Segura-Cobeña Eduardo, Alfaro-Shigueto Joanna, Mangel Jeffrey, Urzua Angel, Górski Konrad
Programa de Magister en Ecología Marina, Facultad de Ciencias, Universidad Católica de la Santísima Concepción, Concepción, Chile.
ProDelphinus, Lima, Perú.
PeerJ. 2021 Apr 22;9:e11283. doi: 10.7717/peerj.11283. eCollection 2021.
Fishery pressure on nursery areas of smooth hammerhead in northern Peruvian coast have become a serious threat to sustainability of this resource. Even though, some management actions focused on conservation of the smooth hammerhead populations were proposed in recent years, their scientific foundations are often limited, and biomass of smooth hammerhead in Peruvian waters continues to decrease. To inform management and conservation, this study aims to evaluate the trophic niche of smooth hammerhead juveniles from three nursery areas in the northern Peruvian coast using stable isotope and fatty acid analyses. First, we compared the environmental characteristics of each nursery area (i.e., sea surface temperature and chlorophyll- concentration) and concluded that nursery areas differed significantly and consistently in sea surface temperature. Subsequently, we evaluated isotopic composition of carbon and nitrogen and fatty acid profiles of muscle and liver tissues collected from juvenile smooth hammerhead from each nursery area. We found that juvenile smooth hammerhead captured in San José were enriched in heavier C and N isotopes compared to those captured in Máncora and Salaverry. Furthermore, the broadest isotopic niches were observed in juveniles from Máncora, whereas isotopic niches of juveniles from Salaverry and San José were narrower. This difference is primarily driven by the Humboldt Current System and associated upwelling of cold and nutrient rich water that drives increased primary production in San José and, to a less extent, in Salaverry. Compared to smooth hammerhead juveniles from Máncora, those from San José and Salaverry were characterised by higher essential fatty acid concentrations related to pelagic and migratory prey. We conclude that smooth hammerhead juveniles from three nursery areas in the northern Peruvian coast differ significantly in their trophic niches. Thus, management and conservation efforts should consider each nursery area as a unique juvenile stock associated with a unique ecosystem and recognize the dependence of smooth hammerhead recruitment in San José and Salaverry on the productivity driven by the Humboldt Current System.
秘鲁北部海岸平滑锤头鲨育幼区面临的渔业压力已对该资源的可持续性构成严重威胁。尽管近年来提出了一些旨在保护平滑锤头鲨种群的管理措施，但其科学依据往往有限，秘鲁海域平滑锤头鲨的生物量仍在持续下降。为了为管理和保护工作提供参考，本研究旨在通过稳定同位素和脂肪酸分析，评估秘鲁北部海岸三个育幼区平滑锤头鲨幼鱼的营养生态位。首先，我们比较了每个育幼区的环境特征（即海面温度和叶绿素浓度），得出各育幼区在海面温度上存在显著且持续的差异。随后，我们评估了从每个育幼区采集的平滑锤头鲨幼鱼肌肉和肝脏组织的碳、氮同位素组成以及脂肪酸谱。我们发现，与在曼科拉和萨拉韦里捕获的幼鱼相比，在圣何塞捕获的平滑锤头鲨幼鱼的碳、氮同位素较重。此外，在曼科拉捕获的幼鱼的同位素生态位最宽，而在萨拉韦里和圣何塞捕获的幼鱼的同位素生态位较窄。这种差异主要是由洪堡洋流系统以及相关的富含冷水和营养物质的上升流驱动的，这导致圣何塞的初级生产力增加，萨拉韦里的增加幅度较小。与来自曼科拉的平滑锤头鲨幼鱼相比，来自圣何塞和萨拉韦里的幼鱼的特征是与远洋和洄游猎物相关的必需脂肪酸浓度较高。我们得出结论，秘鲁北部海岸三个育幼区的平滑锤头鲨幼鱼在营养生态位上存在显著差异。因此，管理和保护工作应将每个育幼区视为与独特生态系统相关的独特幼鱼种群，并认识到圣何塞和萨拉韦里平滑锤头鲨幼鱼的补充依赖于洪堡洋流系统驱动的生产力。
