Life history and population structure of the Antarctic icefish, Pagetopsis maculata (Notothenioidei, Channichthyidae) from the Weddell Sea

Abstract

The life history traits of many large-sized and commercial Antarctic icefishes are reasonably well known, except for smaller species such as Pagetopsis maculata Barsukov and Permitin, 1958. Therefore, we provide, for the first-time, data on growth and reproductive biology of this species based on a representative sample collected in the Weddell Sea during summer. Individual age and gonad stage of development were assessed by sagittal otolith readings and histological analysis of gonads respectively. The sampled population had an equal sex ratio and was composed of adult specimens spread over a wide size range. Both sexes exhibited isometric body growth and comparable condition factors. The estimated life span and growth parameters were similar between sexes, although females attained a larger asymptotic size than males, consistent with the length-frequency distributions. Typically, the reproductive investment of females, based on the gonadosomatic index, was larger than in males, although they both attained sexual maturity at a similar size. Most individuals were at an advanced stage of gonad maturity, indicating imminent spawning in late summer-early autumn. Compared to other icefish species with different geographical distributions, maximum sizes and lifestyles, P. maculata had the lowest growth performance and reproductive investment, primarily because of its smaller body size.