Out of the frying pan, into the fire? Potential trade-offs in managing Pacific rockfish.
Harvey, Chris*,1, Gross, Kevin2, Simon, Victor1, Agostini, Vera3, 1 Northwest Fisheriers Science Center, Seattle, WA, USA2 North Carolina State University, Raleigh, NC, USA3 University of Washington, Seattle, WA, USA
ABSTRACT- There are increasing calls for an ecosystem approach to fisheries management, wherein ecological interactions and dynamics of target species are explicitly incorporated into decision-making. Implementing this approach involves understanding and anticipating potential tradeoffs in multi-species fisheries. For example, there are cases in which multiple species are captured in the same fishery and are also directly linked by ecological interactions such as predation; in such cases, management decisions directed at one species may have unforeseen feedbacks on the other species, according to the strength of their interactions. In this study, we examine the dynamics of overfished rockfish (genus Sebastes) and the commercially important Pacific hake (Merluccius productus) on the west coast of North America. The hake fishery is often closed because of bycatch of rockfish; however, hake also feed on juvenile rockfish. We evaluated the importance of bycatch mortality vs. predation mortality on rockfish using 2-species population models. We identified circumstances under which ceasing hake fishing to stop bycatch of adult rockfish actually had a negative effect on rockfish population growth rate because of greater hake predation on rockfish juveniles, although the conditions under which this tradeoff occurred depended on rockfish life history characteristics, hake recruitment dynamics, and spatial distribution of hake as a function of climate. Our results highlight the need for integrating ecological interactions into stock assessments and management decisions, and also identify key data gaps that will help resolve where and when this tradeoff occurs.
Key words: rockfish, fisheries management, predator-prey interactions, depensatory mortality
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