Competition with Fisheries
Fisheries also have a major, albeit difficult to quantify, indirect impact on cetaceans. Most whales and dolphins feed opportunistically on a variety of fish and cephalopod species. However, schooling fish, such as herring, mackerel and sand eel, are often preferred prey. Over-exploitation of fish stocks and their subsequent dramatic declines impose major threats to marine predators dependent upon them for food. Such a reduction in prey availability may be seen as a form of habitat degradation.
In fact, most of the cetacean species commonly occurring in the Agreement Area (short-beaked common dolphin, bottlenose dolphin, harbour porpoise, killer whale, Atlantic white-sided dolphin and white-beaked dolphin) are vulnerable to prey depletion. This is especially true for populations with restricted or localized coastal distributions (see e.g. Perrin, Würsig & Thewissen (Eds.) 2009. Encyclopaedia of Marine Mammals. Second Edition). Shifts in diet corresponding to a decline in abundance of preferred fish species have e.g. been observed in harbour porpoises in Scottish waters and the southern North Sea and in other parts of the world outside of the ASCOBANS Area.
The commercial fisheries in the ASCOBANS area fall within the responsibility of the European Union (EU – DG Mare) and the North East Atlantic Fisheries Commission (NEAFC). NEAFC’s main fisheries target redfish, mackerel, haddock, herring, blue whiting and deep-sea species. EU fishing quotas and TACs (total allowable catch) are set by the European Commission. Both receive advice from the International Council for the Exploration of the Sea (ICES), a scientific and research organization. In order to address the problem of prey depletion, ASCOBANS seeks to cooperate with the European Commission as well as other relevant regional agreements, such as OSPAR and HELCOM.