The goal of this symposium is to gather worldwide expertise and discuss how to incorporate ecosystem considerations into practical fishery management advice, and to recommend a process for advancing fishery management beyond the single species model.
In the last 10 years, there has been a growing perception that it is not effective to base fisheries management policies solely on single-species considerations. Large decadal shifts in species composition, abundance, and productivity are common, and are not predictable from single-species models. Climate regime shifts and human activities (e.g., overfishing, pollution, habitat degradation) are implicated in these changes.
North American examples include (1) Georges Bank, where the bottomfish community, once dominated by commercially valuable species such as cod and haddock, shifted to lower-valued species such as skates and dogfish; and (2) Gulf of Alaska and Bering Sea, where declines of crabs and shrimps have given rise to increasing pollock and flatfish. Severe economic hardships are associated with such declines in commercial fisheries.
Beyond consumer preferences, society places high values on marine ecosystem components, such as marine mammals, seabirds, and turtles. Threatened or endangered species warrant special consideration. Population declines often lead to after-the-fact adjustments to fishing regulations without a good understanding of cause and effect. Is it therefore desirable to incorporate ecosystem considerations into fishery management advice?
It may be argued that objectives for optimal yields are best met by applying harvest rate specifications, while no useful objectives exist for incorporating ecosystem considerations in fishery management. It may also be argued that objectives for simultaneous optimal yields from all fisheries are simply impossible, and that fishery management objectives need to be restated with a more holistic view of ecosystem processes.
Although well-established methods exist to apply stock assessments and biological reference points, further progress must be made if ecosystem considerations are to result in tangible fishery management advice.
Ecosystem processes also include the effects of nutrient additions from fish carcasses which have been identified in estuaries and in anadromous lakes and streams. Consideration of these effects on long-term ecosystem productivity may affect the harvest management of these species.