CCAMLR

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.

In an investigation of the age structure of a population of Notothenia coriiceps Richardson at the South Orkney Islands, Antarctica, the microstructure of otoliths was examined. Progress is reported on a method used for processing large numbers of otoliths using a scanning electron microscope (SEM). Compared with previous SEM techniques, which normally prepare otoliths individually for viewing, this allowed larger sample sizes to be examined. Compared with similar light microscope techniques, this method gave enhanced resolution particularly for discerning edge structures, and thus may facilitate present methods of ageing fish populations, especially for fishery work in the Antarctic where otoliths are often small and difficult to interpret using conventional techniques.

To validate the timing of annuli in otoliths of immature Notothenia coriiceps Richardson. a time-series of samples were taken over a complete year. Light and scanning electron microscopy (SEM) techniques were used to examine the structure of sectioned otoliths. Six growth regions were identified in the otolith sections and micro-increments were also evident. The timing of growth and annual nature of annuli revealed by SEM were demonstrated. Annuli revealed by SEM and light microscopy techniques were shown to correspond, supporting the hypothesis that annuli visible by using light microscopy represent one year. Using SEM the potential errors due to light illumination artefacts and the pseudo-hyaline features could be avoided.

Observations on abundance of by-catch fishes were made during the austral winter months of 1992 (from July 9 to August 3) on board F/V No.3 and No.5 Chiyo Maru in the vicinity of the South Georgia Island. Among 74 net hauls examined, a total of 66 specimens of fishes belonging to 3 species were found in 20 trawl catches.
Among by-catch fishes, juvenile Lepidonotothen larseni was the most abundant (62 specimens; 93.9% in number; 58.9% of total weight of by-catch fish). Standard length (SL) of L. larseni varies from 32.4 to 52.1mm (average 44.5mm; mean 45.3mm). Three specimens of juvenile Champsocephalus gunnari ranging 80.5 to 88.3mm of SL and one adult specimen of Electrona antarctica (72.1mm of SL) were also found, but no other fish species was recognized in our by-catch samples. The abundance of fish in our krill catches was relatively low (less than 52 individuals and 43.68g per 100kg of krill) in comparison with some data reported previously.

During the 6th Antarctic Expedition of R/V Kaiyo Maru (1990/1991), observations on the occurrence and abundance of fishes in a total of 102 pelagic hauls for the Antarctic krill were made.
Of the 102 net hauls, a total of 104 fishes belonging to 4 families and 16 species were captured in 25 tows. Juvenile Lepidonotothen larseni was the most abundant (46 individuals; 44.2% in number) and post-larval Cryodraco antarcticus was the next (14 individuals; 13.5% in number). The standard length of L. larseni ranged from 41.4 to 50.9ram (average 46.8mm; mean 46.6mm). Among the notothenioid fishes collected, only two adults (one specimen of Gobionotothen gibberifrons and one channichthyid fish - specimen lost on board) were included. Bottom depths of the stations where notothenioid post-larvae and juveniles were caught were less than 1000m deep. On the contrary, bathypelagic groups of the Myctophidae and Paralepididae were collected at the 11 offshore stations which bottom depths were deeper than 2000m.
In contrast with other previous data, present results (less than 36 individuals per 0.5 hour haul) show relative low abundance in pelagic catches for this region.