ABSTRACT: Dolphins are among the largest and most diverse predators in marine ecosystems, but our understanding of their foraging ecology, which is crucial for ecosystem management, is poor. Delphinus delphis (common dolphins) are found in tropical and temperate waters globally. Stomach content studies indicate they are opportunistic predators that feed locally on abundant small pelagic schooling fish, but information is lacking on how their diet may vary seasonally and with ontogeny. We investigated effects of body length, sex, season, and year on D. delphis diet in the Hauraki Gulf, New Zealand, using carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotope analysis of 56 skin samples collected during 13 years (2004-2016). Dolphin δ¹⁵N values changed with body length, suggesting ontogenetic dietary variation. Nitrogen isotope values were higher in austral autumn/winter compared to spring/summer, whilst δ¹³C values decreased throughout the study period, suggesting temporal changes in primary productivity likely affecting the dolphins’ diet. Sex had a minor effect on dolphin δ¹³C values, with male and female isotopic niches overlapping by 62.6% and 45.2% (respectively). Our results provide a baseline for detecting future changes in the trophic ecology of D. delphis in a key habitat in New Zealand and highlight their role as a sentinel species in this coastal ecosystem.

中文翻译：

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稳定同位素分析揭示普通海豚德尔菲的觅食生态

摘要：海豚是海洋生态系统中最大和最多样化的捕食者之一，但是我们对它们的觅食生态学（对于生态系统管理至关重要）的理解很差。全球热带和温带水域都发现了德尔菲（普通海豚）。胃内容研究表明，它们是机会性的捕食者，它们以丰富的中上层小鱼类为食，但缺乏关于其饮食如何随季节和个体发生变化的信息。我们调查的车身长度，性别，季节的影响，以及今年D. DELPHIS的豪拉基湾，新西兰的饮食，使用碳（δ ¹³ C）和氮（δ ¹⁵ N）的56个皮肤样本稳定同位素分析过程中收集到13年（2004-2016）。海豚δ¹⁵ N值随体长而变化，表明个体发育的饮食差异。氮同位素值相比，春/夏季南半球秋季/冬季较高，而δ ^13个C值在整个研究期间下降，提示时间变化的初级生产力可能影响海豚的饮食。性对豚δ轻微影响^13个C值，与男性和女性同位素壁龛由62.6％和45.2％（分别地）重叠。我们的结果为检测新西兰主要生境中D. delphis营养生态的未来变化提供了基线，并突出了它们在该沿海生态系统中作为前哨物种的作用。