Main content area

Trophic cascades triggered by overfishing reveal possible mechanisms of ecosystem regime shifts

Daskalov, Georgi M., Grishin, Alexander N., Rodionov, Sergei, Mihneva, Vesselina
Proceedings of the National Academy of Sciences of the United States of America 2007 v.104 no.25 pp. 10518-10523
Mnemiopsis leidyi, anthropogenic activities, ecosystem management, ecosystems, eutrophication, fisheries management, humans, introduced species, models, overfishing, predators, Black Sea
Large-scale transitions between alternative states in ecosystems are known as regime shifts. Once described as healthy and dominated by various marine predators, the Black Sea ecosystem by the late 20th century had experienced anthropogenic impacts such as heavy fishing, cultural eutrophication, and invasions by alien species. We studied changes related to these "natural experiments" to reveal the mechanisms of regime shifts. Two major shifts were detected, the first related to a depletion of marine predators and the second to an outburst of the alien comb jelly Mnemiopsis leidyi; both shifts were triggered by intense fishing resulting in system-wide trophic cascades. The complex nature of ecosystem responses to human activities calls for more elaborate approaches than currently provided by traditional environmental and fisheries management. This implies challenging existing practices and implementing explanatory models of ecosystem interactions that can better reconcile conservation and ecosystem management ideals.