atm moment fishing is useless unless you want those achivements.
I suggest to make fishing usefull for provisioring and alchemy.
Fish shall be an ingredient for alchemy and provisioring.
For alchemy, the fish shall be used as booster for potions.
For example:
Water+ alch. Ingredient+ alch. Ingredient+ alch. Ingredient+ Fish
Longfin increases the duration of the potions.
Dhufish increases the stamina restoration of the potions.
Salmon increases the magicka restoration of the potions.
and so on.
The rare fish shall be used too and they may increase two or tree stats of the potions.
For provisioring, i suggest to make the recipes with fish more powerfull then common ones.
btw make more rare recipes with rare fish as an ingredient or maybe rare fish for legandary recipes