Standard Talk (15 mins) Australian Society for Fish Biology Conference 2022

Life history of the vulnerable Melbourne skate to inform fisheries management and conservation (#132)

Bailee Woolley 1 , David Moreno 1 , Cynthia Awruch 1 , Jaime McAllister 1 , Justin Rizzari 2 , Jayson Semmens 1
  1. Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia
  2. Deakin University , Queenscliff, Victoria, Australia

Due to their large size, slow growth and late maturity, skates are some of the most vulnerable exploited marine fish species. The Melbourne skate (Spiniraja whitleyi), a large skate endemic to the continental shelf of Australia, has experienced localised depletion, a trend attributed to sustained trawling activity over recent years. This, combined with a complete lack of basic knowledge of the species’ biology and ecology, has led to its listing as vulnerable on the International Union for Conservation of Nature (IUCN) red list. Furthermore, the Action Plan for Australian Sharks and Rays (2021) has recommended the assessment of Melbourne skate age, growth and reproduction as high priority. This study therefore aims to address current knowledge gaps by providing data on key life history parameters to inform effective fisheries and conservation management. Reproductive information including sexual maturity and reproductive cycle status was obtained by examining seasonal plasma concentrations of sex hormones (testosterone, oestrogen, and progesterone) using radioimmunoassay. Growth and age parameters were estimated using sagittal cross sections of vertebrae from 40 Melbourne skate individuals ranging in size from 22 cm to 135 cm total length. Yearly growth rings were subsequently counted with transmitted light under a dissecting microscope. Multiple sex specific growth models were applied to determine the curve of best fit for length at age data, with the best model determined using Akaike information criteria.  Age, growth and reproductive estimates will be translated into management actions to ensure the sustainability of this vulnerable species.