New Zealand Journal of Marine and Freshwater Research abstracts
Impacts of mosquitofish, Gambusia affinis, on black mudfish, Neochanna
diversus
Nicholas Ling
Kate Willis*
Centre for Biodiversity and Ecology Research
Department of Biological Sciences
The University of Waikato
Private Bag 3105
Hamilton, New Zealand
email: nling@waikato.ac.nz
*Present address: Scottish Association for Marine Science, Dunstaffnage
Marine Laboratory, Oban, Argyll, PA37 1QA, Scotland.
Abstract The potential for western mosquitofish, Gambusia
affinis, to negatively affect populations of black mudfish in New Zealand
wetlands was investigated with annual fishing surveys of the Whangamarino wetland
and by laboratory experiments evaluating competition and predation of mosquitofish
on mudfish adults and larvae. Abundance of mudfish juveniles was reduced in
the presence of mosquitofish at marginal wetland sites close to permanent water,
but mosquitofish were not found at ephemeral adult mudfish habitats. In constructed
wetland microcosms, mosquitofish reduced both growth and condition of post-larval
mudfish but did not attack or kill mudfish. In laboratory aquaria, mosquitofish
rapidly consumed mudfish fry but survival time of the latter was significantly
extended by an increase in density of submerged structures and by the presence
of an alternative food source for mosquitofish. Because mosquitofish cannot
survive in ephemeral wetlands that dry over summer, the impacts of mosquitofish
on mudfish are likely to be minimal except in habitats where mosquitofish can
survive year-round owing to the presence of permanent standing water.
Keywords Neochanna diversus; black mudfish; Gambusia
affinis; mosquitofish; competition; predation; conservation
New Zealand Journal of Marine and Freshwater Research, 2005, Vol. 39:
1215–1223
0028–8330/05/3906–1215 © The Royal Society
of New Zealand 2005
M03096; Online publication date 9 November 2005
Received 16 December 2003; accepted 30 June 2005
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