If not on Siege:
Fishing was always slow gaining. Only that we fishers are more patiently than the tamers.

(Let aside the time of 8*8 when fishing was easy to gain.)
Besides that is 80+ fishing now a fine point to learn the way of a fisherman. With High Seas (or maybe even with SA) some old restrictions fell. At your lvl you now can get sea serpents with mibs. You could fish up treasure, if you have some mibs from t-chests. If you later plan to do fishmonger quests, you should start to build up a decent stock of deepwater fish and crabs/lobsters. If you want to speed up gains a little, you could go for crab fishing (high seas necessary). I can set out about 30 traps in 1 Minute. (And need maybe another minute to pick them up afterwards and empty them.) The gains might not be better than fishing with a pole, but you bypass the timer of the fishing pole that way, getting more chances to gain in the same amount of time. You only have to remember, that you need to fish in deep water for gains and the same counts for fishing with traps.