What is the multispecies approach to fisheries research?

Simply put it is an approach to fisheries research whereby the interactions between and among species and their environment are analyzed. This includes preditor- prey interactions, seasonal variations in distribution, water quality parameters, age, sex, and maturity to name a few. Historically, fishery assessments were (and still are) based on single species models and research. Groups such as the VIMS Juvenile Trawl Survey have been contributing to single species research for over 40 years by providing juvenile indices of commercially important species in the Chesapeake Bay.

The single species approach looks at a single stock as if it is an independent entity in the ecosystem, unaffected by other processes and having no effect on other species. Management decisions take into account fishing and natural mortality, juvenile indices, and expected recruitment to the fishery. Fishing rates are then set for the target species. The regulations established based on single species models may have strong relationships with other species. If you remove more of a species such as menhaden because the model indicates a high population, will it have an affect on its predators, such as striped bass and weakfish? Will their populations also decline? What if the menhaden recruitment fails? Will it effect other species as well? Questions such as these have led to a desire to shift fishery management approaches.

Around the world scientists and fisheries managers are realizing that a single species approach is not enough. The push to move to ecosystem based management (this is the term that has been adopted by many groups to describe multispecies management in broader detail)has been gaining momentum. Before any management decisions can be made based on this concept the basic information available needs to be assessed and understood. In most cases the information needed simply does not exist and is very difficult to obtain.

Historical data on commercially important species for certain parameters such as biomass, landings and length frequencies are available to a limited degree, however they are far from sufficient to describe a multispecies model. To gather the information needed, fishery independent research will need to be done and maintained for all species in the target ecosystem(the Chesapeake Bay). The requirements for this type of survey are explained in the pages discussing Sampling Design and Modeling Requirements.