CCAMLR

Some biological peculiarities of E. carlsbergi from the Antarctic and notal areas of the Southern Ocean Atlantic sector have been studied on the basis of the data for 1987-1989.
Mean length of fish from the Antarctic area increased while drifting eastward in the Antarctic circumpolar current waters. Fish specimens from 62 to 97 mm long were registered in catches. About 95% of specimens analysed were at age 2 to the west of 35°W and 3 yr old specimens , the portion of which made up to 40% in catches, occurred in much high amount to the east of 30°W.
In the notal area the length of E. carlsbergi reached 103 mm. Fish from older age groups (3 and 4 yr old) constituted about 85% of total amount, with fish at age 1+ (to 75%) being noted in separate catches.
Essential distinctions in a nature of the "fish length/fish weight” and "fish length/otolith weight" relationships between males and females from the Antarctic and notal areas have been elucidated.
Growth rate in the notal area was somewhat higher,with the highest increment being observed at the 1st and 2nd years of life. Limiting age for fish from the notal area is, probably, 5 years.
E. carlsbergi investigated in the Antarctic waters occurred to be immature. Spawning was registered in summer only in the notal area.Over 50% of specimens become mature at the 3rd year of life at 85-89 mm length.
Determined differences of the length–age and length–weight compositions, as well as the rate of growth and maturation in comparable groupings indicate a possible expatriation of E. carlsbergi to the Antarctic area from the region of reproduction of the notal one.

A subject of the present study is Electrona carlsbergi from the Atlantic sector of the Southern Ocean. Results from histological examination of gonads are presented. From materials available it has been ascertained that Electrona carlsbergi breeds in the notal zone. The ripening of females begins at body length of 76-78 mm. Vitellogenesis is asynchronous. Vitelline eggs have a diameter from 150 to 650μm, and it reaches 900μm in hydrated oocytes. Maturation of ovaries is continuous, the spawning is serial. The spawning season is extended and coincides with the summer-autumn period.

Acoustic surveys carried out in summer and autumn periods of 1987-1989 estimated the biomass of myctophids in the Atlantic sector of the Southern Ocean over the region between 48° and 56°S and from 8° to 48W at about 1.7 mill.t. Over the larger part of the surveyed area the fish were sparse, their dense concentrations composed predominantly of one myctophid species Electrona carlsbergi occurred over only restricted areas. The bulk of the biomass has been reported from the region of the Antarctic Convergence.

In the summer-autumn period E. carlsbergi fed mainly on copepods. Daily food intake measured using various methods ranged from 3.7 to 5.6 % of fish body weight. The amount of food consumed by E. carlsbergi during the year in the southern regions of the Antarctic Convergence is about 15 times its own weight.

Catches of Champsocephalus gunnari from the Kerguelen Shelf and Skiff Bank stocks were re-calculated from those used by the Working Group on Fish Stock Assessment in 1989 using length-frequency data for the years 1981 to 1990. Cohort analysis yielded a Stock Biomass of 22 711 tonnes in 1988 for the Age 2 Kerguelen Shelf stock, an order of magnitude lower than that calculated from a biomass survey in 1988 by the USSR. This biomass is consistent with that from previous cohorts and indicates a possible declining trend in the abundance of this stock.

Based on a tentative adjustment of catches of Notothenia gibberifrons previously reported as ‘Pisces nei’ an attempt is made to reconstruct the fishery on that species between 1977/78 and 1985/86. Stock size until the mid 1980s seemed to be more reduced than previously assumed. The current state of the stock is unknown.

A declining trend observed in the abundance of fjord fish of the species Notothenia rossii marmorata and Notothenia gibberifrons from two localities of South Shetland Islands, is analyzed by a nested ANOVA and demonstrated as significant. The material studied was obtained with trammel nets at Potter Cove, King George/25 de Mayo I., from 1983 to 1990 and in waters around Half-Moon I., Moon Bay, in 1989. The analysis was based on the proportion of catches of the mentioned species in relation to Notothenia neglecta, a species with similar ecological habits in the fjords. Comparison with analogous published data obtained at close localities in the 60’s and 70’s, also shows a marked declination. This phenomenon in the area might be explained as a consequence of the depletion of the stocks due to commercial exploitation.