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Modern fish communities live fast die young

June 24, 2011 - Washington

A recent study by the Wildlife Conservation Society has found that modern fish communities live fast and die young.

Researchers compared fish recently caught in coastal Kenya with the bones of fish contained in ancient Swahili refuse heaps in order to understand how to rebuild the current fisheries.

According to the study, modern fish communities are not victims of reckless living, but of over fishing which has caused an ecosystem-level transition that may not be easily reversible.

Over the centuries, human fishing has greatly reduced or eliminated larger and longer-lived species that were more commonly caught in the Middle Ages.

The remaining fish communities today contain more species with shorter life spans, faster growth rates, smaller average sizes, and fewer top predators.

The study authors, Tim R. McClanahan and Johnstone O. Omukoto of the Wildlife Conservation Society, utilized more than 5,475 samples of ancient fish remains dating between 1250 and 600 years before the present.

"The ancient Swahili middens represent a time capsule of data, containing information on the composition of the region's fish assemblages and how human communities influenced the marine environment," McClanahan, WCS Senior Conservationist and head of the WCS's coral reef research and conservation program, said.

"The historical data suggest that fishing removes the slower-growing, longer-lived species over time and that marine protected areas are only partially successful in recovering the fish communities of the past," he explained.

The researchers discovered that the life histories of fish caught by modern fisheries and the remains of ancient fish assemblages were significantly different.

"The archaeological evidence demonstrates the incredible longevity of humanity's utilization of coastal fisheries, while emphasizing the critical need to actively manage slower growing, longer-lived species within an ecosystem approach," Dr. Caleb McClennen, Director of WCS's Marine Program, said.

"The evidence from Kenya aligns with findings from around the world that for millennia humanity has relied on the world's oceans for our basic needs-but has more recently failed to do so in a manner that also will sufficiently sustain that resource," he added.

The findings appear in the current online edition of the journal Conservation Biology.


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