Here is my data on the exp values of different catchables:

Bottle 1-3
Tire 1-3
Bass 1-3
Black Bass 1-3
Tadpole 3-6
Clown Fish 2-5 (?)
Dab 6-8 (?)
Noob 8-17
Eel 10-30 (?)
Blue Snapper 10-12 (?)

The actual exp you get is random in the possible range.
Because of this randomness, it is hard to find out how much exp a certain fish gives on average, because you need to catch each fish once when it gives you its lowest amount of exp and once when it gives you its highest amount of exp. Tracking all this data is time consuming and annoying, so I just gave up.