Competition for space between introduced brown trout ( Salmo trutta L.) and a native galaxiid ( Galaxias vulgaris Stokell) in a New Zealand stream

Competition for space between introduced brown trout ( Salmo trutta L.) and a native galaxiid (... Increasing circumstantial evidence indicates that the introduction of brown trout (Salmo trutta L.) to New Zealand has caused a widespread decline in native fish populations but few of the underlying mechanisms have been investigated. The possibility of spatial competition was investigated by comparing the microhabitat used by native Galaxias vulgaris Stokell (Family Galaxiidae) that were sympatric and allopatric with brown trout. A range of microhabitat variables was measured from random locations where G. vulgaris were present in the Shag River during the day. G. vulgaris preferred coarse substrates, using them as resting places, but showed no other microhabitat preferences. This pattern of microhabitat use did not change in the presence of brown trout although galaxiid densities were considerably lower. Experiments in in situ stream channels confirmed that competition for space does not occur during the day even at high galaxiid densities. This situation changed dramatically at night, however, with G. vulgaris spending significantly more time in slower areas when trout were present. G. vulgaris feeds on drifting invertebrates, so brown trout could affect the galaxiids deleteriously by forcing them to occupy less profitable feeding positions. Interspecific competition for space, perhaps combined with competition for food and predation by trout, could explain declines in G. vulgaris populations. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Fish Biology Wiley

Competition for space between introduced brown trout ( Salmo trutta L.) and a native galaxiid ( Galaxias vulgaris Stokell) in a New Zealand stream

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Publisher
Wiley
Copyright
Copyright © 1992 Wiley Subscription Services, Inc., A Wiley Company
ISSN
0022-1112
eISSN
1095-8649
D.O.I.
10.1111/j.1095-8649.1992.tb03170.x
Publisher site
See Article on Publisher Site

Abstract

Increasing circumstantial evidence indicates that the introduction of brown trout (Salmo trutta L.) to New Zealand has caused a widespread decline in native fish populations but few of the underlying mechanisms have been investigated. The possibility of spatial competition was investigated by comparing the microhabitat used by native Galaxias vulgaris Stokell (Family Galaxiidae) that were sympatric and allopatric with brown trout. A range of microhabitat variables was measured from random locations where G. vulgaris were present in the Shag River during the day. G. vulgaris preferred coarse substrates, using them as resting places, but showed no other microhabitat preferences. This pattern of microhabitat use did not change in the presence of brown trout although galaxiid densities were considerably lower. Experiments in in situ stream channels confirmed that competition for space does not occur during the day even at high galaxiid densities. This situation changed dramatically at night, however, with G. vulgaris spending significantly more time in slower areas when trout were present. G. vulgaris feeds on drifting invertebrates, so brown trout could affect the galaxiids deleteriously by forcing them to occupy less profitable feeding positions. Interspecific competition for space, perhaps combined with competition for food and predation by trout, could explain declines in G. vulgaris populations.

Journal

Journal of Fish BiologyWiley

Published: Jul 1, 1992

References

  • Breeding biology of a non‐diadromous galaxiid, Galaxias vulgaris Stokell, in a New Zealand river
    Cadwallader, Cadwallader
  • Habitat shifts in rainbow trout: competitive influences of brown trout
    Galtz, Galtz; Sale, Sale; Loar, Loar
  • Influence of physical factors on density of stocked brown trout ( Salmo trutta ) in a Danish lowland stream
    Hermansen, Hermansen; Krog, Krog

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