Fisheries Impacts on North Atlantic Ecosystems: Evaluations and Policy Exploration
Estimating Illegal and Unreported Catches from Marine Ecosystems: Two Case Studies
Estimating Illegal and Unreported Catches from Marine Ecosystems: Two Case Studies
Robyn Forrest, Tony Pitcher, Reg Watson Hreiðar Þór Valtýsson and Sylvie GuénetteAbstract
Estimation of total harvests of marine organisms is essential if true impacts of fisheries are to be evaluated. Such estimates are difficult to obtain because, for many of the world's fisheries, an unknown proportion of the catch is not reported. Components of the unreported catch may include discards, deliberately misreported catch and unmandated catch (catch that it is not required to be reported). For many fisheries, estimates of misreporting or discarding exist, but may not apply to all periods of interest. Here we demonstrate a methodology for estimating unreported catches over time, based on knowledge of factors that influence misreporting in the fishery and on independent (published and unpublished) estimates of misreporting. Independent estimates and knowledge of influence factors are combined to assign quantitative estimates of misreporting to different periods so that time-series of misreporting can be obtained. The method is demonstrated for two national fisheries: Iceland and Morocco. The Icelandic analysis is a by-species approach for cod and haddock. The Moroccan analysis divides catches into demersal and pelagic categories, rather than individual species. Preliminary results suggest that Icelandic cod catches may have been underestimated by between 1% and 14% at different times, and haddock catches by between 1% and 28%. Underestimation of Moroccan catches appears to have been by as much as half in some cases. Uncertainty has been incorporated into our analyses by using multiple sources of information to provide upper and lower estimates of misreporting and by using a Monte Carlo simulation. These case studies show that it is possible to obtain some estimate of misreporting, even when rigorous data are lacking. Sources of information are presented so that areas where information is lacking are easily identified, offering a basis for comment, discussion and, it is hoped, collaboration that will lead to provision of further information and improvement of the estimates.