A comprehensive study of the life history traits of Trematomus newnesi (Pisces, Notothenioidei) off the South Shetland Islands

Abstract

Understanding the life history traits of Antarctic fish species is crucial for effective management and conservation purposes. This study provides a comprehensive evaluation of the reproductive dynamics, age and growth characteristics in Trematomus newnesi, a common nototheniid species in the High-Antarctic zone. Field observations conducted in Potter Cove, South Shetland Islands, revealed significant variations in photoperiod and water temperature from November to March, with water temperatures reaching a peak in mid-December. The gonadosomatic index, as a proxy of gonad development, increased exponentially in both sexes from November to March. Sex steroid plasma levels, particularly testosterone (T) and estradiol (E₂), showed significant temporal variations, with a significant increase in the period when late vitellogenesis was evident, suggesting the proximity of final maturation and spawning. Age estimation through otolith readings provided a range of ages up to five years for both sexes. Comparison with previous studies on T. newnesi from other Antarctic areas highlighted similarities in reproductive patterns and differences in growth parameters. Photoperiod and an increase in temperature resulted to be trigger factors promoting vitellogenesis in T. newnesi, ending in an early austral autumn spawning event. The environmental cues and reproductive data recorded at Potter Cove suggest that this area serves as a spawning ground for T. newnesi. Likewise, larval hatching was estimated to occur from early to mid-August, after an egg incubation period of four months. Overall, this study provides insights into the life history traits of T. newnesi, as a valuable contribution for appropriate management and conservation of Antarctic fish populations.