Over on the Science A GoGo site, they have an article titled, “Evolution Makes a Mockery of Fishing Policy”. The study used strong selective pressure on fish populations mimicking the policy of taking the largest fish in the population. What they found was that the populational response was an evolutionary one, that part of the populational variation was in body-size traits, and that the new population with much smaller frequency of large body size individuals reflects new population characteristics:
Walsh said that removing the large fish in each generation caused declines in many traits spanning the life history, physiology and behavior of the fish. “We know that commercially exploited populations of fish often are slow to recover when fishing pressure is reduced. Our research indicates that the over-harvested fish stocks are slow to rebound because fishing selects for evolutionary changes in the life history of the fish. Because the changes in the fish are genetic, they don’t immediately go away when fishing ceases,” he concluded.
Not surprising, really, given the classic studies of John Endler on guppy evolution in Trinidad streams. Guppy populations under strong selection by predators tend to have smaller, more drab males, as the larger, more colorful males are more attractive to both females and predators. What we have in commercial fishing is a situation that can be cast in much the same way, with humans as the predators.
Unfortunately, it would be unusual for an insight from biology to actually make a difference in setting fish stock management policy. Where biological concerns have been raised in the past, it has been all too common that political concerns overrode them. Perhaps a smaller fishery many years ago on various over-fished stocks could have prevented the precipitous declines that have been seen in recent years. The management decisions that permitted continued higher levels of take than were supported by the biological data emphasized the short-term benefit of higher employment in the fishing industry, ignoring the long-term cost that is now presenting its bill. The resulting unemployment rate is, I think, going to be far higher than the projected reductions that caused policymakers to set aside the relevant biology.