Data from: Hidden demographic impacts of fishing and environmental drivers of fecundity in a sea turtle population

Fisheries bycatch is a critical threat to sea turtle populations worldwide, particularly because turtles are vulnerable to multiple gear types. The Canary Current is an intensely fished region, yet there has been no demographic assessment integrating bycatch and population management information of the globally significant Cabo Verde loggerhead turtle (Caretta caretta) population. Using Boa Vista island (Eastern Cabo Verde) subpopulation data from capture-recapture and nest monitoring (2013–2019), we evaluated population viability and estimated regional bycatch rates (2016–2020) in longline, trawl, purse-seine, and artisanal fisheries. We further evaluated current nesting trends in the context of bycatch estimates, existing hatchery conservation measures, and environmental (net primary productivity) variability in turtle foraging grounds. We projected that current bycatch mortality rates would lead to the near extinction of the Boa Vista subpopulation. Bycatch reduction in longline fisheries and all fisheries combined would increase finite population growth rate by 1.76% and 1.95%, respectively. Hatchery conservation increased hatchling production and reduced extinction risk, but alone it could not achieve population growth. Short-term increases in nest counts (2013–2021), putatively driven by temporary increases in net primary productivity, may be masking ongoing long-term population declines. When fecundity was linked to net primary productivity, our hindcast models simultaneously predicted these opposing long-term and short-term trends. Consequently, our results showed conservation management must diversify from land-based management. The masking effect we found has broad-reaching implications for monitoring sea turtle populations worldwide, demonstrating the importance of directly estimating adult survival and that nest counts might inadequately reflect underlying population trends.

渔业副渔获物（fisheries bycatch）是全球海龟种群面临的核心威胁，尤为关键的是，海龟对多种渔具类型均具有较高的易感性。加那利海流（Canary Current）是捕捞强度极高的海域，但目前尚未开展针对具有全球重要性的佛得角蠵龟（Caretta caretta）种群、整合副渔获物与种群管理信息的种群评估。本研究依托2013—2019年佛得角东部博阿维斯塔岛亚种群的标记重捕（capture-recapture）与巢穴监测数据，对该亚种群的生存力进行了评估，并估算了2016—2020年延绳钓、拖网、围网及小型手工渔业的区域副渔获率。我们进一步结合副渔获物估算结果、现有孵化场保育措施，以及海龟觅食场的净初级生产力（net primary productivity）变化，评估了当前的巢穴种群趋势。研究预测，当前的副渔获死亡率将导致博阿维斯塔岛亚种群濒临灭绝。仅降低延绳钓渔业副渔获量，以及全面降低所有渔业的副渔获量，分别可使种群有限增长率提升1.76%与1.95%。孵化场保育措施可提高幼龟孵化产量并降低灭绝风险，但单独实施无法实现种群增长。2013—2021年巢穴数量的短期上升，推测由净初级生产力的临时提升驱动，可能掩盖了长期持续的种群衰退趋势。当繁殖力与净初级生产力关联时，我们的后报模型（hindcast models）可同时复现这种长期与短期的对立趋势。综上，本研究结果表明，海龟保育管理需脱离单一的陆地管理模式，转向多元化策略。本次发现的掩盖效应对全球海龟种群监测具有广泛的借鉴意义，证实了直接估算成体存活率的重要性，同时也表明巢穴数量可能无法充分反映种群的真实变化趋势。