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Otolith chemistry is more accurate than otolith shape in identifying cod species (genus Pseudophycis) in the diet of Australian fur seals (Arctocephalus pusillus doriferus)

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Fine-scale shape variation and the added effect of partial digestion often limits accurate identification of different teleost prey species in marine diet studies using otoliths. We evaluated the use of fine-scale shape and trace element variation in digested otoliths to identify fish prey species from the diet of predators. Fourier analysis of otolith shape revealed significant variation between red cod (Pseudophycis bachus) and bearded rock cod (Pseudophycis barbata) otoliths. Incorporating otoliths that had been consumed by Australian fur seals (Arctocephalus pusillus doriferus) into a Fourier analysis discriminant model identified 73% of otoliths as those of red cod and 27% as those of bearded rock cod. However, in vitro digestion of red cod and bearded rock cod otoliths resulted in incorrect classification of both cod species otoliths to varying degrees when using Fourier analysis shape descriptors. There was significant variation between red cod and bearded rock cod otolith core chemistry. Incorporating otoliths consumed by the seals into an otolith core chemistry discriminant model identified all otoliths as those of red cod. Using otolith core chemistry to identify prey species was found to be successful, and there is great potential for this technique to have wider applications in investigating ecosystem trophic interactions.

Document Type: Research Article


Affiliations: 1: Department of Zoology, University of Melbourne, Parkville, Victoria 3010, Australia. 2: Fish Ageing Services, P.O. Box 396, Portarlington, Victoria 3223, Australia.

Publication date: October 19, 2011

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  • Published continuously since 1901 (under various titles), this monthly journal is the primary publishing vehicle for the multidisciplinary field of aquatic sciences. It publishes perspectives (syntheses, critiques, and re-evaluations), discussions (comments and replies), articles, and rapid communications, relating to current research on cells, organisms, populations, ecosystems, or processes that affect aquatic systems. The journal seeks to amplify, modify, question, or redirect accumulated knowledge in the field of fisheries and aquatic science. Occasional supplements are dedicated to single topics or to proceedings of international symposia.
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