Rebuilding Global Fisheries

August 25, 2009

Generations of overfishing has left the majority of assessed fish stocks worldwide in need of rebuilding, according to a recent report published in Science Magazine.

Generations of overfishing has left the majority of assessed fish stocks worldwide in need of rebuilding, according to a recent report published in Science Magazine. The report, generated by marine ecologists and fishery management scientists, found that even as conservation efforts make headway, lower exploitation rates are needed to reverse the collapse of vulnerable species.

In the past, management scientists were less concerned if a fish species was sustaining itself – even if it fell to 40 or 50% of its norm. Meanwhile, ecologists characterized this same fish species as being depleted. Now, this unusual collaboration between ecologists and management scientists – the first of its kind – sheds light on the ongoing debate about the best means to achieve sustainable fishing practices.

“We held a series of workshops between the two groups over a period of two years, agreed on questions to ask and data to look at. By coming up with a common vision of the status of fisheries and how to achieve both conservation and management objectives, we have set an agenda for progress in fisheries management,” says Dr. Ray Hilborn, Professor, School of Aquatic and Fishery Sciences at the University of Washington in Seattle.

After debating the issue for some time, the two sides pooled their data to find common ground, and the results of their discussion was simultaneously encouraging and disconcerting. In five out of the 10 well-studied ecosystems, the average exploitation rate declined and hovered at or below the rate predicted to achieve sustainable yield. Because of historical overfishing prior to the mid 1990s, 63% of assessed fish stocks are still below the target level of abundance.  Two of the 10 ecosystems have never been overfished, leaving three where exploitation rates still remain above the levels that produce maximum sustainable yield (MMSY).

The struggle to curb overfishing due to stressful social and economic barriers cannot be dismissed, as there are numerous costs and benefits involved in rebuilding depleted fisheries. However, some management practices work better than others. This study found that sustained management for lower exploitation rates could promote greater stability than a more traditional prescription that abides by exploitation rates that produce MMSY.

“We argue for exploitation rates lower than that to have less ecological impact, and higher stock abundance leading to higher daily catches and more profitable fishing,” says Hilborn.

In other words, the MMSY (a calculation of the maximum number of fish from an ecosystem that can be caught sustainably in a region without threatening the stock) should be reinterpreted as an upper limit rather than a management target – a concept that Hilborn says is not radically new, but simply put in the context of current practice in a number of ecosystems. Meanwhile, the study encourages that the health of the wider marine environment be taken into consideration as well when designing management actions.

There is little doubt that some combination of traditional approaches (like catch quotas) with modern initiatives (like fish closures and economic incentives) is necessary to restore marine fisheries and ecosystems. Yet there are still many hurdles to overcome. Illegal fishing in the developing world could threaten food security and biodiversity. And short-term costs are inevitable. 

“Fishermen pay the major cost of rebuilding, but some of the costs are passed on to consumers in the form of higher prices due to less fish on the market,” says Hilborn.

To ensure the health of marine fisheries for generations to come, this is a price that scientists and ecologists believe consumers will be willing to pay.


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