Life history traits of Notothenia rossii and N-coriiceps along the southern Scotia Arc

Notothenia coriiceps and Notothenia rossii are two widespread nototheniid fishes, that live sympatrically along the southern Scotia Arc from South Georgia to the South Shetland Islands. In this sector of the Southern Ocean, they experienced different exploitation rates in the past and exhibit different habitat and food preferences as adult. Aiming to evaluate the influence of these factors in shaping life history traits of these species, we compare the reproductive investment and the age structure between the species and in N. rossii, between populations inhabiting different areas. Based on histological analyses, the two species share the same pattern of gamete development in both sexes. The potential fecundity was similar and was positively related to fish size in both species, being relatively high with respect to other notothenioids and in terms of egg size at deposition. Based on sagittal otolith readings, the growth rate and maximum age recorded differed significantly between the two species. Notothenia rossii exhibited a higher growth rate and a comparatively lower maximum age than N. coriiceps. Similarly, N. rossii attained sexual maturity at the same age but at a larger size than N. coriiceps. At the intraspecific level, no differences in life history traits were observed between the populations of N. rossii collected from different areas. Consistent with the different levels of fishing pressure exerted on these species and their low resilience, a recent significant decrease over time in the maximum fish size and related reproductive potential has been observed only in the overexploited populations of N. rossii.