The first population of mosquitofish, Gambusia holbrooki, was discovered in a wetland area of the upper Tamar Estuary, northern Tasmania, Australia, in November 2000. We report aspects of the structure and reproductive biology of this population, based on 1567 fish collected between August 2001 and January 2002. Females dominated most catches. Maximum lengths were 48.9 and 23.6 mm standard length (SL) for females and males, respectively. Growth of the over-wintered cohort was evident from October, when temperatures reached >19°C; growth rates in the young-of-season cohort from length frequency plots were 0.38 mm/ day for females and 0.19 mm/day for males. Estimated SL at 50% maturity for females (25.0 mm) and males (17.4 mm) were attained within 7 weeks of birth. Developing embryos were present from mid October and offspring from mid November; average number of stage III embryos was 55.5 (3-144). Given their rapid reproductive turnover (c. 34-day gestation period) and resilience to broad environmental conditions, it is likely that this exotic pest will spread to other Tasmanian localities, as it has already been discovered in areas near the wetlands since the completion of this study.

Item Type:	Refereed Article
Research Division:	Agricultural, Veterinary and Food Sciences
Research Group:	Fisheries sciences
Research Field:	Fisheries sciences not elsewhere classified
Objective Division:	Environmental Management
Objective Group:	Marine systems and management
Objective Field:	Measurement and assessment of marine water quality and condition
UTAS Author:	Keane, JP (Dr John Keane)
UTAS Author:	Neira, FJ (Dr Francisco Neira)
ID Code:	36039
Year Published:	2004
Web of Science® Times Cited:	13
Deposited By:	TAFI - Marine Research Laboratory
Deposited On:	2005-09-30
Last Modified:	2005-09-30
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