CCAMLR

The paper considers the determination of time of breeding of five species of Antarctic Euphausiids. The original and literature data on age composition of larvae gave the possibility to calculate the dates of the beginning, termination and periods of high and the most intension of spawning. In the waters of different origin and on different latitudes euphausiids begin to spawn in a usual succession (Makarov, 1979): Euphausia triacantha - E. frigida - Thysanoessa macrura - E. crystallorophias - E. superba. The spawning of each species begins later in waters of high-latitude origin. The same connection exists for the period of the most intensive spawning. The termination of spawning in the waters of high-latitude origin is earlier then in the waters of an other type. The correlation with a geographical position of a region (latitude) is obvios for the beginning and maximum of the spawning while for the termination it is obscure. All the species of Antarctic Euphausiids exept E. superba are spring-spawning while the last is summer-spawning.

The paper considers peculiarities of krill fishery conducted by a krill fishering and processing vessel producting krill meat. The vessel operated in the Commonwealth Sea, the Cosmonaut Sea and in twi Scotia Sea areas (off South Orkneys and off South Georgia) from February to June 1988. In all four areas the average catch per hour was maintained at the same level of 5-8 t to permit full utilisation of raw krill for processing. The catsh size was regulated by varying haul duration on yhe basis on echo recordings. Changrs of fishing areas were sometimes caused by weather conditions but yhe chif cause was tthe size composition of krill in the catches. Preference was given to larger krill. The density of krill in aggragtions usually remained at a high level and was a less important cause of area changes.

Though South Georgia and Bouvet Island are located at the same latitude, the growth and maturation rates as well as the average minimal sizes of E.superba are appreciably higher in the former than in the latter area. This is attributed to milder climatic conditions and better food supply in the South Georgia area as compared to Bouvet Island. The differences in the growth and maturation rates of E.superba between these two areas persist with a change of climatic epochs. During the warmer climatic epoch maturation in both areas begins earlier and stops later than during the colder epoch. Two spawning peaks are observed during the warmer and one peak during the colder epoch.

Analysis of original and literature data for the past 10 years pertaining to the region -of the Antarctic Penunsula and adjacent waters points to a relationship between the distribution of krill and the waters of two major circulation systems - those of the Weddell Sea and the Bellingshausen Sea inhabited by separate subpopulations of the species. The latter are predominant in the region while the proportion of the Weddell Sea krill increases eastward, primarily in the Bransfield Strait but also off the Mordvinov Island. Seasonal coastward migrations (Siegel's suggestion) may actually result from the fact that waters of each of the two major modifications carry out krill into the eastern part of the region at different times. Isaacs-Kidd trawl surveys yielded krill biomass values of 1233±41% and 1708±30% thousand tons in March and December-1984 respectively for the area south of 60°S between 60 and 52°W. The frequency of occurrence of krill aggregations in the area between 75 and 52°W was estimated. For this area, the 1984 survey data yielded krill biomass estimates of 3.27 to 7.89 million tons.