CCAMLR

The underwater vessel noise levels perceived by the echosounder EK-500 transducers of three Russian research vessels have been presented. These data have been compared to the estimate of the underwater noise level, produced by the Icelandic R/V B.Saemundsson..
Underwater noise level perceived by the echosounder transducer versus its operation frequency and vessel speed has been analyzed. It has been shown that the level of underwater noise produced by vessel is an important technical property to be taken into account in assessment of such parameters of Acoustic Sampling Protocol as TS and Sv thresholds and vessel’s speed . The interrelation between choice of TS and Sv thresholds and vessel speed when echosurveying has been emphasized.
It has been shown that a difference between the underwater noise levels of vessels participating in multiple-ship survey, cannot provide for the choice of desirable speed of the vessels with the unique given level of TS and Sv thresholds used by all vessels. The importance of the research vessel underwater noise level has been discussed when standardizing acoustic data collection from multiple-ships like during a multinational effort to synoptical survey the Area 48 .

An acoustic survey, designed to study the distribution of shore-breeding, marine predators and their pelagic prey, was carried out in 1986 around the western end of South Georgia. This paper describes how this acoustic data has been used to estimate krill biomass of part of the original survey area as part of an interannual study. The radiating transect design gave increased sampling intensity in the shallower part of the area, so a method of post hoc stratification has been devised to generate sub areas with more even sampling. The results highlight the importance of the shelf slope area for krill.

We update in this paper the previously reported model for the Antarctic fur seal Arctocephalus gazella population breeding at Cape Shirreff and San Telmo Islets (SSSI No.32), Livingston Island, South Shetland, Antarctica. We also discuss the current reliability of the model and related population parameters to an environmental index (the Southern Ocean Oscillation Index - SOI).
Two fur seal censuses were developed at Cape Shirreff during 1998/99, but we could not census the San Telmo Islets. In this regard, we had to model the population at the latter site, in order to have a complete estimate of the population. From this, we estimated an overall increase of 17% in the total population, including in this figure a 10% increase in pup production in the SSSI No.32.
Current population estimates are reaching modelled values of the carrying capacity of the environment (K). This might not be correct due to the restrictions of the simple model used, and the weighted effect of the continuos data set during these last 8 years, and the scattered historical data.
Further evidence that the breeding population of A. gazella is affected by the El Niño Southern Oscillation phenomena might be given by the intrinsic rate of population growth (r) when compared with Southern Oscillation Index (SOI) values.
The intrinsic rate of increase of a population of top predators, in this case A. gazella, can probably predict large scale environmental phenomena if the population is under a monitoring programme, and may have an interesting effect on resources management policies.

The paper introduces several approaches to assessment of hydrological situation in the Atlantic sector of the Southern Ocean (the South-West Atlantic). The analysis of the SST maps suggests that hydrological factors depend on the intensity of two currents, the Antarctic Circumpolar Current and the Falkland current The paper shows correlation between a certain hydrological situation and fishing for squid Illex argentinus.

In the austral summer of 1995/96, 25 southern elephant seals, Mirounga leonina, were stomach lavaged at Stranger Point, King George Island, South Shetland Islands. Cephalopod remains were present in 72% of the individuals sampled (n=18). Seven species of squid and 3 of octopus were identified. Overall, the squid species Psychroteuthis glacialis was by far the most important prey in terms of numbers (77%), biomass (80.8%) and frequency of occurrence (94.4%). Next in importance in terms of mass in the diet of females was the squid Alluroteuthis antarcticus (7%) whereas the octopodid Pareledone charcoti was in the diet of males (13.2%). Females preyed on a wider variety of squid taxa than males (7 vs. 3) but octopodids occurred only in stomach contents from males. The predominance of P. glacialis in the prey of the South Shetland elephant seals can be explained by the southerly location of the foraging areas of this population compared to South Georgia, Heard and Macquarie Islands, where the diet of Southern elephant seals has previously been analyzed. P. glacialis is the predominant squid in waters close to the Antarctic continent.

We requested data and information for further developing draft standard methods for recording sea-ice cover viewed from a CEMP site (Index F1), local weather at a CEMP site (Index F3) and snow cover at a CEMP site (Index F4). The information at hand was reviewed, and a revised approach to finalising the methodology for calculating these indices is proposed.

Work undertaken during the intersessional period has enabled better use of the krill fishery data, and a comparison between the three existing indices of fishery-krill-predator overlap used by CCAMLR (catch in the Critical Period and Distance [CPD], Agnew-Phegan index, and Realised Potential Overlap [RPO]) and the Schroeder index. The Agnew-Phegan and Schroeder indices were also compared at nine levels of spatio-temporal resolution and using normal, exponential and uniform foraging distributions.
Only catch in the CPD can presently be used to estimate overlap in areas other than Subarea 48.1. The catch in the CPD and the Agnew-Phegan index were closely correlated, as were the RPO and Schroeder index. All indices exhibited similar broad inter-annual trends over the period 1983 to 1998, indicating reduced overlap in Subarea 48.1 after 1990. The RPO and Schroeder index indicated a greater increase in the level of overlap in recent years (1995-98) than estimated with either the catch in the CPD or the Agnew-Phegan index. The type of foraging distribution and level of spatio-temporal resolution produced small difference in the values of the Agnew-Phegan and Schroeder indices, but had little influence on inter-annual trends. Increasing the level of resolution of the model, and in particular the spatial resolution, resulted in lower overlap between the krill fishery and the krill predators, and lower values of both the Agnew-Phegan and Schroeder indices.