plausible theories have to do with swimming. (1) The adipose fin functions to control vortices enveloping the caudal fin during swimming (these vortices would reduce swimming efficiency). (2) adipose fins are a passive precaudal sensor of turbulent flow (again, this has to do with swimming efficiency). Experiments have been performed on young salmonids that show that the amplitude of movement of the caudal fin increases significantly in individuals of a certain size when the adipose fin is removed. However, the jury is still out as to the exact function of the adipose fin.
