Overfishing the World's Inland Waters a Neglected Crisis

COLLEGE STATION, Texas, December 1, 2005 (ENS) - Fish pulled from the world's lakes and rivers is not the endless source of food, jobs and income that it once appeared to be,according to according to new research from Texas A&M University. Overexploitation of one species after another is rapidly threatening biodiversity and balance of inland water ecosystems worldwide.

"Overfishing of inland waters is a neglected crisis," said Dr. Kirk Winemiller, Texas Agricultural Experiment Station fish researcher, who led the research study published in the December issue of "BioScience." Too little attention is paid to the problem, Winemiller said.

The total catch may remain high, Winemiller and his team have found, but invidual species are disappearing. As one species is depleted, the next species is targeted by fishermen. "So, the overall catch appears stable while biodiversity declines until a point of collapse may be reached," he explained.

Winemiller studied the issue of decreasing inland fish numbers with J. David Allan, University of Michigan; Robin Abell, World Wildlife Fund in Washington, DC; Zeb Hogan, University of Wisconsin; Carmen Revenga, The Nature Conservancy; Brad Taylor, University of Wyoming; and Robin Welcomme of the Long Barn in Suffolk, England.

The team said it will take local people working with fisheries experts to develop plans to co-manage the "critically harvested" bodies of water.


Professor Kirk Minemiller examines fish in a market in the African country of Mali. (Photo courtesy Texas A&M)
But the team recognizes that ecosystem based fisheries management may be long in developing. Although many studies have documented over-fishing to be a major cause of the decline of global fisheries, most of the focus is on oceans.

Inland waters are rarely mentioned because not enough information has been gathered about these fisheries, Winemiller said. Yet, he said, fish from inland waters are more threatened than those in oceans.

Many factors overlap and intertwine to threaten inland waters.

"Tens of millions of people in developing countries fish inland waters for food and to earn a living," Winemiller said. "Typically, fishing pressure shifts from species to species as preferred types or those more easily captured decline in number.

The researchers found that the total catch from inland waters was about 8.7 million metric tons in 2002, the last year for which numbers are available, and that does not include recreational fishing or fishing from aquaculture farms. Sixty-five percent was from Asia, the report indicates.

Overall harvest from the world's lakes and rivers has quadrupled since 1950, when data collection first began by the United Nations Food and Agriculture Organization (FAO).

Among the critically endangered fish cited in case studies by the team are the Mekong giant catfish of the Mekong River basin in Cambodia and the Murray cod of the Murray River basin in Australia.

The lake sturgeon of the Saint Lawrence River and Great Lakes between Canada and the U.S. is noted as currently vulnerable.

Commercial fishing in rivers and lakes is not as intense in North America as it is in many other parts of the world, Winemiller said. "Nonetheless, the increase in recreational fishing may be having a huge impact on fish numbers though poundage of harvest is generally not reported."

The FAO estimates about two million metric tons are taken from inland waters in the world every year. Research shows that reductions of some of these species can profoundly affect productivity and other ecological attributes of freshwater ecosystems, Winemiller said.

The Winemiller Lab at Texas A&M investigates community ecology, fish ecology, fish evolution, and ecosystem ecology in freshwater and estuarine habitats.

The research is field oriented, with studies conducted at sites throughout Texas, Latin America, and Africa. Field research adopts descriptive, comparative and experimental approaches to investigate fish reproduction and life history strategies, feeding ecology, habitat use, species interactions, and food web ecology.

"Managing fisheries today is not limited to just satisfying the commercial fishing industry," the research team says, "but must accommodate the wide array of economic and social benefits that people derive from freshwater ecosystems, including food security and economic growth."