CCAMLR

An updated descriptive analysis of the toothfish tagging programme carried out in Subareas 88.1 and 88.2 since 2001 is presented. Tag-release and tag-recapture data are presented for both toothfish species for the Ross Sea (Subareas 88.1 and SSRUs 88.2A–B), and SSRU 88.2E for New Zealand vessels. A total of 4903 Antarctic toothfish have been released and 89 recaptured, and 443 Patagonian toothfish released and 9 recaptured. For the last two years, when tagging has been part of the Conservation Measure, New Zealand vessels have tagged between 1.0 and 2.77 toothfish per tonne of catch. Tagging rates by area over the past three years have been in the same proportion as the catch by area. However, recapture rates have tended to be higher in the northern and eastern SSRUs 88.1C and 88.2E.
The maximum movement of Antarctic toothfish from the New Zealand data set has been about 200 km. However, most (80%) Antarctic toothfish have moved less than 50 km. Consequently, nearly all fish have been recaptured from the same SSRU where they were released. The mean size of tagged Antarctic toothfish has increased since 2001, but is still smaller than the mean size of fish taken in the commercial catch. Larger toothfish (>35 kg) are difficult to tag without significant damage to fish, and there is be a trade-off between maximising size of released fish and minimising tagging mortality. Growth rates of Antarctic toothfish that have been at liberty for 2–3 years have averaged 5–7 cm per year, which is consistent with growth rates predicted from the von Bertalanffy growth curve.

This report outlines a Bayesian sex and age structured population stock assessment model for Antarctic toothfish (Dissostichus mawsoni) in the Ross Sea (Subareas 88.1 and SSRUs 88.2A–B). A range of model sensitivities were examined, with the base case assuming the Ross Sea fishery as a single homogeneous area (single-area) with catch removals from three spatially based fisheries (shelf, slope, and north).
Model fits to the data were adequate, with the tag-release and recapture data providing the most information on stock size. Monte-Carlo Markov Chain (MCMC) diagnostics suggested some evidence of non-convergence, particular in the declining right-hand limb of the fishing selectivity parameters. However, multi-chain comparisons and sensitivities with fixed selectivity ogives suggested that this would have little impact on the estimates of key model parameters and yield estimates.
MCMC estimates of initial (equilibrium) spawning stock abundance (B0) were 69 400 t (95% credible intervals 47 700–111 900 t), and current (B2005) biomass was estimated as 88% B0 (95% C.I.s 83–93%). Estimated yields, using the CCAMLR decision rules, were estimated to be 2964 t although continued catch at current levels (3207 t) would not be expected to breach the 50%B0 threshold until 2029.

The Ross Sea toothfish fishery has operated during the Antarctic summer (November–May) since 1997 in CCAMLR Subareas 88.1 and 88.2. Previously, standardised analysis of toothfish CPUE (catch per hook) have been carried out in 2004 calculated CPUE indices for the 1997–98 to 2003–04 fishing years in Subarea 88.1 and 88.2. This report revises and updates the previous analysis with the addition of data from the 2005 season for the Ross Sea (Subarea 88.1 and SSRUs 88.2 A–B) using data sets based on (a) all vessels and (b) the two main New Zealand vessels that have been in the fishery over most of the period. We estimate indices using both lognormal generalised linear models and a Tweedie mixed model, in which data were modelled using the methods described by Candy (2003)
The variables included in the analysis appeared reasonable and were consistent between the models presented here and CPUE analyses for previous years. The yearly indices were relatively stable between 1998 and 2003, with a decline in 2004, and a sharp increase in 2005. Possible explanations for the decline in 2004 were described by Phillips et al. (2004) as gear conflict and competition between vessels to set lines, in addition to extreme ice conditions that limited where lines could be set. None of these factors were believed to be important in 2005.
Investigation of additional explanatory terms included an index of ice cover and an index of vessel crowding. Neither of these terms was found to be significant or explain the decline in 2004 or the increase in 2005. Lack of a balanced experimental design and possibly the choice of parameterisation of the variables are likely to be the reasons why neither of these terms were found to be significant.

This report outlines a Bayesian sex and age structured population stock assessment model for Antarctic toothfish (Dissostichus mawsoni) in SSRU 88.2E. The model structure was assumed to be the same as used for the Antarctic toothfish in the Ross Sea (see Dunn et al. 2005b), except that catch removals were modelled as a single fishery.
Model fits to the data were adequate, with the tag-release and recapture data providing the most information on stock size, but with the catch-at-age data excluding preventing very low estimates of stock size. Monte-Carlo Markov Chain (MCMC) diagnostics suggested some evidence of non-convergence, particular in the declining right-hand limb of the fishing selectivity parameters.
MCMC estimates of initial (equilibrium) spawning stock abundance (B0) were very uncertain, with the median estimated as 7720 t (95% credible intervals 3760–22 240 t), and current (B2005) biomass estimated as 91.8% B0 (95% C.I.s 83.1–97.1%).
Estimated yields, using the CCAMLR decision rules, were estimated to be 670 t. However, as the fishing selectivity was estimated to be to the right of the maturity ogive, there was a significant biomass of mature, but ‘invulnerable’ fish in the projection period. Moreover, the mean catch that could actually be taken under this scenario was 450 t. Hence, two revised methods for assessing risk are also considered. The first assumed that the future fishing selectivity was equal to the maturity ogive, and hence the yield was calculated as 273 t. The second used the model estimate of the vulnerable biomass as the reference biomass in the risk evaluation, and hence the yield was calculated as 218 t.

