By-catch of juvenile Antarctic fish from krill (Euphausia superba Dana) fisheries in the South Georgia area, in 1992

Discussed in this paper is an investigation on juvenile antarctic fish caught during krill fishing by the BAT GrigOly Kovtun in the region of the South Georgia Islands during the period May-June 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 considering all krill tows and 45.5% when only tows made in shelf waters were considered. Juvenile fish abundance, normalised to 1 t of krill, ranged from 700 to 18 900 individuals. In the case of C.gunnari, average values were 966±225 ind/1t krill and 2434±579 ind/1t krill for all trawls and for shelf trawls, respectively. Similarly, for N.larseni the corresponding averages were 557±103 and 1388±248.
The mean standard length of C.gunnari was 73-80 mm in May-June and 97 mm in late July. The mean growth rate of this species over this period is estimated at 0.35 mm per day. In May-June N.larseni juveniles were represented by fingerlings (mean length of 42-47 mm) and yearlings (72-73 mm). In late July the mean length of fingerlings increased to 50 mm. The mean daily length increase in N.larseni is estimated at 0.09 mm.
Juveniles of Euphausia superba dominated by mass the diet of both C.gunnari fingerlings and N.larseni yearlings. The food ball in N.larseni fingerlings consisted mainly of Chaetognatha, Copepoda and furcilia of Thysanoessa spp.
According to the results obtained from krill fisheries of the Ukrainian fleet in the South Georgia area (35 500 t within the period from May to August) the total elimination of C.gunnari and N.larseni is estimated to be 34.3±8.0 and 19.8±3.7 million individuals, respectively.