By-catch, growth and feeding of Antarctic juvenile fish taken in krill (Euphausia superba Dana) fisheries in the South Georgia area, in 1992
This paper discusses an investigation of juvenile Antarctic fish caught during krill fishing by the FV Grigory Kovtun in the area around South Georgia from May to July 1992. Two species were predominant in the by-catches: Champsocephalus gunnari and Nototheniops larseni. The frequency of occurrence of juvenile fish was 18.2% when all krill tows were included and 45.5% when only tows made in shelf waters were considered. The abundance of juvenile fish in catches, normalised to one tonne of krill, ranged from 700 to 18 900 individuals. In the case of C. gunnari, average values were 966 ± 225 ind./tonne krill and 2 434 ± 579 ind./tonne krill for all trawls and for shelf trawls, respectively. For N. larseni the corresponding averages were 557 ± 103 and 1 388 ± 248. The mean standard length of C. gunnari was 68.5 to 79.7 mm in May and June and 93 mm in late July. The mean growth rate of this species over this period is estimated to be 0.37 mm per day. In May to June, N. larseni juveniles were represented by fingerlings (mean length of 42.4 to 47.4 mm) and yearlings (72.5 to 73.7 mm). In late July the mean length of fingerlings increased to 48.5 mm. The mean daily length increase in N. larseni is estimated to be 0.08 mm. The diet, by mass, of both C. gunnari fingerlings and N. larseni yearlings was dominated by juveniles of Euphausia superba. The food bolus in N. larseni fingerlings consisted mainly of Chaetognatha, Copepoda and furcilia of Thysanoessa spp. According to the data obtained from the Ukrainian krill fishing fleet in the South Georgia area from May to August 1992, the total removals of C. gunnari and N. larseni resulting from by-catches are estimated to be 34.3 ± 8.0 and 19.8 ± 3.7 million individuals, respectively.