Stock enhancement of western school prawn: evaluation of recruitment limitation, environment and release strategies

Comb-crested jacana. Photo by Judy Dunlop/DBCA

Program: Rivers and Estuaries Science

Status: Completed

The iconic western school prawn (Metapenaeus dalli) was once the focus of a small commercial and recreational fishery in the Swan-Canning Estuary, however catches declined significantly through the 1950s and the commercial fishery closed in the mid-1970s.

The popularity of the recreational fishery, which is estimated to have involved more than 50,000 people in the 1980s, also declined. Despite a reduction in fishing effort, stocks failed to recover.

Restocking (releasing cultured individuals to rebuild stocks) was seen as a possible means of increasing the population of M. dalli. Between 2013 and 2016, 4.65 million prawns were grown in aquaculture and released into the Swan-Canning Estuary.

Research was undertaken to complement the restocking effort with the aims of:

determining the biology and ecology of M. dalli, and factors affecting their recruitment
developing release strategies to maximize the survival of hatchery-reared prawns

The research and restocking effort was assisted by community as part of a citizen science project, known as Prawn Watch.

This project has improved understandings of biology, life cycle, predation, and movement patterns of this species, contributing to fishery management. Environmental drivers for distribution and breeding were also identified.

The project showed the prawn population could increase with restocking and that adverse environmental events in rapid succession could have significant impacts on population.

This species occurs in Australian marine waters from Darwin to Cape Naturaliste, but below 31oS it is only found in estuaries. The Swan-Canning population doesn’t recruit from outside and is therefore vulnerable. Given the current low densities, fishing pressure could be minimised through closure zones, periods and bag or gear restrictions.

The project is completed. Spin-off projects are applying model frameworks to better understand the influence of hydrodynamic conditions on prawn habitat.


Dr Kerry Trayler	Dr Steeg Hoeksema
Principal Scientist, Rivers and Estuaries Science	Senior Environmental Officer, Rivers and Estuaries Science

Dr James Tweedley, Murdoch University

Professor Neil Loneragan, Murdoch University

Dr Greg Jenkins, Australian Centre for Applied Aquaculture Research

Fisheries Research and Development Corporation

Department of Primary Industries and Regional Development

RecfishWest

Bennett. A (2014). The influence of sediment compositions on the Western School Prawn, Metapenaeus dalli, in a temperate Australian estuary. Honours Thesis. Murdoch University.

Broadley, A. (2014) Assessing the potential for restocking the western school prawn Metapenaeus dalli in a temperate Australian estuary. Honours thesis, Murdoch University.

Broadley, A.D., Tweedley, J.R. & Loneragan, N.R. (2017). Estimating biological parameters for potential penaeid restocking in a temperate estuary. Fisheries Research. 186(2): 488-501. DOI: 10.1016/j.fishres.2016.09.007

Crisp, Jason (2017) Aspects of reproductive and larval biology relevant to aquaculture-based enhancement of the Western School Prawn (Metapenaeus dalli). PhD thesis, Murdoch University.

Crisp, J.A., Loneragan, N.R, Tweedley, J.R., D’Souza, F.M.L., Poh, B. (2018) Environmental factors influencing the reproduction of an estuarine penaeid population and implications for management. Fisheries Management and Ecology. DOI 10.1111/fme.12278

Crisp, J.A., Partridge, G.L, Tweedley, J.R., D’Souza, F.M.L., Poh, B. (2018) Environmental factors influencing the reproduction of an estuarine penaeid population and implications for management. Fisheries Management and Ecology. DOI 10.1111/fme.12278

Crisp, J.A., Partridge, G.L, D’Souza, F.M.L., Tweedley, J.R., Moheimani, N.R. (2017) Effects of temperature and salinity on larval survival and development of the western school prawn, Metapenaeus dalli. International Aquatic Research DOI: 10.1007/s40071-016-0151-0

Poh, B, Tweedley, J.R. Chaplin, J.A. Trayler, K.M. & Loneragan, N.R. (2018). Estimating predation rates of restocked individuals: The influence of timing-of-release on metapenaeid survival. Fisheries Research. 198: 165-179. DOI: 10.1016/j.fishres.2017.09.019

Poh, B., Tweedley, J.R., Chaplin, J.A Trayler, K.M Crisp, J.A. (2019). Influence of physico-chemical and biotic factors on the distribution of a penaeid in a temperate estuary. Estuarine and Coastal Shelf Science 218: 70-85. DOI: 10.1016/j.ecss.2018.12.003

Trayler, K (2018) Restocking Western School Prawn. Landscope Vol. 34, no 1.

Tweedley, J.R., Loneragan, N.R., Crisp, J.A., Poh, B. Broadley, A.D., Bennett, A.L., Hodson, K.P., Trayler, K.M., Jenkins, G.I., Chaplin, J.A. (2017). Restocking of the Western School Prawn (Metapenaeus dalli) in the Swan-Canning Riverpark. Report for the Fisheries Research and Development Corporation. Murdoch University, Perth, Western Australia. 538 pp.

Tweedley, J.R., Poh, B., Crisp, J.A., Loneragan, N.R (2019). Changes in the abundance of the Western School Prawn (2013-2018) in association with a restocking program. Report for the Department of Biodiversity Conservation and Attractions. Murdoch University, Perth, Western Australia. 60 pp.