CCAMLR

An outline is provided on data and analyses which would be required to improve the knowledge of the stocks and improve the Scientific Committee’s ability to provide less controversial management advoice. However, a level of uncertainty higher than in fish stock assessment in other parts of the World Ocean (e.g. the North Atlantic) has to be accepted and to be taken into account for fisheries management. As a result. advice provided by the WG FSA can rarely be unequivocal, albeit it has to be considered as ‘the best scientific evidence currently available’.

This paper discusses the impact bottom trawling may have on Antarctic benthos. This problem has not been dealt with neither by the Antarctic Treaty System nor by CCAMLR so far.

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.