Why not cook all the fish instead of selling them, you will have a few thousand left over to sell as well as another 99 skill, no point in selling the fish as you can only make 30 mill which can't even buy all the logs and bow strings for fletching not to mention nats if you cook them you will have all the food + more for 99 theving and agilty + 99 cooking. I say you should use nats to make your money and use the fish for training etc.