Data from: Effects of seal predation on a modelled marine fish community and consequences for a commercial fishery

We constructed a size- and trait-based dynamic marine community model of the Celtic Sea/Biologically Sensitive Area, including grey seals Halichoerus grypus (Fabricius 1791) and harbour seals Phoca vitulina vitulina (Linnaeus 1758) to examine potential resource conflict between seals and commercial trawl fisheries. The model incorporates seal diet preference, population size and commercial fishery catch, with survey data to quantify ecological interactions between seals and fisheries. Total annual consumption by seals was an order of magnitude less than the catch of the modelled trawl fishery. Increasing fishing pressure reduced fish spawning stock biomass (SSB) much more than a proportionally equivalent increase in seal predation. For most fish species, quadrupling seal predation showed little effect on the predicted fishery catch.
These results arise from relatively low seal abundance and partial niche partitioning. The fishery harvested a wider range of fish lengths and species than seals consumed. The fish community was dominated by small fish lengths and seals predated on these more than suggested by their calculated diet preference. Seal predation disproportionately affected several fish species not targeted by the fishery, but seal predation did not significantly affect the SSB of any of the species that constitute 90% of the total landings of the fishery. Synthesis and applications. Predation of fish by grey and harbour seals is unlikely to harm commercial trawl fisheries in south-west Irish waters. This conclusion differs from those of some model-based studies of other North Atlantic systems, demonstrating the need for ecosystem-specific evidence in considering such conflicts. In systems with low niche overlap between seals and fisheries, the two are largely decoupled in effect, leaving fishing pressure as the overwhelming determinant of targeted fish stock status.

本研究构建了基于体型与功能性状的凯尔特海/生物敏感区动态海洋群落模型，纳入灰海豹（学名：*Halichoerus grypus*，Fabricius 1791）与港海豹指名亚种（学名：*Phoca vitulina vitulina*，Linnaeus 1758），用以探究海豹与商业拖网渔业间潜在的资源冲突。该模型整合了海豹食性偏好、种群规模与商业渔业捕捞量，并结合调查数据量化海豹与渔业间的生态相互作用。海豹年度总摄食量较模型中拖网渔业的捕捞量低一个数量级。捕捞压力提升对鱼类产卵群体生物量（SSB）的负面影响，远大于海豹捕食率按比例同等提升所带来的影响。对于多数鱼类而言，将海豹捕食量提升至原有的4倍时，对预测的渔业捕捞量几乎无影响。上述结果源于海豹种群丰度较低，且二者存在部分生态位分化。相较于海豹的摄食对象，渔业捕捞覆盖了更广的体长范围与更多种类的鱼类。鱼类群落以小型个体为主，而海豹对小型鱼类的捕食量高于其食性偏好的计算结果。海豹捕食对若干渔业非目标鱼类产生了不成比例的影响，但并未对占渔业总捕捞量90%的物种的产卵群体生物量造成显著影响。综合与应用。灰海豹与港海豹对鱼类的捕食，不太可能对爱尔兰西南部海域的商业拖网渔业造成损害。该结论与部分针对北大西洋其他海域的模型研究结果存在差异，表明在探讨此类资源冲突时，需依托特定生态系统的实证证据。在海豹与渔业生态位重叠度较低的生态系统中，二者的影响基本相互独立，捕捞压力仍是决定目标鱼类种群状态的主导因素。