While better scientific analyses may help reduce worldwide overfishing and depletion of many ocean fish species, new management systems must be instituted to shield global marine fisheries from the political pressures to over-fish, according to a team of scientists led by a researcher at the University of California, Davis. In a paper appearing in the July 25 issue of the journal Science, the researchers suggest that the major cause of overfishing is political pressure to protect jobs and sustain short-term profits by increasing the fish harvests. The economic justification for bigger harvests prevails, in part, because it is inherently difficult to predict future fish populations. "The challenge for the next century lies in crafting new local and regional institutions, not just in filling the scientific gaps," said Louis W. Botsford, a wildlife and fisheries biologist at UC Davis. "The best hope for greater sustainability of fisheries is to insulate management from pressures for greater harvest, while attempting to reduce uncertainty through a comprehensive ecosystem view." Collaborating on the study with Botsford were Juan Carlos Castilla of the Pontificia Universidad Católica de Chile in Santiago, Chile, and Charles H. Peterson of the University of North Carolina at Chapel Hill. Ocean fish provide an important source of food, accounting for 19 percent of all animal protein eaten by humans. Furthermore, they are the basis for an industry that employees 200 million people worldwide and produces an annual catch valued at $70 billion. But fisheries around the world, including many in the United States, are in trouble, note Botsford and colleagues. They point to a recent report by the United Nations Food and Agriculture Organization indicating that global fisheries in the 1990s are leveling off at about 100 million tons caught annually. And nearly half of the individual commercial fish species are fully exploited, while another 22 percent are over-exploited. Recent examples of overfishing include the collapse of the cod and haddock populations off of the East Coast of the United States and Canada. Perhaps this sorry state of affairs should come as no surprise. Marine ecosystems --ranging from coastal to deep-sea communities of fish, mammals, turtles, birds and plant life -- are complex. They are directly impacted not only by human enterprises, such as fishing and pollution-producing activities, but also by large-scale fluctuations in weather and climate. Fisheries scientists have long been concerned with annual changes in weather and physical oceanographic conditions, but in recent years they have come to realize that periodic long-term changes also have profound influences even on fish stocks that are separated by great distances. One such example is the El Niño-Southern Oscillation, a warming of the waters in the eastern Pacific Ocean that occurs every five to 10 years. (Scientists believe we are at the beginning of another large El Niño.) Another example is the warming of waters off of Alaska in 1976, believed to have triggered important biological changes that are still in effect, including an increase in the Alaskan salmon catch and a drop in salmon catches from California waters. Clearly, the undersea worlds are a challenge to probe and even more perplexing to wisely manage. While better understanding of the physical variabilities, such as the large-scale weather and climate shifts, will yield sounder information on which to base management decisions, the political pressures on fisheries management still must be alleviated, Botsford stressed. "Most overfishing is due to the 'ratchet-effect,' which occurs when -- faced with the inherent uncertainties of predicting future fish populations -- fisheries managers bend to socio-political pressure to provide jobs and profits for the fishing industry, leading to greater harvests of fish than are prudent," he said. Structurally, fisheries management might be improved by giving commercial fishers a greater vested interest in the long-term health of the fisheries. This could be done by offering them individual transferable quotas or greater involvement in fisheries management. Botsford and colleagues acknowledge that this would be more difficult at the corporate level than in small-scale coastal fishing operations. It would be particularly difficult in international fisheries, where existing institutional structures and cultural differences don't encourage cooperation. The researchers suggest that several changes in the way marine fisheries are managed would improve sustainability, regardless of improvements in marine science. First, they urge adoption of the precautionary approach to fisheries management, which would translate into lower levels of fish harvests unless scientific evidence clearly demonstrates that higher catch rates are warranted. Secondly, Botsford and colleagues suggest establishing marine refuges that are off-limits to fishing in order to protect portions of exploited fish populations and allow those populations to rebuild themselves. And finally, they advocate more liberal use of closures and fishing moratoria to protect declining fish populations or stressed ecosystems before, instead of after, a fish population collapses. The fisheries management study was funded by the Pew Charitable Trust, the Center for Marine Conservation, the U.S. Global Ocean Ecosystems program and Sea Grant.