Antarctic fish growth: profile of Trematomus newnesi

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Abstract
Life history stages of the Antarctic Peninsula population of the notothenioid Trematomus 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 T. newnesi by scanning electron microscopy (SEM) revealed species-specific external shape, and internal rhythmic patterns. No annual increments could be identified in T. newnesi otoliths, but apparently daily increments and hatching marks were present. Tetracycline marking of live fish indicated that increments were formed daily, despite extreme variation in photoperiod. Hatching season was estimated by back calculation of otolith increments to be from September to November, with recruitment to adulthood at age 1 yr. Growth data conformed well to the Gompertz growth equation for juveniles and to the von Bertalanffy equation for adults. Fish grew slowly with the largest fish attaining 7 yr. A multivariate mathematical model, relating age to otolith morphometrics and fish size, demonstrated that age 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.