ok firstly im gonna divide this into 2 parts 1 for f2p 1 for p2p.
P2P: ok if u wanna be a pro fisher i highly recommend for you 2 fish monks (monkfish) they can be found at the piscatoris fishing colony. you need 62 fishing and have won the swan song quest including a very high lved monster the 170 seatroll queen. after that you can fish them. they have extremely fast catch speed and sell from 450-550gp each. you could also fly fish salmon and trout off the river in shilo village. they do get you fishing xp about 1-3% quicker than monkfish but u make about 80% less profit out of them. also requires completing shilo village quest to even begin fishing here.
So go with the monks they r the best!!!!!!!!!!!!!!!
F2P: if u wanna get higher fishing level but are only a f2per the i reccomend for you to catch lobbys (lobster) off the dock on Musa point (Karamja). you could fish them in mid wildy but you will have a more than possible chance of seeing revs plus its about a 5min walk to the next bank. anyway back to musa point fishing. you will need 30gp (another 30gp if ur gonna travel back to sarim by ship.) i also reccomend you try 2 win the medium lummy acheivement diaries so that u get the cabbage port ring. this is extremely useful as it teleports you straight back next to draynor village which is the closest bank to sarim (unless you include the sarim deposit box but then you will need 2 pile all ur cash that ur gonna use.) And if u have the ring u will have a free space in ur inventory instead of travelling back cash. some other players prefer to catch swordies and tuna with a harpoon. this has the exact same process as lobbys but instead u cathc 2 fish at a time.
So go with either harpoon or lobby pot but my choice is lobbys. thats what i caught b4 i was a mem and even wen i was a mem i caught them from catherby, then the guild. at 69 i started catching monks. my fishing lv is 85 2day but will most likely b higher than that wen u r reading this.
well gl with ur fishing and have fun with ur cape!