Observer notes (Subarea 88.1)

Results of biological data analysis of Antarctic fish species from catches of 117 bottom long-line sets in Subarea 88.1 from 15.12.03 till 10.03.04 are presented. For the first time Antarctic toothfish was found in long-line catches above seamounts of the Pacific-Antarctic Ridge to the North up to 56°S. Presence of Patagonian toothfish in spawning aggregations of Antarctic toothfish cannot lead to their intbreeding as its gonads were at the early development stages in that period. Antarctic toothfish spawning takes place above the mountains of the Pacific-Antarctic Ridge, located northward of 70°S, during the whole winter season from April till November. Spawning aggregations is only formed by mature individuals: males with body length more 100 cm, females – more than 120 cm. Gonads of individuals from the continental shelf and from the more southern seamounts (to the South of 70°S) were considerably behind in maturation and had lower GSI value. Probably, as gonads are maturing, a part of fish is migrating for spawning to the northern area of Subarea 88.1. Wide variability of Antarctic toothfish nutrition spectrum and its ability to overcome considerable overfull of depths provide for its possibility to migrate over the considerable distances. Heavy exhaustion of the most part of Antarctic toothfish individuals forming spawning aggregations was ascertained. Studies of biology of mass by-catch fish showed that Macrourus witsoni, Chionobathyscus dewitti, Cryodraco antarcticus, Chionodraco rastrospinosus was discovered in the Ross Sea the first time, Muraenolepis microps and Lepidonotothen kempi were in prespawning or spawning conditions. In ovaries of some fish there were transparent eggs, and gonads of some fish were in post-spawning condition. Sizes of yolk and hydrated eggs were given, as well as absolute fecundity of these fish species. Size composition and biological data on Patagonian toothfish from the area of Argentina hollow between 44 and 47°S were presented. Maturity length of females – 85 cm and males – 80 cm were indicated. According to our data in this area long-line fishery is based on immature fish and those matured for the first time.