Performance of length-based assessment in predicting small-scale multispecies fishery sustainability

Abstract

Small-scale fisheries play a critical role in food security and contribute to nearly half of reported global fish catches. However, the status of most small-scale fisheries stocks is still poor. In data-limited situations, length-based methods have been widely applied to estimate reference points and to understand stock status. This study applied three different length-based assessment methods (length-based indicators—LBI, length-based spawning potential ratio—LBSPR, and the length-based Bayesian biomass approach—LBB) to predict fisheries stock sustainability in the Azores. Overall, the three methods showed robustness for 15 out of 18 stocks assessed and agreed on their exploitation status. The results showed that 45% of the Azorean stocks were classified as sustainable stocks, 33% possible rebuilding/overfished and 22% overfishing/overfished stock status. Sensitivity analysis showed that biases on the source of initial life-history parameters, especially the asymptotic length (L∞) and the ratio of natural mortality and growth coefficient (M/k), have a stronger influence on the reference points of conservation of mature individuals (LBI), spawning potential ratio and fishing mortality (LBSPR) and the biomass relative to the maximum sustainable yield (LBB). Furthermore, sensitivity analysis indicated that, among the three methods, LBI is more robust. Our findings provide some management recommendations such as (1) catches and effort should be reduced; (2) minimum landing size should be increased; (3) minimum hook size should be increased, to be applied mainly for those stocks classified as possible rebuilding/overfished and overfishing/overfished stock status. Graphical abstract

Tropical fishery nutrient production depends on biomass-based management

“… 90 Although these single-species, length-based indicators are most frequently used in yield per recruit models, we apply them here in the context of community surplus production. 17 , 50 , 91 L mat for each species was obtained directly from the FishLife R package, which uses data found in FishBase and the RAM Legacy Stock Assessment Database to inform a Bayesian model that predicts life history parameters for all finfish species. 61 , 80 , 92 We derived L opt from the life history parameters estimated by FishLife using the equation where L inf is the asymptotic length, M represents natural mortality, and K is the von Bertalanffy growth coefficient.…”

Long-term trends in functional diversity of exploited marine fish in the Azores’ archipelago: past and present

“…Monitoring and quantifying changes in fish communities under exploitation is crucial for effective fisheries management (FAO, 2005;Hilborn et al, 2020;Artetxe-Arrate et al, 2021). Traditionally, fisheries management has primarily relied on species-based approaches, focusing on factors such as species composition, fish size and catches or biomass (Christensen et al, 2014;Froese et al, 2017;Hilborn et al, 2020;Medeiros-Leal et al, 2023). However, concerns about the sustainability of global fisheries have escalated in recent decades, driving researchers and policymakers to actively explore innovative approaches for assessing and managing fish populations (Bradley et al, 2019;Hilborn et al, 2020).…”

“…Fishing in Azorean waters has been recognized as a region with commendable practices that support sustainable fishing practices in small-scale fisheries. This achievement can be attributed, at least in part, to the implementation of diverse local regulations (e.g., area-gear restrictions-Ordinance N°101/2002; fishing effort reduction-Ordinance N°1102-C/2000 and N°43/2009; selectivity restrictions-Ordinance N°101/2002 and N°116/2018, Ordinance N°92/2019) and the establishment of an efficient and unique system for fishery data collection that has been in operation since the 1970s (Pham et al, 2013;Santos et al, 2019;Medeiros-Leal et al, 2023).…”

“…Although significant efforts have been made to manage fishery resources sustainably in the Azores archipelago, there is a growing concern regarding overfishing, ecosystem degradation, biodiversity loss and the impacts of climate change on fisheries (Morato et al, 2006;Morato et al, 2010;Pham et al, 2014;Abecasis et al, 2015;Neves et al, 2021;Torres et al, 2022). This emphasizes the need for a deeper understanding of the changes occurring in fish communities exploited by Azorean fishing fleet (Pham et al, 2013;Fauconnet et al, 2019;Santos et al, 2019;Medeiros-Leal et al, 2023;Parra et al, 2023). To effectively address these concerns, long-term monitoring and new research approaches based on local information are crucial.…”