Faure Johanna, Niol Jasmin, Meheust Eléonore, Spitz Jérôme
Observatoire Pelagis UAR 3462 CNRS - La Rochelle Université La Rochelle France.
Centre D'etudes Biologiques de Chizé (CEBC) UMR 7372 CNRS - La Rochelle Université Villiers-en-Bois France.
Ecol Evol. 2025 Jul 18;15(7):e71815. doi: 10.1002/ece3.71815. eCollection 2025 Jul.
Bycatch (e.g., the accidental capture of non-targeted species by fisheries) is a leading cause of human-induced mortality, contributing to significant population declines worldwide. Often stemming from the overlap between food resources and fishery target species, dietary analysis is key to understanding bycatch patterns. In the Bay of Biscay, common dolphin () bycatch has strongly increased since 2016. Addressing the potential trophic relationship between dolphins and fisheries is essential for developing effective conservation strategies to ensure the sustainability of both dolphin populations and fisheries. Using stomach content analysis, we investigated temporal changes in the occurrence, abundance, and importance by mass of prey between 1999 and 2019. We found no difference in overall diet over time, still composed of pelagic energy-rich prey (pilchards ; horse mackerel spp. and anchovy ). However, we observed a significant decrease in the importance by mass of horse mackerel ( = 2.8365, < 0.01) and an increase in anchovy ( = -4.2636, < 0.01), as well as a decrease in the average size of major species, mainly related to environmental variations in abundance and size distribution of the small pelagic fish. We also identified a shift in minor species from upper slope habitats (e.g., blue whiting ) to species inhabiting coastal waters (e.g., sprat ), reflecting changes in the distribution of common dolphins within the Bay of Biscay. Finally, we highlighted the consistency over time in the prevalence of fresh pilchards and anchovies in the dolphin stomachs, suggesting they are more likely to feed specifically on these species when bycatch occurs. The risk of bycatch may therefore be increased by dolphins targeting pilchards and anchovies in more coastal waters.
兼捕（例如，渔业意外捕获非目标物种）是人为导致死亡的主要原因，致使全球大量种群数量下降。兼捕通常源于食物资源与渔业目标物种之间的重叠，因此饮食分析是了解兼捕模式的关键。自2016年以来，比斯开湾普通海豚的兼捕情况大幅增加。研究海豚与渔业之间潜在的营养关系，对于制定有效的保护策略以确保海豚种群和渔业的可持续性至关重要。我们通过胃内容物分析，研究了1999年至2019年间猎物的出现频率、丰度以及按质量计算的重要性随时间的变化。我们发现总体饮食随时间并无差异，仍由富含能量的中上层猎物（沙丁鱼；竹荚鱼属和凤尾鱼）组成。然而，我们观察到竹荚鱼按质量计算的重要性显著下降（=2.8365，<0.01），凤尾鱼的重要性增加（=-4.2636，<0.01），主要物种的平均尺寸也有所减小，这主要与小型中上层鱼类的丰度和尺寸分布的环境变化有关。我们还发现次要物种从斜坡上层栖息地（如蓝鳕）向栖息在沿海水域的物种（如黍鲱）转变，这反映了比斯开湾内普通海豚分布的变化。最后，我们强调了海豚胃中新鲜沙丁鱼和凤尾鱼出现频率随时间的一致性，这表明在发生兼捕时，它们更有可能专门捕食这些物种。因此，海豚在更多沿海水域以沙丁鱼和凤尾鱼为目标，可能会增加兼捕的风险。