A survey of Patagonian toothfish, Dissostichus eleginoides,was undertaken in Division 58.5.2 in the vicinity of Heard Island in June 2005 to provide the information for an assessment of short-term annual yield in the 2005/2006 CCAMLR season. This paper provides a preliminary assessment of yield for the area of Division 58.5.2 to the west of 79°20’ E using standard CCAMLR methods. It also considers the sensitivity of the assessment to (i) further consideration of the survey series and the sensitivity to exclusion of observations of older cohorts in recent surveys, (ii) implementation of revised growth parameters, including the use of a length-at-age vector, (iii) consideration of a vulnerability function for the future projections based on full selection of adult fish, and (iv) consequence of reducing the range of natural mortality from 0.13-0.2 to 0.13 – 0.165, consistent with slower growth rates of fish.

The exploratory fishery for Antarctic toothfish (D. mawsoni) has been operating for eight years in Subarea 88.1 and for four years in Subarea 88.2 with a large amount of data collected on toothfish and the associated bycatch.
The 2005 D. mawsoni catch was the highest on record with a total of 3477 t against a catch limit of 3625 t. The catch limit was almost reached in Subarea 88.1 and exceeded in Subarea 88.2. D. mawsoni was the dominant catch in all 11 SSRUs fished. The main bycatch species were rattails, which contributed 12% of the catch, and skates which contributed to about 2% of the total catch1.
Comparison of the location of fishing effort with ice distribution over the past six years has clearly demonstrated the strong influence of ice on this fishery. In 2001, 2003, and 2004, ice conditions were particularly bad and fishing was restricted to suboptimal areas. However, in 2005, ice conditions were very good, allowing vessels access to most of the main fishing grounds in both Subareas. This resulted in the closure of all SSRUs due to catch limits for toothfish, or bycatch limits for rattails, being reached by 18 March 2005.
The change in fishing patterns between seasons is reflected in the mean length and age composition of the catch. During the development of the fishery there has been a steady increase in depth fished, which peaked in 2003, but decreased slightly in 2004 and 2005. This is reflected in the mean length and age composition of the catch, which also declined slightly in 2004 and 2005.
1 Note that this does not include skate released at the surface.

Results of samples’ processing fixed from Sub-area 88.1 in the 2003-2004 season aboard f/v «Yantar» operating in the Exploratory Fishery were presented.
According to the results of investigation of oocytes’ size composition and histological researches of ovaries at different maturation level it was ascertained that intermittent oogenesis type and synchronic development of the nearest spawning oocytes portion is characteristic of Antarctic toothfish. Absolute calculated fecundity was about average 1 million eggs and relative one was about 25 eggs per 1 g of body weight.
It was confirmed that the predominant part of pre-spawning individuals was concentrated over isolated sea mountains to the north of 70° S. It was demonstrated that some part of females participated in spawning not every season and missed spawning.
Data on fecundity of some by-catch species are given. State of Patagonian toothfish gonads’ maturity in Argentina Sea in March, 2004 is discussed.

The Patagonian toothfish (Dissostichus eleginoides) has been fished in the Kerguelen Islands zone for 20 years, firstly with trawlers and more recently with longliners. It is the oldest fishery of the Indian sector of the Southern Ocean. However IUU fishing has appeared in 1997. A GLM analysis has been performed from the statistical data of the legal fishery to assess the factors affecting the catch per unit effort (CPUE) both from the trawl and the longline fishery. The recent trends show a decrease of the CPUE, indicating a probable local overfishing. The bathymetric spreading of the fishery seems to have partially occulted this situation. In addition some biological facts (such as depth distribution, spawning date and place, and movements between geographical sectors), of the adult part of the population have been obtained from a scientific programme conducted by the fishery observers onboard the fishing vessels.

This document indicates our intention to get admission for adopting new longline system instead of Spanish longline system to exploratory longline fisheries for Dissostichus spp. in Subarea 48.6 in 2005/06 season, showing difference between two systems by two figures, and explaining the reason why we want to adopt new system with results of bottle test.

The First Meeting of the Advisory Committee to the Agreement on the Conservation of Albatrosses and Petrels was held in Hobart from 20-22 July 2005. This meeting followed the First Session of the Meeting of the Parties, held in Hobart from 10-12 November 2004.
Eleven Parties have ratified the Agreement of which six were represented at the Advisory Committee meeting. In addition three range states were represented as well as observers from CCAMLR, Birdlife International and SCAR.
The meeting examined issues associated with the establishment and operation of the Agreement Secretariat; noted reports from Parties and Signatories on activities relevant to the implementation of the Action Plan; reviewed reports from its Working Groups and agreed to establish a Working Group on Breeding Sites.
The meeting examined a number of papers submitted in relation to the issue of incidental mortality in fisheries. It was agreed that engagement with RFMOs was fundamental to improving the conservation status of many albatross and petrel populations and that ACAP should seek observer status at relevant RFMO meetings; FAO COFI; Regional Fisheries Bodies; and International Coalition of Fisheries Associations.
The meeting also noted the considerable work that had been done by CCAMLR to reduce seabird bycatch in CCAMLR waters and looked forward to continuing with this spirit of cooperation by maintaining a close working relationship between CCAMLR and ACAP.