Size, sex and geographic variation in the diet of the tiger shark, Galeocerdo cuvier, from Western Australian waters

Stomach contents from tiger sharks, Galeocerdo cuvier, caught on lines off the central coast of Western Australia were analysed to investigate variations in the diet due to sex, size and geographic location. Stomachs from 84 specimens contained food, while 26 had empty stomachs and 66 had regurgitated. Twelve prey groups were identified, the most common being turtles, sea snakes, teleost fishes, dugongs and sea birds. Dietary overlap was high between males and females. An ontogenetic shift was observed in the diet. Smaller prey (e.g. cephalopods, teleosts and sea snakes) were more common in small individuals, while the occurrence of larger prey (e.g. turtles, dugongs and elasmobranchs) increased with increasing shark size. Differences in the diet were observed between four regions along the central Western Australian coast. The ability to catch and consume large prey, prey availability, prey density, and prey profitability were identified as factors influencing the diet. The high level of occurrence of dugongs and turtles in the diet of G. cuvier, relative to their abundance, suggests that shark predation may play an important role in regulating populations of these species. [References: 24]

针对在西澳大利亚中部沿岸海域延绳钓捕获的虎鲨（Galeocerdo cuvier）的胃容物开展分析，以探究其食性因性别、体型及地理区位产生的变异。本次研究中，84个样本的胃内含有食物，另有26个样本胃腔为空，66个样本发生胃内容物反流。研究共鉴定出12类猎物类群，其中最常见的猎物类群为海龟、海蛇、硬骨鱼类、儒艮及海鸟。雌雄个体间的食性重叠度较高。研究观察到虎鲨食性存在显著的个体发育性转变：小型个体的胃容物中更常见小型猎物（如头足类、硬骨鱼与海蛇），而大型猎物（如海龟、儒艮及板鳃类）的出现频率随鲨鱼体型增大而显著提升。西澳大利亚中部沿岸的四个区域间，虎鲨食性存在明显差异。研究认定，捕猎与吞食大型猎物的能力、猎物可获得性、猎物密度及猎物收益性为影响其食性的关键因素。相较于野外种群丰度，儒艮与海龟在虎鲨（Galeocerdo cuvier）食性中的出现比例较高，这表明鲨鱼捕食可能对这两类物种的种群调控发挥重要作用。[参考文献：24篇]