The Southern and Eastern Scalefish & Shark Fishery (SESSF), covering almost half the Australian Fishing Zone, has historically produced the greatest volume of domestic, wild-caught seafood for the Australian domestic market. Recent evaluations of the biological parameters used in Australian fish stock assessments indicated that over half of the species with outdated or no biological data were SESSF species, including the mesopelagic Frostfish (Lepidopus caudatus). Due to its global distribution, previous biological studies of Frostfish have been conducted in other regions, such as the Mediterranean Sea, Northern Atlantic Ocean & New Zealand waters. In south-eastern Australia, however, where Frostfish is becoming an increasingly important byproduct species of the Blue Grenadier Fishery in waters off Western Tasmanian, contemporary biological information for Frostfish remains scarce.
To help bridge this knowledge gap, biological data, including otoliths, collected from samples (~750) obtained by fishery observers and researchers aboard commercial fishing vessels. To provide high-quality age estimates of Frostfish, whole otoliths were weighed and imaged whole, sectioned, then imaged again, with counts of growth (opaque) zones in the whole otoliths and their corresponding sections recorded independently by two readers. By conducting multiple analyses to assess the precision and repeatability of growth zone counts in whole and sectioned otoliths, including intra/inter-reader comparisons, examination of fish growth covariates such as otolith weight and sex, and application of multiple growth models, comprehensive growth parameter estimates for Frostfish from the SESSF have been developed, along with the construction of a methodological framework of how Frostfish in southeastern Australia can be most effectively aged. More broadly, this study will contribute to a comprehensive understanding of Frostfish and their growth parameters in Australian waters, supporting more holistic resource management models for the fishery.