Annual changes in species composition and abundance of myctophid fish in the north of South Georgia (CCAMLR Subarea 48.3), Antarctica, during austral winter from 2002 to 2008

Species composition and abundance of myctophid fish were analyzed using the fish bycatch samples collected by scientific observers onboard Japanese commercial krill fishing vessels in the area north and northwest of South Georgia, Antarctica during the austral winter from 2002 to 2008. A total of 9 myctophid species were identified in the by-catch samples, among which Krefftichthys anderssoni, Gymnoscopelus nicholsi and Protomyctophum choriodon were abundant. Different life stages of K. anderssoni and G. nicholsi from larvae to adults were found, suggesting that these species may have their nursery ground around South Georgia. Electrona antarctica was not a major component of the recent mesopelagic ichthyofauna in this area, though this species used to dominate in the Antarctic coastal waters. In contrast, P. choriodon, which is known as a temperate species, became to dominate the recent samples. Additionally, the size distribution of P. choriodon was unimodal, indicating that individuals in the samples belonged to the same size group and probably migrated from the population in northern warmer areas.