Age, growth and maturity of Southern Ocean skates (Bathyraja spp.) from the Kerguelen Plateau

AbstractThree species of Southern Ocean skates, Bathyrajaeatonii,Bathyrajairrasa and Bathyrajamurrayi, are commonly caught as incidental by-catch in fisheries around Heard Island and McDonald Islands of the Kerguelen Plateau. We used length-at-age data to present the species’ life history information (age, growth and maturity for the first-time). Length- and age-at-maturity analyses revealed that B.irrasa matured at > 6 years old and > 1000 mm total length (TL), which was older and larger than B.murrayi (> 5 years old and > 400 mm TL) but similar to B.eatonii (> 5 years old and > 900 mm). We fitted growth models using a multi-model Bayesian framework. Our findings support the assumption that B.irrasa is slow growing and late maturing compared to B.eatonii and B.murrayi, consequently putting it at greater risk to fishery-induced increases in mortality compared to other species (e.g., B.murrayi). This is the first-time age and growth has been estimated for these species, however sample sizes for B.murrayi and B.eatonii were small and hence growth models should be interpreted with caution. Our results represent vital information for population projection models and can therefore assist in the development and/or revision of current by-catch limits to inform ongoing management strategies and conservation efforts.