Mexico is among the world’s 20 leading fish producers, but 57% of the nation's fisheries are fully exploited and 25% are over-exploited. Overexploitation is especially evident in the Gulf of California, Mexico's main supplier of fishery resources. Since the 1990's, Mexico has implemented structural changes in fisheries management and policy that are congruent to the relevant status of the fisheries, but the prevalence of illegal fishing, non-compliance and enforcement problems make it difficult to evaluate the effect of these policies on fisheries and the marine ecosystem. We identified the effects of current fishery management strategies for the marine system of the Northern Gulf of California (above 28º N), Mexico, using Atlantis, a spatially-explicit ecosystem model. This methodology is a modeling approach within the Integrated Ecosystem Assessment (IEA) framework, and is intended as a strategic tool to test alternative management strategies. We used the Atlantis Ecosystem Model to simulate the status quo, exemplified by the current levels of catch and partial compliance with existing regulations. We then simulated a scenario where all existing regulations are followed.
Results/Conclusions
We identified these regulations as spatial restrictions (i.e. Natural Protected Areas); restrictions on catch, gears, seasonal closures, and size limits for 16 fisheries; and programs for reduction of effort and impact of fisheries (i.e. buyout, rentout and effort reduction programs). We evaluated the effects on potential harvest and food web structure using a variety of ecosystem indicators, such as ratios of functional groups and mean trophic level. We found that the ratios of abundance of functional groups showed shifts in community structure as levels of harvest increased. Our results predict that status quo fisheries might lead to continued declines in ecological condition and economic performance over the next 20 years. On the other hand, full enforcement of existing regulations would lead to improved long term ecological and economic outputs, and in most cases would keep fish stocks and fisheries at target levels. These results suggest that increased enforcement and implementation of existing policies can have a positive effect on the ecosystem function.
