Otolith shape as a tool for species identification and management of grenadiers in the Sub-Antarctic

Supervisory Team:

Alyssa Marshell

Cara Miller

Brief project description:

Numerous grenadier species are bycaught in Sub-Antarctic fisheries. However, similarities in external morphology of some grenadier species sometimes hinders the ability of fisheries observers to accurately distinguish grenadiers to the individual species level. Recent research on using otolith shape to differentiate Macrourus caml and M. whitsoni have reported relatively high levels of prediction accuracy (Moore et al. 2022). Hence, it is plausible that post-hoc confirmation of species along with biological field measurements may provide a useful tool to improve and enhance the taxonomic classification of grenadiers.

This project intends to process historical otolith collections and examine associated biological information for four grenadier species (M. caml, M. whitsoni, M.holotrachys, and M. carinatus) collected in commercial fisheries operating within the Sub-Antarctic waters of Heard Island and McDonald Islands (HIMI) to: (i) evaluate whether otolith shape can reliably be used to differentiate between grenadier species caught within HIMI waters, (ii) explore whether there are species-specific patterns of habitat use, age-class structure, and catch composition by grenadier species’ or species-complex, and (iii) based on these findings provide policy advice for management of grenadiers in HIMI fisheries.

Skills students will develop during this research project:

  • Laboratory skills in the cutting, preparation and ageing of fish otoliths
  • High resolution microscopic image capture
  • Measurement and characterisation of otolith shape and morphometrics
  • Applied statistical analysis of both digital otolith images and biological measurements
  • Application of findings within a relevant fisheries management framework
Authorised by the Executive Director, Institute for Marine and Antarctic Studies
November 28, 2022