Fishing is a particularly lucrative business in Runescape. Like mining for Rune Essence, fishing allows you to provide others with materials that they can use to profit from others. In short: People need fish. They want to raise their cooking skills, or they’ll want to take it in battle (lobsters can be very useful to regain health).
Now, fishing is a business. It’s not just about getting your skill up. However, if you want to make a large profit from the fishing trade, then you will need a skill of at least 50. Players will pay rather handsomely for marlins and lobsters, a.k.a lobbys, because of their large benefits in combat some players will offer a fisherman up to fifty gold pieces for each one of these fish!
To get your skill up easily, you will need to start small. You are given a net at the beginning of the tutorial with which you can catch shrimp and anchovies. If you keep at it for a few hours, fishing for these simple creatures will get your fishing skill up very quickly. The fish themselves are not worth that much, maybe one gold piece each, but the constant use of the skill will help you greatly. If you are feeling greedy, or just “efficient” you may want to build up a small stockpile of these almost worthless fish in your bank account you can use them to practice other skills such as cooking, or even sell them in myriads.
Once you have graduated from the net, you will be able to use fly fishing rods and fishing rods. Of course, you will need to buy the appropriate bait for this for traditional fishing, you will need “bait” and for fly fishing you will need flies. All of these can be bought in local shops near seaports, and they are relatively cheap. When catching fish such as tuna, you will gain more experience than by catching shrimp, but you will be using resources bait doesn’t last forever. You will need to constantly replenish your supply of bait and flies. Yet, if you truly have a lot of free time on your hands, you can just stick to the net it’ll take a long time, but in the end it helps you level up just the same.
Once you have achieved the level that allows for spears and cages to be used, you are all set to start making some serious gold. Take your spears and cages to the island of Karmaja, which is accessed by a ship in a seaport. The trip only costs thirty gold pieces, and the fish that are available can easily sell for that apiece. The island is perfect for catching lobsters and marlins, which will sell well in player-controlled markets.
If you are really into the fishing business, try finding a clan that is fishing-oriented. You may in fact be able to find large groups of people who collectively pool their catch and send middlemen out to sell it for them. And if you cannot find such a group start one.