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Age and growth of the endangered Maugean skate (Zearaja maugeana) using microchemical analysis

Claire van Werven , David Moreno, Sean Tracey, Jeremy Lyle

Abstract

The Maugean skate, Zearaja maugeana, is an endangered species micro-endemic to two small embayments in western Tasmania, Australia. Given the species’ range restriction, status, and exposure to large environmental variability, emerging impacts from anthropogenic pressures are likely to cause additional stress to the population. Information on Maugean skate age and growth is limited. This study estimated the ages of opportunistically sampled Maugean skate (n=44) from Macquarie Harbour between 2012-2019, using incremental banding in their vertebrae. Annual periodicity of growth bands was indirectly verified using LA-ICP-MS measuring the uptake of heavy metals in the vertebrae. Age estimates ranged from 2-10 years. A multi-model inference framework using Akaike’s information criterion corrected for small sample size was used to determine the best fit growth function base on length at age data. A two-parameter VBGF provided the best fit when applied with a fixed length at birth based on two neonate individuals. Females grew faster and reached a larger size than males. The use of archived samples of vertebrae validated with microchemistry demonstrates a novel technique to describe the age and growth and provides critical life history parameters to contribute to population assessments of the endangered Maugean skate population assessments of the endangered population.

MF24240  Accepted 16 January 2025

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