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RESEARCH ARTICLE
Contents Vol 60(8)

Polygamy and low effective population size in a captive Murray cod (Maccullochella peelii peelii) population: genetic implications for wild restocking programs

Meaghan L. Rourke A B D F , Helen C. McPartlan B E , Brett A. Ingram C and Andrea C. Taylor A
+ Author Affiliations
- Author Affiliations

A Australian Centre for Biodiversity, School of Biological Sciences, Monash University, Clayton, Vic. 3800, Australia.

B Primary Industries Research Victoria, Department of Primary Industries, Attwood, Vic. 3049, Australia.

C Primary Industries Research Victoria, Department of Primary Industries, Alexandra, Vic. 3714, Australia.

D Present address: Narrandera Fisheries Centre, NSW Department of Primary Industries, Narrandera, NSW 2700, Australia.

E Present address: Primary Care Research Unit, Department of General Practice, University of Melbourne, Carlton, Vic. 3053, Australia.

F Corresponding author. Email: meaghan.rourke@dpi.nsw.gov.au

Marine and Freshwater Research 60(8) 873-883 https://doi.org/10.1071/MF08218
Submitted: 25 July 2008  Accepted: 21 February 2009   Published: 27 August 2009

Abstract

Stocking of freshwater fish species with hatchery-bred fish is a common response to depleted wild stocks, but may have numerous genetic implications. Murray cod, Maccullochella peelii peelii (Mitchell), have been produced in captivity for wild stocking programs for more than 30 years. The potential genetic impacts of this stocking program on wild populations was investigated by using eight microsatellite markers to determine the parentage of 1380 offspring from 46 separate spawnings collected over three consecutive breeding seasons, and by estimating the effective population size of the broodfish generation through demographic and genetic methods. Results revealed unexpected incidences of polygamous spawnings (both polygyny and polyandry), multiple spawnings by both sexes within a season and repeated matings between pairs of fish across multiple seasons. Furthermore, approximately half of the broodfish failed to spawn at all over the 3-year study period. This likely contributed to the estimated effective population size of around half of the census size, moderate but significant reductions in allelic richness in all three cohorts investigated and a small but significant reduction in heterozygosity in two cohorts. These results allowed us to make recommendations regarding captive husbandry that will maximise genetic diversity of fish intended for stocking.

Additional keywords: microsatellite, parentage analysis, stocking.


Acknowledgements

We sincerely thank the Animal Genetics and Genomics Platform of Primary Industries Research Victoria, where most laboratory work and data analyses were conducted. We also thank the staff of Snobs Creek Hatchery for assisting with sampling and two anonymous reviewers for their valuable comments. The Victorian Government’s Our Rural Landscape Initiative, Fisheries Victoria and the Holsthworth Wildlife Research Fund provided funding for the project. Meaghan Rourke was supported by an Australian Postgraduate Award through Monash University. The research was conducted under animal ethics approvals from the Department of Primary Industries (AEC Fish Nov 05 0001) and Monash University (BSCI/2005/02).


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