Effects of Bias in Fisheries Monitoring

This technical report illustrates the effects of bias in independent monitoring of fisheries, specifically focusing on the accuracy of catch estimates. The study employs a computer simulation of a hypothetical longline tuna fleet to assess how different monitoring and review strategies impact the reliability of catch data. It outlines various scenarios for monitoring coverage and data review rates, emphasizing the importance of comprehensive independent monitoring to mitigate bias. The report details that when monitoring coverage is less than 100%, there is a risk of opt-in bias, leading to underestimates of catch rates and potentially skewing data on market and bycatch species populations. The findings advocate for regional fisheries management organizations to implement guidelines for 100% independent monitoring and random review of fishing activities to enhance the credibility of catch estimates and support sustainable fisheries management. The report includes a discussion on the implications of biased monitoring for fisheries management and sustainability goals.