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Diet estimation based on an integrated mixed prey feeding experiment using Arctocephalus seals


Casper, RM and Gales, NJ and Hindell, MA and Robinson, SM, Diet estimation based on an integrated mixed prey feeding experiment using Arctocephalus seals, Journal of Experimental Marine Biology and Ecology, 328, (2) pp. 228-239. ISSN 0022-0981 (2006) [Refereed Article]

DOI: doi:10.1016/j.jembe.2005.07.009


Food web models depend on identifying which taxa are eaten and in what proportion they are consumed. Arctocephalus seals are generalist foragers and are an ongoing focus of Southern Hemisphere marine ecosystem research. This is the first feeding experiment to use Arctocephalus spp. to assess the utility of hard part scat analysis for diet estimation, based on mixed prey diets integrated over several days. Recovery rates of otoliths were extremely low for all taxa (0-9%). Although we could not collect scats produced during a 90 min period each day, during which the seals had access to a large pool, this result could not be attributed to otolith robustness, pinniped species or class, activity level, meal size or frequency, or fat content of the diet. We conclude that the unusually low recovery rates in this study may be due to unaccounted scats produced during 90 min of each day, if they contained otolith numbers an order of magnitude greater than all otoliths retrieved from scats produced during the other 22.5 h of each day, and/or may be related to the digestive processing of a mixed prey diet. Our study demonstrates the inadequacy of using otoliths in field collected scats for diet estimation due to the high level of unexplained variability of otolith occurrence in scats. We also identify two new potential sources of this variability. These are variability in numbers of otoliths per scat depending on activity level when a scat is excreted, and variability in recovery rates of otoliths as a function of the complexity of the diet. © 2005 Elsevier B.V. All rights reserved.

Item Details

Item Type:Refereed Article
Research Division:Environmental Sciences
Research Group:Environmental management
Research Field:Wildlife and habitat management
Objective Division:Environmental Management
Objective Group:Coastal and estuarine systems and management
Objective Field:Assessment and management of coastal and estuarine ecosystems
UTAS Author:Casper, RM (Dr Ruth Casper)
UTAS Author:Hindell, MA (Professor Mark Hindell)
ID Code:42669
Year Published:2006
Web of Science® Times Cited:22
Deposited By:Zoology
Deposited On:2006-08-01
Last Modified:2007-04-27

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