Impacts of native fish stocking on fish within the Murray-Darling Basin

Impacts of native fish stocking on fish within the Murray-Darling Basin

Fish stocking has been practiced worldwide for centuries, but it is only recently that the environmental and ecological risks have been recognised.  Stocking in the Murray-Darling Basin (MDB) has been largely undertaken either to enhance recreational angling or to aid conservation of a species.  This project reviewed potential impacts of native fish stocking on fish within the MDB, and also provided a summary of stocking activities within the MDB. Potential impacts on abundance and behaviour, genetics, disease and ecosystem level effects were discussed.

Findings

The review focused on 4 potential impacts of stocking:

  • abundance and behavioural responses,
  • genetics implications;
  • spread of disease and;
  • ecosystem level effects.

Changes to abundance and behaviour of fish from stocking mainly arise through competition between stocked and wild fish. These effects can be either direct (for food and habitat) or indirect (habitat alteration, behavioural changes, expansion of species range and displacement of wild stocks). Generally, there has been a lack of research on abundance and behavioural responses to fish stocking on native Australian species.

Genetic impacts of hatcheries and hatchery fish on wild populations have received a lot of attention, but the literature is mainly theoretical in nature.  Genetic effects can be direct (e.g. hybridisation) and indirect (e.g. reduction in population size and genetic diversity caused by predation, competition and diseases).  Artificial breeding of fish also alters the genetics of captive bred populations.  At the time of this project, very little was known about the genetic structure of native fish populations in the MDB.

Impacts of introducing diseases, parasites and exotic organisms unintentionally when stocking fish have also received little attention.  The accidental introduction of a disease with the stocking of native species will most likely have a negative impact on wild populations. There are thought to have been several examples of the spread of pathogens through stocking in the MDB.

Ecosystem alteration from stocking fishes is extremely difficult to demonstrate, and has mostly been attributed to introduced species rather than native species.

The review concluded that targeted research on fish species found in the MDB is needed to better understand all potential impacts. Sound baseline data and monitoring programs are necessary to track changes over time. Stocking will likely result in changes to the receiving system and therefore it is important to ensure that the benefits outweigh the costs and ensure that the goals of any stocking program are met.

Implications for native fish

Many native fish species in the MDB are stocked and the potential impacts outlined in this review should be considered when designing or reviewing stocking programs. This will ensure that the desired effect of stocking programs (i.e. to boost numbers of focus species) will not have negative effect on resident native fish communities. A risk assessment of potential impacts should be undertaken prior to stocking, and experimental evaluation and monitoring of the stocking program considered. Only with such an approach will the success of stocking programs be evaluated and the risks mitigated.

References

Gillanders, B. M., Elsdon, T. S. & Munro, A. R. 2006. Impacts of native fish stocking on fish within the Murray-Darling Basin. School of Earth and Environmental Sciences, University of Adelaide, Adelaide.

Russell, D.J., Jerry, D.R., Thuesen, P.A., Thomson, F.E., Power, T.N. and Smith-Keune, C.S.K. (2013). Fish stocking programs: assessing the benefits against potential long-term genetic and ecological impacts. FRDC Project Number 2009/040. State of Queensland, Department of Agriculture, Fisheries and Forestry and the Fisheries Research and Development Corporation.

Blankenship, H.L. and Leber, K.M. (1995). A responsible approach to marine stock enhancement. In: Schramm, H.L,Jr. and Piper, R.G. (eds). Uses and effects of cultured fish in aquatic ecosystems, American Fisheries Vol 15,  Maryland.

Phillips, B. (ed.) (2003). Proceedings of managing fish translocations and stocking in the Murray-Darling Basin Workshop. World Wide Fund Australia, Canberra.

Arthington A.H. (1991) Ecological and genetic impacts of introduced and translocated freshwater fishes in Australia. Canadian Journal of Fisheries and Aquatic Sciences 48 Suppl. 1:33-43.

Bearlin A.R., Tikel D. (2003) Conservation genetics of Murray-Darling Basin fish; Silver perch (Bidyanus bidyanus), Murray cod (Maccullochella peelii), and Trout cod (M. macquariensis). Phillips B (ed) Managing fish translocation and stocking in the Murray-Darling Basin workshop held in Canberra, 25-26 September 2002: Statement, recommendations and supporting papers. World Wide Fund Australia, p 59-83.

Brumley A.R. (1987) Past and present distributions of Golden perch (Macquaria ambigua)  in Victoria, with reference to releases of hatchery-produced fry. Proceedings of the Royal Society of Victoria 99:111-116.

Cadwallader P.L .(1981) Past and present distributions and translocations of Macquarie perch (Macquaria australasica). Proceedings of the Royal Society of Victoria 93:23-30.

Cadwallader P.L. (1996) Overview of the impacts of introduced salmonids on Australian native fauna. Australian Nature Conservation Agency, Canberra.

Cadwallader P.L, Gooley G.J (1984) Past and present distributions and translocations of Murray cod (Maccullochella peeli) and Trout cod (M. macquariensis ) in Victoria. Proceedings of the Royal Society of Victoria 96:33-43.

Thurstan S., Macdonald J. (2005) Review of existing and proposed methodologies for discriminating hatchery and wild-bred fish, Murray-Darling Basin Commission Project R5003.

Cross T.F. (2000) Genetic implications of translocation and stocking of fish species, with particular reference to Western Australia. Aquaculture Research 31:83-94.

Harris J. (2003) Fish stocking and translocation in the Murray-Darling Basin: issues, benefits and problems. Phillips B (ed) Managing fish translocation and stocking in the Murray-Darling Basin workshop. World Wide Fund Canberra.

Langdon J.S. (1989a) Disease risk of fish introductions and translocations. Pollard DA (ed) Introduced and translocated fishes and their ecological effects.  Proceedings of the 8th Australian Society for Fish Biology Workshop, Magnetic Island, 24-25 August 1989.

Moore A.S, Beaverstock P.R (2003) Trends in fish hatchery practices within New South Wales: what do they tell us about the maintenance of genetic diversity in fish stocking programs? Phillips B (ed) Managing fish translocation and stocking in the Murray-Darling Basin workshop held in Canberra, 25-26 September 2002: Statement, recommendations and supporting papers. World Wide Funf Australia, Sydney, p.104.

Rowland S.J, Tully P. (2004) Hatchery quality assurance program for Murray cod (Maccullochella peelii peelii), golden perch (Macquaria ambigua) and silver perch (Bidyanus bidyanus), New South Wales Department of Primary Industry.

Sanger A.C., Talbot, B. (2003) Management of fish stocking in New South Wales. Phillips B (ed) Managing fish translocation and stocking in the Murray-Darling Basin workshop held in Canberra, 25-26 September 2002: Statement, recommendations and supporting papers. World Wide Fund Australia, Sydney, p 88-93.

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