Discards - Impacts

Impacts

Discarding impacts on the environment in two ways; firstly, through increased mortality to target and non-target species, particularly at juvenile life-history stages, and secondly, through alteration of food webs by supplying increased levels of food to scavenging organisms on the sea floor, and to sea birds. The survival of discarded fish and invertebrates is variable and depends on species and fishing gear used. For example, species such as the Pacific halibut caught in long-line fisheries in the Bering Sea, or lesser spotted dogfish in beam trawls in the English Channel have survival rates of between 88-98%. Survival rates of roundfish discards are significantly lower, and this mortality is included in most ICES stock assessments. Crustaceans are thought to be more hardy, though survival of crustaceans is variable; for instance, a survival rate of 25% is assumed for Nephrops norvegicus, the Norway Lobster, whilst survival rates of almost 100% have been demonstrated for the hermit crab, Pagurus bernhardus.