Antarctic fish growth: profile of Trematomus newnesi

Abstract

Life history stages of the Antarctic Peninsula population of the notothenioid Trernaton~us newnesi were examined to gain insights into life history patterns and to understand population processes of ecologically important polar fishes. Sampling yielded 156 larvae and post-larvae and 236 juveniles and adults. Otoliths from these samples were examined for size, morphology and microstructure. External and internal examination of otoliths from 7. newnesi by scanning electron microscopy (SEM) revealed species-specific external shape, and internal rhythmlc patterns. No annual increments could b e identified in T newnesl otol~ths, but apparent daily increments and hatching marks were present. Tetracycline marlung of live f ~s h indicated that increments were formed daily, despite extreme variation in photoperiod. Hatchlng season was estimated by back calculation of otolith increments to be from September to November, with recruitment to adulthood dt age 1 yr. Growth data conformed well to the Gompertz growth equation for juveniles and to the von B~rtalanffy equation for adults. F ~s h grew slowly with the largest fish attaining 7 yr A multivariate mathematical model, relating age to otolith morphometrics and fish size, demonstrated that agc could be reliably determined from body and otolith measurements. This correlation makes it possible to age much larger samples of fish. The life-history profile of T newnesi may be typical of many polar fishes. Otolith methodology appears relevant for obtaining ages for large samples and for studying life history and population dynamics of polar fishes.