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BRIEF RESEARCH REPORT article

Front. Fish Sci.
Sec. Fish Biodiversity and Conservation
Volume 2 - 2024 | doi: 10.3389/frish.2024.1518118

Using otolith weights to estimate age for eastern sea garfish, Hyporhamphus australis

Provisionally accepted
John Stewart John Stewart 1*Matt K. Broadhurst Matt K. Broadhurst 1,2Daniel J. Tolhurst Daniel J. Tolhurst 3
  • 1 New South Wales Department of Primary Industries and Regional Development. Fisheries., New South Wales, Australia
  • 2 School of the Environment, University of Queensland, Brisbane, QLD 4072, Australia, Brisbane, Australia
  • 3 The Roslin Institute and Royal (Dick) School of Veterinary Studies, The University of Edinburgh, Easter Bush Campus, Edinburgh, EH25 9RG, UK, Edinburgh, United Kingdom

The final, formatted version of the article will be published soon.

    The most common method of estimating teleost's ages is via sectioned otoliths. With diminishing funding and policies around cost-recovery from fishing industries, exploring cost-effective methods of estimating ages is warranted. The present study used 18 years of size-at-age data collected from monitoring of the commercial halfbeak (Hyporhamphus australis) fishery off New South Wales, Australia, to predict age classes from otolith weight, while considering other sources of variability such as sex, fish length, and year, month and location of capture. We observed a significant linear relationship between age class and mean otolith weight. A generalised linear mixed model predicted 1-year olds with an 82% success rate; but was less successful for other ages. Year of sampling explained the greatest variability in the model and the distributions of otolith weights for each age class had considerable overlap. We conclude that substantial inter-annual variability in the age-class to otolith weight relationship, in addition to the relatively low precision when ageing H. australis by counting annuli in sectioned otoliths, limits the predictive capacity of this model for future monitoring. Nevertheless, substantial cost savings could be made through recalibrating the model for new samples through direct ageing of a subset of otoliths each year. The population of H australis is continuing to rebuild from a previously overfished state, with an expectation that older fish will become more abundant in the fishery. Age estimation from counting annuli in sectioned otoliths is likely to be the most reliable method of identifying older individuals.

    Keywords: Otolith weight, teleost, Ageing, Hyporhamphus, Generalised linear mixed model

    Received: 28 Oct 2024; Accepted: 18 Nov 2024.

    Copyright: © 2024 Stewart, Broadhurst and Tolhurst. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: John Stewart, New South Wales Department of Primary Industries and Regional Development. Fisheries., New South Wales, Australia

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