Although most anglers keep their catch for consumption, catch and release fishing is increasingly practiced, especially by fly anglers. The general principle is that releasing fish allows them to survive, thus avoiding unintended depletion of the population. For species such as marlin, muskellunge, and bass, there is a cultural taboo among anglers against taking them for food. In many parts of the world, size limits apply to certain species, meaning fish below a certain size must, by law, be released. It is generally believed that larger fish have a greater breeding potential. Some fisheries have a slot limit that allows the taking of smaller and larger fish, but requiring that intermediate sized fish be released. It is generally accepted that this management approach will help the fishery create a number of large, trophy-sized fish. In smaller fisheries that are heavily fished, catch and release is the only way to ensure that catchable fish will be available from year to year.