CCAMLR

The ages of 252 mature female krill, collected from Prydz Bay in January 1985, were determined using length frequency analysis and the fluorescent age pigment (FAP) technique. Results of both methods indicate 6 year classes for adult krill. Correspondence between the ages determined by the two techniques is generally within one year.
The animals were also analyzed by a computerized image analysis system, which recorded a large suite of size and shape parameters. The accuracy of discriminant functions constructed to relate the image analysis parameters to age approached 90% for the ages defined by length frequency, and 52% for physiological age.

A method is proposed for estimating the biomass of swarms of Euphausia superba by catching cast off exoskeletons in quantitative net tows.

Hydroacoustic and net sampling data were used to determine the distribution and abundance of krill. In an attempt to address the effect that variability in sampling gear type may have on specific population parameters (e.g. size frequency, abundance and distribution), a multi-year comparison of these types of samp1ing gear commonly used in the Antarctic has been initiated.

Foremost in the elucidation of accurate population dynamics parameters in fish is a necessity for an errorless estimation of age. Age determination can provide basic life history information, including mortality, population age structure, and changes in individual growth. Most investigations have used annual rhythmic deposition in calcified tissues as time marks but, due ts the lack of distinct periodicity in Antarctic hydrographic conditions, age determination of Antarctic fish has proven to be difficult. It is now possible to determine the age of fish through the utilization of daily increments in otoliths, calcified tissues which may contain a large amount of biological and ecological information about a fish's past history. As part of an effort to study Antarctic fish growth and population dynamics, investigations were performed on otoliths from the Antarctic fish Champsocephalus gunnari and Notothenia rossii. External and internal examination of otoliths from by Scanning Electron Microscope (SEM) methodology revealed internal rhythmic patterns which make it possible to estimate the age of these species. Multivariate mathematical models relating age to otolith morphometrics and fish size demonstrated that age could be reliably determined from body measurements and otolith measurements. These techniques allowed us to determine that the Champsocephalus gunnari grew 55cm in 17 years and the Notothenia rossii grew 55 cm in 7 years. The lack of: the large size groups for Notothenia rossii may be indicative of over fishing and that only the younger age groups are available for harvest. It appears that length at age data determined a yearly basis for these species would provide valuable management data.

The swept area method was used to estimate biomass density changes in the stocks of five fish species Champsocephalus gunnari, Chaenocephalus aceratus, Pseudochaenichthys georgianus, Notothenia gibberifrons, and Notothenia rossii marmorata in the South Georgia area in the seasons of 1976/77-1986/87. In most of the seasons analysed, the estimates covered a near-bottom layer in about 1/6 of the area of the island shelf.
Assessment results point to considerable variations in fish biomass density, in the studied period. Estimates of fish stocks biomass ranged from 43 to 158 thous.tons. The changes in the biomass level are first of all a result of periodical fluctuations in the biomass density of C.gunnari stock. High biomass density appeared with 2-4 years intervals after recruiting an abundant year-class to the exploited stock. Biomass of other bottom species is more stable, especially in case of N.gibberifrons. Recently, an increase of the C.aceratus stock is observed and, at the same time, a gradual decline of the P.georgianus.