Effect of Marine Reserves on Cod and Haddock Population Dynamics: Application of GLOBEC Results to Ecosystem Management

J. Hare (NOAA), M. Fogarty (NEFSC), D. Mountain (NEFSC), F. Werner (UNC), P. Sullivan (Cornell) and A. Yakubu (Howard)

This proposed work will address critical issues in the development of ecosystem-based approaches to fisheries management through the application of data, models, and knowledge derived during the Northwest Atlantic/Georges Bank GLOBEC Program (NWA/GB GLOBEC). Specifically, we propose to combine NWA/GB GLOBEC data and models with extensive survey data and population dynamics models to address the effect of marine reserves on cod and haddock populations in the northeast U.S. continental shelf ecosystem. Marine reserves confer two general benefits to exploited populations. 1) Fishing mortality is near zero in reserves resulting in increases in fish biomass and size-structure. Fisheries then benefit when these individuals move across the reserve boundary and enter fished areas (termed 'spillover'). 2) The increases in biomass and size result in increased reproductive output of the local population in the reserve. In turn, more eggs lead to increased recruitment, possibly both inside and outside of the reserve (termed 'larval export'). Although this second benefit is potentially more important than the first, there are very few studies that document the 'larval export' effect. Further, there is little information about the interaction between adult 'spillover' and 'larval export' ? greater 'spillover' implies less increase in biomass, which would limit 'larval export'.

In 1994, several year-round fishery closure areas were established on Georges Bank. These areas are one of the largest systems of 'marine reserves' now in effect. The closed areas dramatically altered the spatial distribution of fishing on Georges Bank, and with concomitant reductions in overall fishing effort, dramatically changed fishing mortality. Subsequently, the biomass of commercial fish species on Georges Bank increased, and large year-classes of haddock (2003) and possibly of cod (2004) occurred. Yet, the role of the reserves in generating these increases in biomass and large year-classes is uncertain. The relative effects of reserves and overall fishing effort have not been assessed. Further, marine reserves have not been considered in the context of environmentally-driven or climatically-driven variability in recruitment. Finally, the importance of local population dynamics acting on scales smaller than currently defined stocks is unknown. These issues identify a major question facing the development of ecosystem approaches to fisheries management ? what is the role of marine reserves as a tool to build and conserve sustainable fisheries in the context of other 'real-world' factors affecting the population dynamics of exploited species?

The NWA/GB GLOBEC Program targets a productive ocean ecosystem that supports culturally and economically valuable fisheries. The Program's emphasis is on understanding the relationship between zooplankton and climate change, and links to fisheries through larval fish transport and trophodynamics. Research efforts included broad- and process-scale surveys of zoo- and ichthyoplankton, collection of physical oceanographic data, and the development of fine- scale 3-D circulation models. These detailed data are against the back-drop of 30-40 years of ecosystem and fisheries data collected by government agencies. We will combine the results of NWA/GB GLOBEC with this long-term survey data and population dynamic models used by fisheries scientists to develop a spatially-explicit, stagestructured population model of cod and haddock in the ecosystem. We will then examine the effects of closed areas, fishing effort, environmental variability, and local populations on the dynamics of these populations. When completed, we will achieve four important results: 1) advance the basic understanding of the role of marine reserves in fisheries management, 2) provide specific information and models to improve NOAA's management of ecosystems, 3) assess the importance of spatial processes in the dynamics of fishery species, and 4) evaluate the effect of climate change on cod and haddock populations.

The scientific results of this project and the training of graduate students and post-docs at both government laboratories and universities will ensure that the results of the U.S. GLOBEC Program are directly applied to the development of ecosystem approached to fisheries management.