Diversity, relative abundance, new locality records and population structure of Antarctic demersal fishes from the northern Scotia Arc islands and Bouvetoya

A primary objective of the ICEFISH 2004 cruise was to collect and study notothenioid fishes from remote localities in the Atlantic sector of the Southern Ocean. Nearly 1 month was devoted to bottom trawling for fishes on the shelf and upper slope (to 1,000 m) areas around Shag Rocks, South Georgia, South Sandwich Islands and Bouvetoya. The focus was on the latter two locations, because their faunas are more poorly known. Eight species were collected at Shag Rocks with Patagonotothen guntheri most abundant; 17 at South Georgia with Lepidonotothen nudifrons, L. larseni and Gobionotothen gibberifrons most abundant; 13 at the South Sandwich Islands with L. larseni, L. nudifrons and G. gibberifrons most abundant; and 11 at Bouvetoya with L. larseni, Macrourus holotrachys and L. squamifrons most abundant. Ten new locality records were established: Shag Rocks (1), South Georgia (1), South Sandwich Islands (5), South Sandwich Trench at 5,350 m (1) and Bouvetoya (2). Total known demersal fish diversity on the shelf and upper slope at Shag Rocks/South Georgia, South Sandwich Islands and Bouvetoya is 42, 31 and 17 species, respectively. To examine population structure in the four most abundant notothenioids at Bouvetoya (L. larseni, L. squamifrons, Notothenia coriiceps and Chaenocephalus aceratus), we examined the ND2 portion of mitochondrial DNA. Chaenocephalus aceratus, N. coriiceps and L. larseni exhibited no significant genetic differentiation in comparison with samples from localities in the Scotia Sea and the Antarctic Peninsula. However, L. squamifrons showed significant genetic differentiation between the South Shetlands and Bouvetoya populations (F-ST = 0.189, P = 0.015). Thus, these data combined with previous studies of two other notothenioids suggest that five of the six notothenioid species at Bouvetoya are not genetically differentiated from other localities in the Atlantic sector of the Southern Ocean. The location of Bouvetoya within the Antarctic Circumpolar Current and the long (1-2 years) pelagic stages of the notothenioids at Bouvetoya may be at least partly responsible for this genetic homogeneity.