Journal of the Royal Society of New Zealand abstracts
The influence of juvenile brown trout (Salmo trutta) on
habitat use of inanga (Galaxias maculatus) in a stream simulator
Martin L. Bonnett
National Institute of Water and
Atmospheric Research Ltd, P. O. Box 8602, Christchurch, New Zealand.
Email: m.bonnett@niwa.co.nz
Angus R. McIntosh
School
of Biological Sciences, University of Canterbury, Private Bag 4800,
Christchurch, New Zealand.
Abstract Introduced salmonid fishes may have
affected native galaxiid fishes in New Zealand by forcing alterations
in their use of spatial resources. A stream simulator was used to test
the effects of juvenile brown trout (Salmo trutta) (fork length
range 66–115 mm) on habitat use of inanga (Galaxias maculatus)
(fork length range 51–100 mm) during autumn. The stream
simulator consisted of a single run-riffle-pool sequence lined with
gravel and cobble substrates, and c. 8 m3 of untreated
artesian water was recirculated through the stream simulator at a rate
of 3 litres s–1. Stream invertebrates were introduced into
the stream simulator to provide food for the fish. Four experiments
were run, each consisting of three 1-day trials using either 10 inanga,
20 inanga, or 10 inanga and brown trout. Counts of inanga visible in
each of 12 designated habitat zones were made throughout the day, and
proportions of visible inanga were used in repeated measure ANOVAs to
test whether the proportion of fish visible varied according to the
time of day, the density of inanga, or the presence of trout. Our
experiments showed that neither the presence of juvenile brown trout
nor the density of inanga had significant influence on inanga habitat
use in the stream simulator. We conclude that in New Zealand streams
any influence of brown trout on inanga is more likely to result from
predation and/or competition for food by larger brown trout.
Keywords Galaxias maculatus; Salmo
trutta; introduced species; interaction; artificial stream; intra-
and interspecific competition
R04006; Received 18 May 2004; accepted 28 October 2004; Online
publication date 6 December 2004
Journal of the Royal Society of New
Zealand Volume 34, Number 4, December, 2004, pp 357–367
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