Scientific surveys are indispensable for understanding fish populations and setting sustainable fishing limits. However, the methods used, particularly bottom trawling and to some extent longlining, can conflict with the conservation goals of marine protected areas (MPAs). As MPAs become more prevalent globally, the debate intensifies over whether such surveys should be permitted within their boundaries, given their potential to disrupt sensitive habitats and species.
This Editor's Choice article from ICES Journal of Marine Science presents a novel approach to address this issue. The authors of the paper developed a method that involves degrading existing survey data to evaluate what abundance indices might look like if surveys were excluded from proposed MPAs. This approach was applied to four groundfish surveys in a proposed MPA network off western Canada, exploring the potential impacts on fish population assessments.
The findings reveal that excluding surveys from MPAs has a relatively minor impact on several groundfish species. However, species with less precise data, those more commonly found within MPAs, or those whose distributions shift in relation to MPAs over time could suffer from biased or uncertain population trends. While redistributing survey efforts outside MPAs can mitigate some precision loss, it risks inaccurately representing population trends.
The study also examines the statistical power to detect significant population declines, showing that the ability to identify large declines over approximately 20 years could be reduced by up to 30 percentage points. This reduction has significant implications for conservation status assessments by various organizations, which often rely on estimated population declines as a critical metric.
The extent of the impact on survey accuracy depends on the proportion of the survey area excluded. With the expected expansion of MPA coverage and other factors like wind farm development and budget constraints potentially limiting survey areas, the integrity of survey indices could be further compromised. While non-destructive survey methods offer some solutions, they require rapid development and calibration against traditional methods to ensure data continuity. These alternatives also fall short of providing necessary biological samples, underscoring the complex trade-offs between conservation objectives and the need for robust scientific monitoring.
This study highlights the need for a nuanced approach to conducting scientific surveys within MPAs, balancing conservation goals with the imperative for accurate marine population monitoring.
