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Estimation of biological parameters for the bioeconomic evaluation of restocking the Western School Prawn (Metapenaeus dalli) in an Australian estuary

Broadley, A., Tweedley, J.R.ORCID: 0000-0002-2749-1060 and Loneragan, N.R. (2015) Estimation of biological parameters for the bioeconomic evaluation of restocking the Western School Prawn (Metapenaeus dalli) in an Australian estuary. In: 5th International Symposium on Stock Enhancement and Sea Ranching (ISSESR) 2015, 11 - 14 October 2015, Sydney, NSW.

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Abstract

Bioeconomic evaluations of release programs require robust estimates of growth, mortality and reproduction. Length frequency data and mixture analysis were used to estimate biological parameters for the Western School Prawn (Metapenaeus dalli), which is currently being restocked in the Swan-Canning Estuary. Monthly length frequency data, collected from hand and otter trawls on the new moon phase, over 13 lunar cycles, indicated that this species exhibited highly seasonal patterns of growth and reproduction. Growth occurred predominantly in the warmer months (October-April), with little to no growth in the colder months (May-October). The Somers’ seasonal von Bertalanffy growth model estimated that female prawns grew significantly larger (L∞ = 33.72 mm CL, k = 1.06) than their males counterparts (L∞ = 24.20 mm CL, k = 0.97). Gravid females were found only from November to April, when surface and bottom water temperatures ranged from 20 to 27 ºC. Both seasonal and non-seasonal length converted catch curves were used to estimate the instantaneous rate of total mortality Z. The seasonal model demonstrated that female and male mortality were similar (Z = 0.048 and 0.047 week-1, respectively). However, the non-seasonal model showed a greater difference in mortality between females (0.067 week-1) and males and (0.052 week-1). Since fishing mortality is very low, these estimates provide a close approximation for natural mortality M in the population. These results improve our understanding of the biology of M. dalli and will be used in the bioeconomic evaluation of the restocking program.

Item Type: Conference Item
Murdoch Affiliation: Centre for Fish and Fisheries Research
School of Veterinary and Life Sciences
Conference Website: http://searanching.org/searanching5.html
URI: http://researchrepository.murdoch.edu.au/id/eprint/55459
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