Detrimental genetic effects of interactions between reared strains and wild populations of marine and anadromous fish and invertebrate species

Cultured strains of marine and anadromous species reared for aquaculture can be either inadvertently (as in farm escapes) or deliberately (as in stocking/ranching) introduced into the wild, where they may interact with wild conspecifics or other species. This chapter concentrates on the potentially detrimental genetic aspects of these interactions, largely in the context of species cultured in Europe but considering general principles, which have worldwide applicability. Most previous experimental work in the area has involved Atlantic salmon, which has the highest production of any finfish produced in Europe. These investigations have shown generally detrimental results for wild salmon populations, when interactions occur with reared strains. The various European species which might be affected by cultured introgressions (the major aquaculture species) are then considered under several headings: genetic composition of cultured strains compared with wild populations; modes of introduction into the wild; direct and indirect genetic interactions with wild populations/species; consequences of such interactions; establishing the severity of effects of wild/reared interactions with different species, utilising opportunist situations and field experiments; and, methods such as induction of sterility in reared strains to reduce detrimental effects. Relative risks for wild populations of the major aquaculture species are then considered, and general and specific genetic recommendations are presented.