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Reproduction, growth and diet of Gambusia holbrooki (Girard) in a temperate Australian river

Pen, L.J. and Potter, I.C. (1991) Reproduction, growth and diet of Gambusia holbrooki (Girard) in a temperate Australian river. Aquatic Conservation: Marine and Freshwater Ecosystems, 1 (2). pp. 159-172.

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1. The biology of Gambusia holbrooki in the Collie River in southwestern Australia is described using data obtained from seine samples collected at 4–6 weekly intervals over two years.

2. Females which had overwintered in the river bred between October and February (spring-breeding group) and then died. Some of the large representatives of the resultant cohort of males and females bred between January and March (summer-breeding group) and then also died. The offspring of these larger individuals and the smaller fish did not start breeding until the following spring, when they constituted the spring-breeding group of the following breeding season. Breeding occurred when temperatures were above 15–16°C and day length exceeded 750–780 min. The increase in the mean length of the spring group of pregnant females from 33 mm in October to 52 mm in January was accompanied by a rise in mean fecundity from 33 to 131.

3. In the Collie River, G. holbrooki is a generalist carnivore, feeding at the water surface and throughout the water column. Gut contents of a wide size range of G. holbrooki from each season contained neither the eggs, larvae, juveniles nor adults of any of the three indigenous fish species found in the system. Moreover, there was no evidence that G. holbrooki exhibited agonistic behaviour, such as fin clipping, towards these native fish.

4. Coexistence of the three indigenous species with G. holbrooki, and thereby their conservation, is facilitated by the outcome of different spawning times and localities. Thus, the early life-history stages of the indigenous species, which are most susceptible to predation, are typically produced in tributary creeks or flood waters between late winter and late spring, some time before the breeding of G. holbrooki results in a population explosion of this exotic species in the main channel of the river during summer.

Item Type: Journal Article
Murdoch Affiliation(s): School of Biological and Environmental Sciences
Publisher: John Wiley & Sons Inc.
Copyright: © 1991 John Wiley & Sons, Ltd
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