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Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, and Future Options
Fisheries management strategies currently employed in the United States generally do not take into account ecosystem effects and multi-species interactions. Ecosystem considerations are discussed in regular stock assessments, but in general they do not involve a comprehensive evaluation of management strategies. Also, environmental impact statements are required for major fishery management actions, but there is no regulatory requirement to account for interactions among species. Instead, harvest policies tend to focus almost exclusively on single species, and maximum sustainable yield reference points are the norm.
In a multi-species context, interaction between species, mediated through predator-prey interactions and food-web effects, will need to be explicitly considered when deciding harvest strategies. For examples, if interacting species are both targeted for harvest, maximizing yield for each will likely be impossible. Tradeoffs between the allowable catch of each species will need to be made, and the desired level for each species’ harvest decided simultaneously. This must occur while avoiding possible undesirable and irreversible shifts in the composition of the overall ecosystem. In addition, fisheries are not the only service that humans derive from the ocean, and incorporating these values into fisheries management decisions further increases the apparent number of tradeoffs.
Protecting ecosystem functioning and making allocation decisions between uses are two distinct—yet interdependent—issues that managers will have to face with increasing frequency as ecosystem considerations are factored into fisheries management. Within a functioning ecosystem, differing harvest and protection goals can be established amidst a variety of stewardship options and tradeoffs between uses. Greater understanding of these tradeoffs and the consequences of management actions are needed, but ultimately, society will need to decide the desired balance of services provided by the ocean and what protections to afford marine species. Based on these decisions, management approaches will need to be crafted to increase the chances that harvest controls are implemented effectively and in a manner that might further ecosystem considerations among users.
The following recommendations fall into three categories: (1) implementing ecosystem considerations in fisheries management actions, (2) promoting stewardship, and (3) supporting future research.
Applying a Food-Web Perspective to Fishery Management Strategies
Multiple-species harvest strategies should be evaluated to account for species interactions and food-web dynamics.
Setting multi-species harvest strategies requires taking into account food-web interactions, changes in trophic structure, life history strategies, and bycatch,