The current global crisis in marine capture fisheries contrasts sharply with the recovery of some stocks of marine mammals. Eventually this will have to lead to a re-evaluation of the preferential treatment that marine mammals now often enjoy. The widening support for ecosystem-based fisheries management (EBFM) and the growing insight in the interactions between marine mammals and commercial fisheries are expected to influence this evaluation. This article examines the role of marine mammals in the ecosystem with special emphasis on predation on commercial fisheries. Ample attention is devoted to the definition of EBFM, its legal status and issues of implementation. The 2001 Reykjavik Declaration on Responsible Fisheries in the Marine Ecosystem is used for illustration. One of the conclusions is that sufficient scientific research is required to substantiate positive effects that pre-emptive catches of marine mammals would have for (recovering) commercial fisheries. The regulatory objectives and international legal constraints relevant to marine mammals are moreover addressed to determine if the exploitation of marine mammals could be obligatory or "necessary".