The following stat explanations are useful when you are trying to win the Finny Festival or Fish Races.

Unlockable	How to unlock
Boost	Determines how fast your fish will start off at the beginning of the race. It increases by 1 point when a fish is feed a Carrot. but the gender of your fish will change.
Endurance	Determines how long your fish can stay at its top speed. It increases by 1 point when a fish is feed a Petit Fish.
Power	This stat does not affect races. It is a stat used the Battle Tank.
Stamina	Determines how fast your fish can go. It increases by 1 point when a fish is feed a Evy.
Tenacity	Determines how badly the fish will try to win. It increases by 1 point when a fish is fed a Prickly.
Weight and Length	These two stats do not appear to affect how your fish will do in the race.