The effects of turbidity and complex habitats on the feeding of a galaxiid fish are clear and simple
R. D. Stuart-Smith A B , J. F. Stuart-Smith A , R. W. G. White A and L. A. Barmuta AA School of Zoology and Tasmanian Aquaculture and Fisheries Institute, University of Tasmania, Private Bag 5, Hobart, Tas. 7001, Australia.
B Corresponding author. Email: rstuarts@utas.edu.au
Marine and Freshwater Research 58(5) 429-435 https://doi.org/10.1071/MF06240
Submitted: 12 December 2006 Accepted: 28 February 2007 Published: 17 May 2007
Abstract
The habitat used by animals plays an important role in their interactions with predators and prey. By using complex habitats such as areas of dense macrophyte cover in response to elevated predation risk, small fishes may reduce their foraging success. Because the threat of predation by introduced brown trout increases the use of complex habitats by the threatened Galaxias auratus (Johnston), we experimentally examined its foraging in different habitats to estimate indirect impacts of brown trout presence. The lakes in which G. auratus lives have recently become more turbid, so the experiment was also conducted under different turbidity levels. Laboratory feeding trials in which planktonic and epibenthic prey were simultaneously offered to G. auratus in the presence or absence of artificial macrophytes and at three turbidity levels (0, 50 and 100 NTU) revealed that its overall foraging success was unaffected by habitat complexity; however, in trials with artificial macrophytes, G. auratus consumed a greater proportion of planktonic prey than in the absence of artificial macrophytes. Neither overall foraging success nor prey selection by G. auratus was affected by high turbidity, indicating that water clarity does not appear to directly negatively impact its feeding. The switch in prey types would probably not be detrimental to G. auratus in the long term, and thus it appears that there is no substantial feeding cost associated with its increased use of complex habitats. It could, however, affect lower trophic levels in the lakes to which it is endemic.
Additional keywords: artificial macrophytes, complex habitats, G. auratus, prey switching.
Acknowledgements
The authors wish to thank the Inland Fisheries Service of Tasmania for use of equipment and accommodation for the field component of this study, and two anonymous referees for comments on the original manuscript. R. D. S.-S. was supported by a Tasmanian Aquaculture and Fisheries Institute Postgraduate Scholarship, and further support was provided by the School of Zoology, University of Tasmania. The research was carried under appropriate permits from the Inland Fisheries Service of Tasmania and with the approval of the University of Tasmania Animal Ethics Committee.
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