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Natural mortality of Trachurus novaezelandiae and its size selection by purse seines off south-eastern Australia

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Broadhurst, M. K., Kienzle, M. and Stewart, J. (2018) Natural mortality of Trachurus novaezelandiae and its size selection by purse seines off south-eastern Australia. Fisheries Management and Ecology, 25 (5).

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Article Link: https://doi.org/10.1111/fme.12286

Publisher URL: https://onlinelibrary.wiley.com/doi/abs/10.1111/fme.12286


Abstract The natural mortality (M) and purse-seine catchability and selectivity were estimated for yellowtail scad, Trachurus novaezelandiae, Richardson, a small inshore pelagic species harvested off south-eastern Australia. Hazard functions were applied to two decades of data describing catches (mostly stable at a mean ± SE of 315 ± 14 t p.a.) and effort (declining from a maximum of 2,289 to 642 boat days between 1999/2000 and 2015/2016) and interdispersed (over 9 years) annual estimates of size at age (0+ to 18 years) to enable survival analysis. The data were best described by a model with eight parameters, including catchability (estimated at <0.1 × 10−7 boat/day), M (0.22/year) and variable age-specific selection up to 6 years with a 50% retention among 5-year-olds (larger than the estimated age at maturation). The low catchability implied very low fishing mortality by the purse-seine fleet. Ongoing monitoring and applied gear-based studies are required to validate purse-seine catchability and selectivity, but the data nevertheless imply T. novaezelandiae could incur additional fishing effort and, in doing so, alleviate pressure on other regional small pelagics.

Item Type:Article
Business groups:Animal Science
Subjects:Aquaculture and Fisheries > Fisheries > Fishery resources
Aquaculture and Fisheries > Fisheries > Fishery conservation
Aquaculture and Fisheries > Fisheries > Fishery management. Fishery policy
Live Archive:04 Mar 2019 06:24
Last Modified:03 Sep 2021 16:44

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