基于稳定同位素混合模型的热带东太平洋4种鲨鱼摄食差异

Feeding differences of feeding ecology of four shark species in the tropical eastern Pacific Ocean using stable isotope Mixing model

为了解热带东太平洋海域大洋性鲨鱼的资源利用模式,以大眼长尾鲨(Alopias superciliosus)、浅海长尾鲨(Alopias pelagicus)、锤头双髻鲨(Sphyrna zygaena)和镰状真鲨(Carcharhinus falciformis)为研究对象,通过DNA条形码技术鉴定其胃含物中的饵料生物种类,并利用MixSIAR稳定同位素混合模型计算了主要饵料类群(头足类、小型硬骨鱼和大型硬骨鱼)对4种鲨鱼的贡献率。结果表明:头足类为4种鲨鱼的优势饵料群,小型硬骨鱼对锤头双髻鲨和镰状真鲨的贡献率均较低,而大型硬骨鱼对大眼长尾鲨和浅海长尾鲨的贡献率均较低;大眼长尾鲨性别间和性成熟前后摄食无显著性差异(P>0.05),锤头双髻鲨性别间存在不同优势的饵料群,其余鲨鱼雌鲨和雄鲨均偏好捕食头足类,但贡献率有显著性差异(P<0.05),镰状真鲨性成熟前大型硬骨鱼贡献率最高,性成熟后头足类贡献率最高。研究表明,热带东太平洋海域分布的4种鲨鱼营养水平相似,但仍存在种间和种内的摄食分化和生态位分离,资源分配模式存在差异。

In order to probe for resource utilization of oceanic sharks,preys in the stomach contents were identified in bigeye thresher shark(Alopias superciliosus),pelagic thresher shark(Alopias pelagicus),smooth hammerhead shark(Sphyrna zygaena)and silky shark(Carcharhinus falciformis)from the tropical eastern Pacific(107°W-115°W,17°S-6°N)by using DNA barcode,and then the contribution rates of their main prey groups were calculated using Bayesian mixing model(MixSIAR)to explore intraspecific and interspecific dietary differences.Results showed that cephalopods were paramount prey for four shark species,with small teleosts being the minimal contribution rate to smooth hammerhead and silky shark fishes,and large teleosts for bigeye thresher and pelagic thresher shark.There were different dominant food items between genders of smooth hammerhead shark,without significant difference between maturations and genders of bigeye thresher shark.For silky and pelagic thresher shark,both male and female preferred to prey cephalopods,with the significantly different contribution rates.The main prey was transferred from cephalopods to small teleosts after maturity for silky shark.The findings indicated that trophic positions of four shark species distributed in the tropical eastern Pacific Ocean were similar.However,intraspecific and interspecific dietary differences and niche segregation were observed among these species,and the resource utilizations of four shark species were different.