Analysis of fisheries suggests marine ecosystems can recover

A recent study provides evidence that efforts to rebuild depleted fish stocks are worthwhile, finding signs of recovery in five major marine ecosystems. Diverse management tools can successfully balance conservation with commercial fishing, allowing fish stocks to recover in overexploited areas, say the authors.

Overexploitation of fish stocks has serious consequences for the sustainability of fisheries and for the healthy functioning of marine ecosystems around the world. Yet efforts to restrict fishing are often resisted by fishermen concerned by short-term social and economic impact, especially those whose livelihoods depend on fishing.

An international team of researchers evaluated the condition of marine fisheries and the effects of fishing in 10 of the world's largest marine communities. The study examined the range of fishing rates that could provide high yields while maintaining most species from both a commercial and conservation perspective. In addition, they investigated management programmes which were successful in rebuilding marine ecosystems.

The research demonstrated fishing levels had been substantially reduced in five of the 10 ecosystems studied: Iceland, Newfoundland-Labrador, the Northeast US Shelf, the Southeast Australian Self, and the California Current ecosystem. Clear signs of rebuilding were seen in several of these.

The study examined less than a quarter of the global ecosystems used for fisheries, all of which were intensively managed. Of these areas, 63 per cent need to be rebuilt. 14 per cent of assessed stocks had collapsed by 2007, although results varied regionally. For example, few assessed fish stocks had collapsed in the eastern Bering Sea, whereas 60 per cent had collapsed in eastern Canada.

However, progress was highlighted in Kenya: successful management strategies involving cooperation with local communities together with restrictions on damaging fishing gear and the introduction of protected areas has increased fish stocks, the size of fish caught and improved incomes from fishing.

A trade-off between allowable catches under fisheries and conservation of vulnerable or collapsed fish stocks is possible under well-designed management systems. Collapsed stocks can be rebuilt if traditional methods such as catch quotas and community management are combined with strategically placed fishing closures (depending on local conditions), gear restrictions, widespread ocean zoning to separate areas managed for fisheries and for species and habitat conservation.

Rebuilding may take decades and will involve short-term costs, especially reduced yields and the loss of jobs. A global view is needed as those who depend on fisheries in poorer regions may have no alternative food sources and incomes. In addition, developed countries should not shift fishing pressures to less developed areas of the world: strong governance is required to enforce compliance with rebuilding efforts. Local differences between fisheries, ecosystems and governance need to be considered when developing management strategies.

Ideally countries should take action before overexploitation becomes evident. The study found that only Alaska and New Zealand had the foresight to act before that stage was reached.

Source: Worm, B., Hilborn, R., Baum, J. et al. (2009). Rebuilding global fisheries. Science. 325: 578-585.

Contact: bworm@dal.ca and rayh@washington.edu