Spatial and temporal boundaries to gene flow between Chaenocephalus aceratus populations at South Orkney and South Shetlands

Abstract

ABSTRACT: The black-fin icefish Chaenocephalus aceratus is among the most abundant fish specieson the Antarctic continental shelves of the Scotia Arc, and Bouvet Island. We genotyped 11 micro-satellite loci in C. aceratus population samples from South Orkney, southern South Shetlands, andElephant Island (northern South Shetlands) collected in 2002 and 2006. This investigation furtherdevelops a previous study on the species reporting the presence of one panmittic population in south-ern South Shetlands and Elephant Island, with genetic differentiation between year classes. Ourresults reveal a more complex pattern of differentiation than shown previously, as genetic differencesoccur both at the temporal level at Elephant Island and at the geographic scale between southernSouth Shetland–Elephant Islands and South Orkney population samples. In particular, the mag-nitude of genetic differentiation at the temporal scale, the relatively high effective population size( N e ) and high gene flow indicate that genetic differentiation is not only driven by geographic dis-tance. At present, our results should be taken into account when defining conservation measures andmanagement boundaries in regions where fishery is still open or where other Antarctic fish speciesare still exploited.KEY WORDS: