Current fishing policies among sport fisheries dictate that young, small fish that are caught be thrown back into the water and encourage participants to catch bigger, older fish. This week's issue of the journal Nature has U.S researchers saying this policy is all wrong and should in fact, be the opposite.

"That type of regulation, which we see in many sport fisheries, is exactly wrong," George Sugihara of the Scripps Institution of Oceanography at the University of California San Diego said in a statement. "It's not the young ones that should be thrown back, but the larger, older fish that should be spared. Not only do the older fish provide stability ... to the population, they provide more and better quality offspring."

Older, larger fish will not flucuate in size if food is abundant or scarce, wheras younger, smaller fish may rapidly mulitply in numbers or face a population collapse depending on the availability of food. After the California sardine fishery collapsed in the 1940s, they set up a study of fished and unfished species, which is where the information was gathered for this report.

Nils Stenseth of the University of Oslo said fishing practices that stress taking only the oldest and biggest fish can actually force quick evolutionary changes in the fish populations.

"Many recent studies have provided evidence for this ... effect, and show that the ecological-evolutionary consequences of harvesting can occur at a much faster rate than previously thought," he wrote in a commentary.

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