Instituto Português do Mar e da Atmosfera, IPMA, Estação Piloto de Piscicultura de Olhão, Avenida 5 de Outubro, s/n, 8700-305 Olhão, Portugal.
J Fish Biol. 2013 Sep;83(3):480-500. doi: 10.1111/jfb.12184. Epub 2013 Aug 7.
The behavioural effects of confinement of sardine Sardina pilchardus in a purse seine were evaluated through three laboratory experiments simulating the final stages of purse seining; the process of slipping (deliberately allowing fishes to escape) and subsequent exposure to potential predators. Effects of holding time (the time S. pilchardus were held or entangled in the simulation apparatus) and S. pilchardus density were investigated. Experiment 1 compared the effect of a mild fishing stressor (20 min in the net and low S. pilchardus density) with a control (fishing not simulated) while the second and third experiments compared the mild stressor with a severe stressor (40 min in the net and high S. pilchardus density). In all cases, sea bass Dicentrarchus labrax were used as potential predators. Results indicated a significant effect of crowding time and density on the survival and behaviour of slipped S. pilchardus. After simulated fishing, S. pilchardus showed significant behavioural changes including lower swimming speed, closer approaches to predators and higher nearest-neighbour distances (wider school area) than controls, regardless of stressor severity. These results suggest that, in addition to the delayed and unobserved mortality caused by factors related to fishing operations, slipped pelagic fishes can suffer behavioural impairments that may increase vulnerability to predation. Possible sub-lethal effects of behavioural impairment on fitness are discussed, with suggestions on how stock assessment might be modified to account for both unobserved mortality and sub-lethal effects, and possible approaches to provide better estimates of unobserved mortality in the field are provided.
通过三个模拟围网作业最后阶段的实验室实验，评估了沙丁鱼（Sardina pilchardus）在围网中被禁闭的行为影响；这些阶段包括滑溜（故意让鱼逃脱）和随后暴露于潜在捕食者的过程。实验研究了持鱼时间（沙丁鱼在模拟装置中被持留或缠绕的时间）和沙丁鱼密度的影响。实验 1 比较了轻度渔业胁迫（在网中 20 分钟且沙丁鱼密度较低）与对照组（未模拟捕捞）的影响，而第二和第三实验则将轻度胁迫与重度胁迫（在网中 40 分钟且沙丁鱼密度较高）进行了比较。在所有情况下，都使用鲈鱼（Dicentrarchus labrax）作为潜在捕食者。结果表明，拥挤时间和密度对逃脱的沙丁鱼的存活和行为有显著影响。经过模拟捕捞后，与对照组相比，沙丁鱼表现出明显的行为变化，包括游泳速度降低、更接近捕食者以及最近邻距离（更宽的鱼群区域）增加，而不论胁迫严重程度如何。这些结果表明，除了与渔业操作相关的因素导致的延迟和未观察到的死亡率之外，逃脱的洄游性鱼类可能会遭受行为障碍，从而增加被捕食的脆弱性。讨论了行为障碍对适应性的潜在亚致死影响，并就如何修改种群评估以同时考虑未观察到的死亡率和亚致死影响提出了建议，并提供了在现场提供更好的未观察到的死亡率估计的可能方法。
