Monkfish give 10 more Fishing experience per catch than sharks, are caught much faster, and can be fished at a lower Fishing level than raw sharks. This makes monks a very efficient way of levelling up. In addition, cooked monkfish are lighter, so players engaging in a lot of running can run longer carrying monkfish versus carrying sharks. The only downsides are that sharks are more valuable and give more Cooking experience (although that does not matter if the raw fish are sold).
Raw monkfish can be cooked at level 62 Cooking, and yield 150 experience if they are successfully cooked. Players will stop burning raw monkfish at level 92, or 90 with Cooking gauntlets, which require completion of Family Crest. At level 62, the burn rate is roughly 25%. At level 83, the burn rate with cooking gauntlets is approximately 3.7%, based on a sample size of 1800 monkfish with a margin of error of no more than 1%. This means that you are expected to burn between 28 and 46 monkfish for every 1000 you cook.