CCAMLR

Hydrological conditions, the distributiion pattern of krill and characteristics of the Soviet krill fishery off the Wilkes Land and Balleny Islands in 1988 and 1989 are described. The variability of some CPUE indeces (TC/TH/PPST; TC/TFISHT; TC/TFISHT/PPST) is analysed on the basis of data obtained aboard the Soviet trawler “Kapitan Oleinichuck".
The waters off the Terre d'Adelie (130° - 150° E) are likely to be . an area of regular occurence of krill concentrations, probably the frequency of their occurence is the highest in the whole East Indian and West Pacific Anrarctic. This seems to be associated with the quasi-stationary eddy, its southern branch is expressed as the East Wind Drift. Krill in fishable concentrations occur in the form of rather layers than aggregations however the diurnal transition between these forms can take place.
The characteristics of the Soviet krill fishery off the Wilkes Land are similar to those of the Japanese fishery. CPUE indeces including mean searching time per haul (TC/TH/PPST, TC/TFISHT/PPST) are strongly influenced by the fishery tactics applied by captains, they are of limited value for the assesment of the conditions of concentrations when the vessel fishes layers of krill. The TC/TFISHT-index in our case apparently. reflects seasonal and annual changes in the krill concentrations.

A brief review of the objectives of the Convention for the Conservation of Antarctic Marine Living Resources is given along with an outline of for the evolution of management procedures for krill fisheries. Various possible elements of procedures such as reactive, predictive, and feedback management, modelling, indicator species, pulse fishing, and the use of open and closed areas and seasons are outlined. Some interim management measures are suggested which could be implemented while a more generally applicable management is being developed.

Everson et. al. (1988), Foote et. al. (1990), and Everson et. al. (1990) are all based on the same experiment and report new calculations of the target strength of krill (Euphausia superba) that propose questioning previous measurements of krill target strength and estimates of abundance derived from them. Their results can be shown to have significant weaknesses in both data used and assumptions made in calculating target strength. Whether the results of these papers are valid is critically important, given that they are being cited as a basis for increasing the estimates of krill standing stock in the Antarctic. The weaknesses in their data stem from the methods used to calculate target strength from the data and fall into three categories: 1) Errors in measurements and assumptions; 2) density dependent effects; and 3) compounding of diel effects. The possible bias in the calculations of target strength due to these weaknesses indicate an estimated 3-5 dB error due to unaccounted for directivity effects as a result of items under category 1; an estimated 2-3 dB bias due to systematic errors under category 2; and an estimated 3-4 db error due to category 3. Thus there is reason to believe that there is 8-12 db of possible error in the calculations. This is most if not all of the difference cited between their target strengths and those of other investigators at 120 kHz. These target strength calculations seem to be flawed (no correction for directivity and behavior), contain a significant density dependent bias (correlation of target strength of an individual krill on the number of krill used to measure it), and contain or are likely to contain an error due to diel behavior effects

The homogeneity of krill length composition in commercial trawl catches (hauls) was investigated by comparing length compositions from different parts of the same haul. There was no significant difference (P>0.05) in 53 out of 60 hauls. Therefore it is concluded that sampling from one part of the haul provides a reasonable estimate of length composition in the entire haul as a whole. In contrast to small variations in length composition within the same haul, variation between different hauls was most noticeable in areas where krill length compositions were bimodal.