Table_1_Greenland Shark (Somniosus microcephalus) Stomach Contents and Stable Isotope Values Reveal an Ontogenetic Dietary Shift.pdf

Current knowledge on the feeding ecology of the Greenland shark (Somniosus microcephalus), a potential top predator in arctic marine ecosystems, is based on small sample sizes as well as narrow size ranges of sharks. Therefore, potential size-related feeding patterns remain poorly documented. Using stomach content data (N = 88) and stable isotope values of white muscle tissue (N = 40), this study evaluates the diet of sharks ranging in size from 81 to 474 cm (total length). The importance of prey categories (“Fish,” “Mammal,” “Squid,” “Crustacean,” and “Other”) was evaluated based on the reconstructed prey biomass of the stomach contents. Stable isotope values of δ13C and δ15N ranged between -14.4 to -19.9‰ and 11.8 to 17.2‰, respectively. The importance of each prey category was estimated by the Index of Relative Importance (IRI). Our findings suggest that the smallest Greenland sharks (<200 cm) feed on lower trophic level prey, predominantly squids. Larger sharks (>200 cm) mainly feed on higher trophic level prey such as seals, epibenthic and benthic fishes including gadoids (Gadidae), skates (Rajidae), righteye flounders (Pleuronectidae), lumpfish (Cyclopteridae), wolffish (Anarhichadidae), and redfish (Sebastidae). Redfish were, however, only found to be important in the largest sharks sampled (>400 cm). In addition to demonstrating ontogenetic shifts in their feeding preferences, this study supports that Greenland sharks are capable of active predation on fast swimming seals and large fishes.

目前关于格陵兰睡鲨（Somniosus microcephalus）——北极海洋生态系统中的潜在顶级捕食者——的摄食生态学研究，均基于样本量偏小且体型覆盖范围狭窄的鲨类样本，因此其体型相关的摄食模式仍记载匮乏。本研究利用88份胃含物数据与40份白肌组织的稳定同位素比值数据，对总长度介于81至474 cm的格陵兰睡鲨的食性展开评估。本研究基于胃含物重建的猎物生物量，对鱼类、哺乳类、枪乌贼类、甲壳类及其他类别的猎物重要性进行了评估。样本的δ¹³C与δ¹⁵N稳定同位素比值范围分别为-14.4‰至-19.9‰与11.8‰至17.2‰。各猎物类别的重要性通过相对重要性指数（Index of Relative Importance，IRI）进行估算。研究结果显示，体型最小的格陵兰睡鲨（总长度<200 cm）以低营养级猎物为食，主要捕食枪乌贼类；体型更大的个体（总长度>200 cm）则主要摄食高营养级猎物，包括海豹、底上与底栖鱼类，如鳕科（Gadidae）鳕类、鳐科（Rajidae）鳐类、鲽科（Pleuronectidae）右口鲽类、圆鳍鱼科（Cyclopteridae）圆鳍鱼、狼鳚科（Anarhichadidae）狼鱼以及鲉科（Sebastidae）红鱼类。但红鱼类仅在采样的最大体型个体（总长度>400 cm）中被认定为重要猎物。本研究不仅揭示了格陵兰睡鲨摄食偏好的个体发育转变，同时证实其具备主动捕食游动迅速的海豹与大型鱼类的能力。