No but seriously. If you plan to straight up sell the fish (on average, all 3 are around 5gp ea to sell maybe even less or nothing if you just drop them).
I guess 6-7 GP/XP if using the highest Porter + Bringing 5 urns per 30 minute trips!
Ava + Fishing Outfit can reduce the GP/XP a bit though.
Assuming it costs 400gp per item to bank (since most people clearly overpay buying items) and you either sell the items back. That's like 6gp/xp per fish.
I also found Ava to be better than Granite Lobster anyway though doesn't hurt to have a slave have ava there whilst you have Granite Lobster active.
I don't find it anymore AFK than using the action bar to drop it though (if you place your bar at the bottom and turn on one click button on, you can spam left click to drop the fish iirc).