Ecology of the Tiger Shark (Galeocerdo cuvier) in Shark Bay.

Tiger sharks, Galeocerdo cuvier, are apex predators in a variety of nearshore ecosystems throughout the world. This study investigates the biology of tiger sharks in the shallow seagrass ecosystem of Shark Bay, Western Australia. Tiger sharks (n = 252) were the most commonly caught species (94%) compared to other large sharks. Tiger sharks ranged from 148-407cm TL. The overall sex ratio was biased towards females (1.8:1), but the sex ratio of mature animals (> 300cm TL) did not differ from 1:1. Contrary to previous accounts, tiger sharks were caught more often in all habitats during daylight hours than at night. Tiger shark catch rates were highly correlated with water temperature and were highest when water temperatures were above 19°C. The seasonal abundance of tiger sharks is correlated to both water temperature and the occurrence of their main prey: sea snakes and dugongs, Dugong dugon. Stomach contents analysis indicated that sea turtles and smaller elasmobranchs were also common prey. The importance of major seagrass grazers (dugongs and green sea turtles, Chelonia mydas) in the diet of tiger sharks suggests the possibility that these sharks are keystone predators in this ecosystem.

鼬鲨（Galeocerdo cuvier）是全球各类近岸生态系统中的顶级捕食者。本研究针对澳大利亚西部鲨鱼湾浅海海草生境中的鼬鲨开展生物学调查。本次共捕获鼬鲨252尾，占所有捕获大型鲨鱼物种的94%，为最常捕获的物种。捕获的鼬鲨个体总长度介于148至407厘米之间。整体性别比例偏向雌性（1.8:1），但体长超过300厘米的成熟个体性别比例与1:1无显著差异。与既往研究报道相悖，鼬鲨在所有生境中的日间捕获率均高于夜间。鼬鲨的捕获率与水温呈显著相关，在水温高于19℃时捕获率达到峰值。鼬鲨的季节丰度与水温，以及其主要猎物——海蛇和儒艮（Dugong dugon）的出现频次均存在相关性。胃容物分析结果显示，海龟以及小型软骨鱼类同样为鼬鲨的常见猎物。海草生境的主要植食者（儒艮与绿海龟（Chelonia mydas））在鼬鲨食谱中的重要性，提示鼬鲨可能是该生态系统中的关键捕食者。