Age, growth and maturity of Southern Ocean skates (Bathyraja spp.) from Thekerguelen Plateau

Wong, Jia Wen Darren 2021, Age, growth and maturity of Southern Ocean skates (Bathyraja spp.) from Thekerguelen Plateau, B. Environmental Science (Hons) thesis, School of Life and Environmental Sciences, Deakin University.

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Title Age, growth and maturity of Southern Ocean skates (Bathyraja spp.) from Thekerguelen Plateau
Author Wong, Jia Wen Darren
Institution Deakin University
School School of Life and Environmental Sciences
Faculty Faculty of Science, Engineering and Built Environment
Degree type Honours
Degree name B. Environmental Science (Hons)
Thesis advisor Rizzari, JustinORCID iD for Rizzari, Justin
Date submitted 2021-03-25
Keyword(s) age and growth
Bayesian modelling
Kerguelen Plateau
life history
Summary Commercial fishing practices have raised concerns about the conservation status of manyelasmobranchs. Three species of Southern Ocean skates, Bathyraja eatonii, B. irrasa and B.murrayii, are commonly caught by the fisheries operations around the Heard Island andMcDonald Islands of the Kerguelen Plateau.Vertebrae samples were collected and aged from 249 B. irrasa, 22 B. eatonii and 21 B. murrayi,and the length-at-age data were used to present the first species-specific life history informationfor the three species. Length- and age-at-maturity analyses were conducted, which found thatB.irrasa mature at later ages and larger sizes. B. murrayi had early maturation, and B. eatoniimatured at moderate sizes, but sample sizes for both species were small and therefore theresults should be approached with caution. Growth models were fitted using a multi-modelBayesian approach, which found the Gompertz growth model to be the best fitting models forB. irrasa and B. eatonii based on LOOic values. Growth could not be estimated for B. murrayias age adjustments made to account for assumed asynchronous reproduction resulted in limitedage ranges (i.e. only two age classes) which was insufficient to fit either a Frequentist orBayesian growth model to.The findings from this study support the assumption that B. irrasa is a slow growing, latematuring species which thereby increases the species’ vulnerability to overexploitation. Resultsfrom B. eatonii and B. murrayi were not as conclusive due to the limited samples, but stillprovide valuable information on these data-poor species. The results presented here providescrucial information to help better understand these Bathyraja spp. and subsequently may serveas a foundation to better refine ongoing management strategies and conservation efforts.
Language eng
Indigenous content off
Field of Research 3005 Fisheries sciences
Description of original 57p.
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