Biogeography and life history ameliorate the potentially negative genetic effects of stocking on Murray cod (Maccullochella peelii peelii)
Meaghan L. Rourke A B D F , Helen C. McPartlan B E , Brett A. Ingram C and Andrea C. Taylor AA 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 Marine and Freshwater Fisheries Research Institute, Fisheries Victoria, Department of Primary Industries, Alexandra, Vic. 3714, Australia.
D Present address: Narrandera Fisheries Centre, Industry and Investment NSW, 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@industry.nsw.gov.au
Marine and Freshwater Research 61(8) 918-927 https://doi.org/10.1071/MF10037
Submitted: 15 February 2010 Accepted: 20 May 2010 Published: 13 August 2010
Abstract
Stocking wild fish populations with hatchery-bred fish has numerous genetic implications for fish species worldwide. In the present study, 16 microsatellite loci were used to determine the genetic effects of nearly three decades of Murray cod (Maccullochella peelii peelii) stocking in five river catchments in southern Australia. Genetic parameters taken from scale samples collected from 1949 to 1954 before the commencement of stocking were compared with samples collected 16 to 28 years after stocking commenced, and with samples from a local hatchery that supplements these catchments. Given that the five catchments are highly connected and adult Murray cod undertake moderate migrations, we predicted that there would be minimal population structuring of historical samples, whereas contemporary samples may have diverged slightly and lost genetic diversity as a result of stocking. A Bayesian Structure analysis indicated genetic homogeneity among the catchments both pre- and post-stocking, indicating that stocking has not measurably impacted genetic structure, although allele frequencies in one catchment changed slightly over this period. Current genetic diversity was moderately high (HE = 0.693) and had not changed over the period of stocking. Broodfish had a similar level of genetic diversity to the wild populations, and effective population size had not changed substantially between the two time periods. Our results may bode well for stocking programs of species that are undertaken without knowledge of natural genetic structure, when river connectivity is high, fish are moderately migratory and broodfish are sourced locally.
Additional keywords: effective population size, genetic diversity, historical scale samples, microsatellite, Murray–Darling Basin.
Acknowledgements
This work was supported by an Australian Postgraduate Award through Monash University, the Victorian Government’s Our Rural Landscapes Initiative, the Recreational Fishing Trust and the Holsthworth Wildlife Research Fund. We thank Queensland DPI, NSW Industry and Investment and Fisheries Victoria for providing Murray cod stocking records. We also thank J. Douglas, R. Strongman, J. Lieschke, A. King, D. Crook, A. Bearlin, K. Pomorin, D. Gilligan, B. Zampatti, D. Bray, D. Tikel, N. Murray, B. Malcolm, J. Pritchard and countless recreational anglers for assisting with sample collection. We are grateful to S. Rowland and J. Douglas for sharing their extensive knowledge of Murray cod, and to two anonymous reviewers for suggesting improvements to the manuscript. 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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