ECOLOGICAL STUDIES OF ANTARCTIC FISH WITH EMPHASIS ON EARLY DEVELOPMENT OF INSHORE STAGES AT SOUTH GEORGIA

• Main Author: North, Anthony William
• Format: Thesis
• Language: unknown
• Published: 2010
• Subjects: Antarctic; Antarc*; British Antarctic Survey; Copepods
• Online Access: http://hdl.handle.net/10026.2/317

Antarctic fish larvae were investigated in all seasons at South Georgia. This provided material for the first descriptions of the larvae of 10 species. A key to the early stages of 19 of the 21 species of Notothenioidei at South Georgia, and a further 18 species or genera is given. The early development of 17 species is described. Notothenioidei hatch at an early stage, with a primordial fin-fold and without fin-rays although they can soon feed, which is precocious. Sizes when scales first form are reported for six species. Antarctic fish at hatching and metamorphosis are typically larger than those from warmer regions and they feed on larger prey. Notothenioid larvae were generally most abundant within 20 km of South Georgia. In early spring , the six most numerous species were distributed throughout the water column of a 265 m deep fjord; whereas in summer, the four dominant species were restricted to the upper 140 m. Some species undertook diurnalvertical migrations. During winter, the early larvae of three species began feeding on copepods, including adult Drepanopus forcipatus. This copepod was important in the diet of six species in early spring or summer. The relationships of total length to standard length (SL), and weight to SL are given for 12 species. Early larvae of three species grew slowly (<0.08 mm SL d'^). Older larvae of eight species grew at 0.12-0.37 mm SL d'^. Summer growth rates of the larvae of three species at <4°C (>0.25 mm SL d'^) are similar to those of some northern temperate species at their summer temperatures (>14°C). One annulus consisting of a summer and winter zone was formed in the otoliths of three species during each of the first two years. Age determination from annuli inotoliths was validated. British Antarctic Survey Natural Environment Research Council Cambridge, U.K.