There is hope for some species that were overexploited if fish limits are respected. (Photo Credit: Helene Petit/WWF)
Some depleted stocks still can recover, others can not
Monday, April 22, 2013, 04:00 (GMT + 9)
A new study by Rutgers University shows that fish species that have been overfished for decades can be brought back to health more easily than originally thought, once limits are placed on fishing.
Marine scientists reported that a fish stock’s ability to recover from overfishing is enhanced even if it has been moderately overexploited for decades, possibly allowing for a quick recovery if sensible catch limits are enforced.
Philipp Neubauer, a postdoctoral scholar, and Olaf Jensen, an assistant professor of marine and coastal sciences, claim the key is in the adaptation of fish to overfishing. They hypothesize that many overfished species have adapted to being so and mature at a younger age, letting them recover relatively quickly if limits are put on fishing to give the stock time to rebuild.
The results were published recently in the magazine Science.
“Recovery of overexploited marine populations would be a ‘win-win’ for fisheries and conservation, easing pressure on wild populations and associated ecosystems, and ultimately enhancing catches, revenues and food security,” Neubauer and Jensen wrote.
Neubauer used to think that decades of overfishing would be too much for a fish population and mean a slow recovery once fishing pressure was reduced.
“My hypothesis, based on prior studies, was that marine stocks that had been overexploited for a long time would have a harder time coming back,” he said. “So this was a bit of a surprise.”
Neubauer, Jensen and colleagues examined 153 fish and invertebrate stocks across the oceans that had withered to less than 50 per cent of their maximum sustainable yield, and used all available data from fisheries managers around the world.
“We actually used a statistical method borrowed from medicine, called survival analysis,” Neubauer said. “What medical researchers do is look at how long it takes, under a particular treatment, to recover from a disease. We looked at fish stocks as if they were patients undergoing treatment and examined the data to determine how long it would take each stock to recover.”
Conversely, the bad news is that species which has been overfished intensely for a short time have a much more difficult time rebounding, and this may also be the cause for fish that reproduce slowly and have been severely overfished, such as Atlantic halibut.
Jensen and Neubauer said that fisheries managers must recognize overexploitation early and put effective limits on the catch for a stock to be able to recover.
Jeff Hutchings, a professor of biology at Dalhousie University and one of the authors of the study, explained that recovery is fairly unlikely now for depleted cod stocks because Canadian fisheries managers did not react soon enough. In Canada, the federal government must set a population threshold to determine when action must be taken to ease fishing on a fishery so that depleted stocks can recover as they have in the US, The Canadian Press reports.
By Natalia Real