June 26, 2011

Modern Fish Communities Live Fast, Die Young

Fish communities in the 21st Century live fast and die young. That's the main finding of a recent study by researchers from the Wildlife Conservation Society who 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.


The study"”which utilized more than 5,475 samples of ancient fish remains dating between 1250 and 600 years before the present (approximately AD 750"”1400)"”appears in the current online edition of the journal Conservation Biology. The authors are Tim R. McClanahan and Johnstone O. Omukoto of the Wildlife Conservation Society.

"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," said McClanahan, WCS Senior Conservationist and head of the WCS's coral reef research and conservation program. "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."


The researchers discovered that the life histories of fish caught by modern fisheries and the remains of ancient fish assemblages were significantly different. Whereas ancient fish communities had a high percentage of top predators"”species that prey on fish and large invertebrates such as snails, sea urchins, and clams"”modern fish communities contain more species that feed on plants, small invertebrates like sea lice, generally smaller species that feed lower on the food chain. Modern fish assemblages also contain more species that are smaller in size with higher growth and mortality rates.


"The archeological 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," said Dr. Caleb McClennen, Director of WCS's Marine Program. "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."



Image Caption: The Wildlife Conservation Society compared the remains of fish from ancient Swahili refuse heaps in Kenya with data from recently caught fish to understand how fish communities there have changed over time. The finding: fishing pressures have greatly reduced the percentage of longer-lived, slower growing species such as the lined surgeonfish. Credit: T. McClanahan/Wildlife Conservation Society


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