Christensen, V. 1996. Managing fisheries involving top predator and prey species components.
Reviews in Fish Biology and Fisheries. 6:417-442.

Abstract

Several management strategies for ecosystems with biological interaction are discussed, including predator removal, predator-prey coexistence, prey exploitation, overexploitation, and introduction of sanctuaries. Some case studies related to ecosystem management are briefly presented; these describe Lakes Victoria and Tanganyika, discarding from shrimp trawl fisheries, and the development in the North Sea that led to introduction of multispecies analysis. The concept of "fishing down the food web" is discussed, and the average trophic levels at which the fisheries operate in different ecosystem types are estimated based on quantified trophic flow models. On a global level the fisheries operate around two trophic levels above the primary producers, still one third of the catch of the 70 major fish species caught in the world is of piscivorous fish. Using exploitation-predation rate indices for different ecosystem types, the amount of finfish consumed globally by finfish is very roughly estimated to be three times the catches of finfish. Finally some implications for management of ecosystems are drawn up. Here it is emphasized that it makes little difference if short-term prognoses are based on single-species or multispecies considerations. Multispecies models may however give the better long-term advice, and adaptive management may facilitate the move toward such long-term goals.