New Zealand Journal of Marine and Freshwater Research abstracts
A possible false negative: lack of evidence for trout predation on a remnant population of the endangered Macquarie perch, Macquaria australasica, in Cotter Reservoir, Australia
Brendan Ebner
Ben Broadhurst
Mark Lintermans*
Mark Jekabsons
Parks, Conservation and Lands
GPO Box 158, Canberra
ACT 2601, Australia
email: brendan.ebner@act.gov.au
*Present address: Murray-Darling Basin Commission, GPO Box 409, Canberra, ACT, 2601, Australia.
Abstract To investigate possible predation on a remnant population of the endangered Macquaria australasica in Cotter Reservoir, ACT, Australia, stomach content analysis was conducted on 63 rainbow trout Oncorhynchus mykiss and 24 brown trout Salmo trutta. Both predators were found to be piscivorous, with the frequency of piscivory generally increasing with body size. Goldfish Carassius auratus were the only fish species identified in stomach contents. That gape-limitation prevented trout from feeding on juvenile M. australasica was eliminated as a possibility based on: (1) the body depth of prey and the mouth-size of predators; and (2) evidence that another species of similar dimensions was ingested by trout. Whether or not trout predation on M. australasica is an important process in Cotter Reservoir remains to be clarified. Juvenile M. austalasica do not reside in the parts of the reservoir from which most trout were actually sampled in the current study. Therefore, it is proposed that the lack of evidence for predation on M. australasica is potentially a false-negative result.
Keywords piscivory; Salmo trutta; Oncorhynchus mykiss; introduced species; Percichthyidae; Salmonidae
New Zealand Journal of Marine and Freshwater Research, 2007, Vol. 41: 231–237
0028–8330/07/4102–0231 © The Royal Society of New Zealand 2007
M06036; Online publication date 13 June 2007. Received 4 July 2006; accepted 19 December 2006
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