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Overfishing, fish extinctions can alter nutrient recycling

Tropical fish species that are major targets of fisheries also play important roles in aquatic nutrient cycling, and their loss due to overfishing could have detrimental effects on ecosystems, researchers report. Michael Vanni (zoology) is among the authors of the study published in the Proceedings of the National Academy of Sciences Feb. 20.

The abundance and diversity of fish in tropical waters make them key components of the food web — actions that threaten this species richness, such as overfishing or habitat alteration, may have profound consequences.

The study provides a quantitative assessment of the effects of fish extinctions on ecosystem functioning. The researchers assessed how species extinctions might alter one key role of fish: the recycling of the essential nutrients nitrogen and phosphorus. They first estimated the contributions of nitrogen and phosphorous recycling for each fish species at two tropical sites, Rio Las Marias in Venezuela and Africa’s Lake Tanganyika. Then they ran numerical simulations to assess the potential consequences of extinctions for nutrient recycling by fish.

Notably, the sharpest declines in nutrient recycling occurred when the extinctions were based on actual patterns of fishing pressure recorded by the team. The authors conclude that fisheries target species whose combination of large body size and high population density makes them important in nutrient recycling. Loss of such species could potentially compromise the productivity of the entire ecosystem by altering nutrient cycling.

Date Published: 03/08/2007
Volume: 26   Number: 16


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