CCAMLR

Samples gathered from research expeditions of the longliners Medvezhy (April-June 1986) as well as Maksheevo and Mirgorod (June-July 1992) have produced new data on the biology of the reproductive part of the Dissostichus eleginoides population in Subarea 48.3. Analysis and synthesis of these data have established the bathymetric distribution patterns for different size-groups of toothfish around Shag Rocks and South Georgia. A differentiation analysis of the sex structure of the D. eleginoides population was carded out. The dynamics of the maturity structure of the adult part of the D. eleginoides population are shown for the pre-spawning and spawning periods. A preliminary assessment of the reproductive ability (fecundity) of females of the species is presented. Data are also presented on the feeding patterns of D. eleginoides sampled from longline catches. Some differences in food composition in relation to fishing depth were noted.

Samples of the squid, Martialia hyadesi, were collected aboard two Japanese squid jigging vessels carrying out commercial fishing trials at the Antarctic Polar Frontal Zone, north Scotia Sea in February 1989. The dissected stomachs of 61 specimens were classified according to fullness and the contents examined visually. Identifiable food items included fish sagital otoliths, crustacean eyes, the lappets on euphausiid first antennule segments and cephalopod sucker rings. The most frequent items in the squid's diet were the myctophid fishes Krefftichthys anderssoni and Electrona carlsbergi, the euphausiid Euphausia superba and a hyperiid amphipod, probably Themisto gaudichaudi. A small proportion of the sample had been feeding cannibalistically. Total lengths of the fish prey were estimated from sagital otolith size using published relationships. All fish were relatively small; 7- 35% of squid mantle length. Over the size range of squid in the sample there was no relationship between size of fish prey and size of squid. Similarly, when the squid sample was divided into groups according to prey categories: Crustacea, Crustacea + fish, fish, cephalopod, there was no evidence that dietary preference was related to squid size. The prevalence of copepod-feeding myctophids in the diet of this squid, which is itself a major prey item of some higher predators In the Scotia Sea, suggests that a previously unrecognised food chain: copepod - myctophid - Martialia hyadesi - higher predator, may be an important component of the Antarctic oceanic ecosystem.