The potential of marine reserves for the management of northern cod in Newfoundland
Abstract:Marine reserves (areas closed to exploitation of marine life) should allow better resilience to management errors such as overestimation of stocks, inadequate control of fishing effort, and inaccurate catch statistics. We employed a detailed population model to explore the use of marine reserves to protect cod populations from overexploitation. The northern cod of the east coast of Newfoundland in the 1980s, at low biomass but prior to the major collapse, was used as a case study. We asked two questions: Would marine reserves have prevented the 1992 collapse, and how would reserves compare with other management measures? The model is age- and spatially-structured and includes a recruitment function (Beverton and Holt type). Migrations were simulated by inclusion of target cells (attraction sites), which were specific for each age and month of the year. Random movements around target cells determined how fish spread to form a spatial distribution that moved along the seasonal trajectory defined by the target cells. Fishing was calibrated from historical data on temporal and spatial distribution of effort for three types of gears (trawl, gill net, trap). Marine reserves were modeled alone or in conjunction with temporal closures. For the 1980s low cod biomass, if used alone, only large reserves (80% of the fishing grounds) would have prevented the collapse and allowed the cod stock to rebuild. However, these very large reserves would have reduced the catch per unit effort on the remaining fishing grounds and possibly triggered an increase in investment in gear, defeating the purpose of the reserve. At low cod biomass, reserves must be accompanied by a reduction in fishing capacity. When used with reserves of moderate size (20%), temporal closures to trawls and gill nets succeeded in preventing a collapse and rebuilding the stock.
Document Type: Research Article
Publication date: 2000-05-01
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