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Increasing turbidity significantly alters the diet of brown trout: a multi-year longitudinal study


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Stuart-Smith, RD, Richardson, AMM and White, RWG 2004 , 'Increasing turbidity significantly alters the diet of brown trout: a multi-year longitudinal study' , Journal of Fish Biology, vol. 65 , pp. 376-388 , doi: 10.1111/j.0022-1112.2004.00456.x.

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The stomach contents of adult brown trout Salmo trutta from Lake Sorell, Tasmania, were
analysed during 6 years of increasing turbidity to follow changes in the diet associated with
dramatic changes in water clarity. Brown trout were sampled from 1996, when turbidity was 26
NTU, to 2001 when turbidity was 141NTU. The mean relative volume of stomach contents
decreased progressively to 2001, by which time it was only one sixth of that in 1996, and the mean
diversity of prey in stomachs decreased from an average of more than six species per stomach in
1996 to one species in 2001. The species composition of stomach contents shifted from domination
by the phreatoicid isopod Colubotelson sp., to the galaxiid fish Galaxias auratus and the
amphipod Austrochiltonia australis, and then the cladoceran Daphnia carinata. To give an
indication of diet changes over a typical yearly cycle in the current turbid state of the lake, a
sample was taken from each season from December 2000 to September 2001. Two basic diets
were found during the year; brown trout specialized on D. carinata in summer and autumn, and
G. auratus in winter and spring. Mean diversity of prey was less than two species per stomach in
all samples from 2000 to 2001, except for the sample from spring 2001 when it was 22 species per
stomach, and the mean relative volume of stomach contents was more than three times greater in
winter than any other season. The ways in which high turbidity may have influenced the changes
in the brown trout diet observed since 1996 and the patterns evident during the seasons of
2000-2001 are discussed.

Item Type: Article
Authors/Creators:Stuart-Smith, RD and Richardson, AMM and White, RWG
Keywords: Daphnia carinata, feeding, Galaxias auratus, Tasmanian lake, trophic adaptability.
Journal or Publication Title: Journal of Fish Biology
ISSN: 0022-1112
DOI / ID Number: 10.1111/j.0022-1112.2004.00456.x
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