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Taking a Second Look at How Marine Reserves are Created

Overfishing has resulted in the serial depletion of fish stocks around the world and caused significant collateral damage to non-target species because of high levels of bycatch. This not only threatens natural marine ecosystems, but also jeopardizes the millions of people who depend on fish for their economic livelihood and dietary protein requirements.

Marine reserve networks—areas of the ocean where fish harvesting is either partially limited or completely prohibited—have been used for years to tackle this issue, and the placement, size, and spacing of these reserves have been primarily based on the dispersal distance of the larvae of the main target species.

However, marine habitats are characterized by rich assemblages of species that interact via competition for resources and predation. Given that the dispersal distance of larvae varies across species, it is unclear how we should design reserve networks to protect entire, interconnected marine communities.

In a paper recently published in Ecological Applications, Northeastern University Prof. Tarik Gouhier shows that current reserve design guidelines derived using single-species models lead to a community-level tradeoff: networks of small and adjacent reserves based on larval dispersal distance simultaneously maximize the abundance of predatory fish and minimize the abundance of their prey, while the converse holds for large and distant reserves. However, reserve networks whose size and spacing is based on the scale of variation of adult fish can simultaneously maximize the abundance of both the predatory fish and their prey. “This theoretical result suggests that the key metric for designing reserves that protect entire communities is not necessarily the dispersal distance of larvae, which varies across species, but the spatial extent of variation in adults.”

Gouhier says he hopes to work with Prof. Jonathan Grabowski, a fisheries expert here at Northeastern University, to test this model prediction in a natural system. “One of the things that attracted me to Northeastern University’s Marine Science Center was the quality of the faculty and the potential to develop collaborative research projects to better understand the response of fragile coastal ecosystems to environmental change.”

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