CCAMLR

Over the last two years, discussions in WG-EMM, WG-FSA and the Scientific Committee have highlighted a need to develop an integrated work plan to develop and validate assessment methods.
WG-FSA noted (paragraph 11.3, WG-FSA 2001) that there are substantial difficulties added to the work of the assessment subgroup when new quantitative methodologies are introduced and incorporated into assessments undertaken during the time of a single meeting of WG-FSA. Issues related to the current procedures and new assessment techniques need to be introduced to the assessment subgroup and tested prior to WG-FSA. The Working Group suggested that the best way to achieve this is for the assessment subgroup to have intersessional communication to identify and discuss concerns, requirements and new methods. The activities of the assessment subgroup should be prioritised before the meeting to increase the efficiency and quality of the assessments.
This paper amalgamates the correspondence from during the year and the papers submitted to WG-FSA to provide draft points for discussion by WG-FSA on
1. materials available to WG-FSA for incorporating into assessments
2. a draft plan for assessments at WG-FSA this year, including reporting and archiving.
3. a proposed workplan for the future, including a timetable for work in the 2003 intersessional period.

Results of the inventory trawling survey of icefish carried out by Russian vessel STM-8390 Atlantida in February 2002 in Subarea 48.3 are presented. During this period, the fish were mainly foraging. Champsocephalus gunnary 22-28 cm in length at the age of 2-3 predominated on all grounds of the Subarea, except the north-eastern part. During the survey, specimens 15 cm in length at the age of 2 prevailed in pelagic catches. Peculiarity of Ch. gunnary biology in 2002 consisted in high internal fatness at low stomach fullness. On the eastern shelf part, a considerable number of pre-spawning specimens had already been detected, which was not characteristic of that month. .Total biomass near the bottom estimated by different methods is amounted to 38 – 45 thous. t.

Dynamic production models (DPM) have been proposed for D. eleginoides stock assessment in subarea 48.3. This type of the models differ from the models currently used by CCAMLR Working group on fish stock assessment as they do not require certain initial data and parameters (natural mortality, age selectivity, recruitment estimates, mean weight at age) In the calculations with DPM (with Schaefer and Fox production functions) were used: total yield for a series of years and abundance index describing interyear biomass dynamics (standardized catch per unit effort for 1986- 2001) and fishing effort estimates by years of fishing.
Both models showed that the D. eleginoides stock status at the initial period of intensive fishery was at the level of 22-24 thousand tons. In 1989-1990 stock size increased (to ~31 thousand tons) and then gradually declined, having reached the minimu m size of 12 thousand tons in recent years.
The trends in biomass dynamic estimated by DPM are very similar with trends from dynamic age-structured production model ( ASPM) (Gasiukov, Dorovskich, 2000): DPM and ASPM display more then twofold decline of total biomass since 1990 until now.

Samples of Chaenocephalus aceratus were collected during a trawl survey carried out around the South Shetland Islands in the austral summer 2002 (January-February). Fish were caught by commercial bottom trawl fishing down to 500 m depth, using a stratified randomized sampling design. As observed in other recent surveys within the same area, C. aceratus represented one of the predominant species. Overall, 357 specimens ranging from 13 and 67 cm (TL) were selected for the present study. Ages were estimated by counting annuli present in the sagittal otoliths, exposed by grinding and polishing along their sagittal plane. To estimate the precision of age data, we compared blind readings by readers from different institutions. The age range was 1-17 years for females and 1- 15 years for males. Von Bertalanffy growth curves were fitted to the estimated age-length data for each sex. The estimated values of asymptotic length L??(cm) and K (year-1) were respectively 79.8 and 0.07 for females and 60.0 and 0.09 for males. The growth performance index ranged between 2 and 2.5, similar to that reported in other icefish. Sexual maturity was attained by females and males at about 10 and 9 years old respectively, at about 60 % of their maximum estimated age. These results are compared with age and growth data available in the literature for C. aceratus, and discussed in the light of recent commercial exploitation.