Bachiller Eneko, Giménez Joan, Albo-Puigserver Marta, Pennino Maria Grazia, Marí-Mena Neus, Esteban Antonio, Lloret-Lloret Elena, Bellido José María, Coll Marta
Marine Renewable Resources Department Institute of Marine Science (ICM-CSIC) Barcelona Spain.
MaREI Centre Environmental Research Institute University College Cork Cork Ireland.
Ecol Evol. 2021 Nov 10;11(22):16126-16142. doi: 10.1002/ece3.8293. eCollection 2021 Nov.
The northward expansion of round sardinella () in the Mediterranean Sea, together with declines and fluctuations in biomass and landings of European sardine () and anchovy () observed in recent decades, may suggest potential inter-specific competition in the pelagic domain. The coexistence of sympatric zooplanktivorous fish species might therefore be exposed in part to trophic niche overlap and competition for food. Combining visual diet characterization under the microscope with DNA metabarcoding from stomach contents of fish collected in spring results show that predation on relatively large krill is equally important for sardinella than for the other two niche overlapping species. Furthermore, an important overlap is found in their isotopic niche, especially with anchovy, using nitrogen (δN) and carbon (δC) stable isotopes in muscle tissue. In fact, the three fish species are able to feed effectively in the whole prey size spectrum available during the sampled season, from the smallest diatoms and copepods to the larger prey (i.e., decapods and euphausiids), including fish larvae. Moreover, effective predation upon other large prey like siphonophores, which is observed only when multi-proxy analyses in stomach contents are applied, might also be relevant in the diet of sardinella. The overlapping diet composition in spring, together with the effective use of food resource by sardinella, can be of special interest in potential future scenarios with warmer water temperature leading to lower zooplankton and/or higher jellyfish availability, where sardinella may take advantage over other species due to its feeding plasticity.
地中海圆沙丁鱼（）向北扩张，以及近几十年来观察到欧洲沙丁鱼（）和凤尾鱼（）的生物量和渔获量下降及波动，可能表明在中上层领域存在潜在的种间竞争。因此，同域分布的浮游动物食性鱼类物种的共存可能部分受到营养生态位重叠和食物竞争的影响。将显微镜下的视觉饮食特征与春季采集的鱼类胃内容物的DNA代谢条形码相结合的结果表明，捕食相对较大的磷虾对沙丁鱼和其他两个生态位重叠物种同样重要。此外，利用肌肉组织中的氮（δN）和碳（δC）稳定同位素发现，它们的同位素生态位存在重要重叠，尤其是与凤尾鱼。事实上，这三种鱼类能够在采样季节可获得的整个猎物大小范围内有效觅食，从最小的硅藻和桡足类到较大的猎物（即十足目和磷虾），包括鱼卵。此外，仅在对胃内容物进行多指标分析时才观察到的对其他大型猎物（如水螅水母）的有效捕食，在沙丁鱼的饮食中可能也很重要。春季重叠的饮食组成，以及沙丁鱼对食物资源的有效利用，在未来水温升高导致浮游动物数量减少和/或水母数量增加的潜在情景中可能特别值得关注，在这种情况下，沙丁鱼可能因其摄食可塑性而比其他物种更具优势。
