Size, Sex And Geographic Variation in the Diet of the Tiger Shark, Galeocerdo Cuvier, From Western Australian Waters |
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Authors: | Colin A Simpfendorfer Adrian B Goodreid Rory B McAuley |
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Institution: | (1) Western Australian Marine Research Laboratories, P.O. Box 20, North Beach, Western Australia, 6020, Australia;(2) Present address: Mote Marine Laboratory, Center for Shark Research, 1600 Ken Thompason Parkway, Sarasota, FL, 34236, U.S.A.;(3) 25 Hopkins Way, Spearwood, Western Australia, 6163, Australia |
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Abstract: | 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. |
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Keywords: | turtle dugong fishery interaction prey diversity ontogenetic dietary shift |
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