CCAMLR

The CPUE-based Age-Structured Production Model (ASPM) assessment of this resource by Brandão et al. (2001) is updated to take account of further catch and effort data that have become available over the past year. This leads to an improved picture of resource status compared to a year previously, but a spawning biomass nevertheless still estimated to be heavily depleted and at a level of only a few percent of its average pre-exploitation abundance. However, predictions from this assessment are at variance with the observed length frequency distributions for the fishery. It is important that the assessment model be refined to provide a consistent explanation of all the available data, as this might not only alter perceptions of the status of the Prince Edward Island resource, but also have important consequences for the assessments of other populations of toothfish in the CCAMLR region.

To provide an age-length key for use in modelling the age structure of the Patagonian toothfish stock around South Georgia, we used otoliths to estimate the age of a sample of 264 Patagonian toothfish (Dissostichus eleginoides) captured in the longline fishery. We used a thin section grinding machine to reveal a transverse plane through the otolith nucleus and between crenellations. A single reader undertook three readings of the sections, estimating age using criteria corresponding to those given by the CCAMLR Otolith Network for toothfish from South Georgia. Age estimates during the first two readings were significantly biased relative to reference ages but the third reading, after the reader had read more than 3000 otoliths, was not biased. For data pooled from this study and the South Georgia fisheries survey in 2000, estimates of the Von Bertalanffy parameters were L8 = 123.8, K = 0.10 and t0 = -2.1 for males; for females, L8 = 144.9, K = 0.085 and t0 = -2.0. Using these age data, we estimated total mortality to be Z = 0.054.

To provide an age-length key for use in modelling the age structure of the Patagonian toothfish stock around the Falkland Islands, we used otoliths to estimate the age of a sample of 1893 Patagonian toothfish (Dissostichus eleginoides) captured by trawl and in the longline fishery. We used a thin section grinding machine to reveal a transverse plane through the otolith nucleus and between crenellations. Two readers undertook one reading each of the sections, estimating age using criteria agreed at the CCAMLR Otolith Network. Age estimates by the experienced reader were unbiased relative to reference ages. However, the second trainee reader consistently over-estimated the age of younger fish, and her readings were not used in the analysis. Estimates of the Von Bertalanffy parameters were L8 = 129.3, K = 0.12 and t0 = -1.55 for females; for males, L8 = 110.9, K = 0.156 and t0 = -1.12. Using these age data, we estimated total mortality to be Z = 0.27.

Data on food and feeding of two icefish species, Champsocephalus gunnari and Chaenocephalus aceratus, were collected in the Elephant Island – South Shetland Islands region during the AMLR cruise in March 2001 with RV ‘Yuzhmorgeologiya’ and ANTXIX/3 in January – February 2002 with RV ‘Polarstern’. C. gunnari fed almost exclusively on krill (Euphausia superba) in both years. C. aceratus fed on krill and other crustaceans as well as on fish. C. aceratus smaller than 30 – 35 cm relied primarily on krill and other crustaceans while larger fish preyed predominantly on fish. They fed mainly on locally abundant fish species which were G. gibberifrons in 2001 and L. larseni and C. gunnari in 2002.

This paper reports on continuing exploration of conversion factors and the relationship between product weight & length frequency distribution in the exploratory fishery for Dissostichus spp. in sub-area 88.1 and more recently in sub-area 88.2.

A survey of Patagonian toothfish, Dissostichus eleginoides, was undertaken in Division 58.5.2 in the vicinity of Heard Island in May 2002 to provide the information for an assessment of long-term annual yield in the 2002/2003 CCAMLR season and beyond. This paper provides a preliminary assessment of yield using the assessment methods of CCAMLR, a summary of which is presented here. The estimate of biomass of juvenile Patagonian toothfish in the vicinity of Heard Island was similar to the results for 2001. The pooled length-density distribution for the 2002 survey shows that the younger year classes (ages 2 and 3) are likely to be much weaker than the current juvenile year classes (ages 4 to 8) in the survey area. The analysis also shows that larger fish seem to have left the survey area. The latest survey was used to update the recruitment series used in the assessment and resulted in estimates of recruitment being increased for some recent years. An assessment of the trend in illegal catches is expected to be undertaken at the Working Group on Fish Stock Assessment, including projections for the remainder of the season. Thus, a revision of the assessment provided here is expected to be needed following that work. The results indicate that the long-term annual yield based on the revised recruitment estimates is expected to be around 2 910 tonnes for 2002/2003 CCAMLR season. This result is slightly greater than for the 2001/02 season because of the revision in the recruitment series. The time-trend in spawning biomass, fishing mortality and recruitments arising from this assessment are presented.

CCAMLR currently establishes catch limits each year for Patagonian toothfish, Dissostichus eleginoides, that can be sustained over the generation time of the species, maintaining the population at a productive level with only a small chance of become depleted. The increasing levels of illegal, unregulated and unreported (IUU) fishing for toothfish in the CCAMLR area threatens the success of CCAMLR achieving ecologically sustainable fisheries as well as threatening the status of populations of this species. As a result of IUU fishing, the catch limits set by CCAMLR are being reduced each year to compensate for the effects of historical levels of IUU catches. To date, the rate of reduction of the legal catch limits does not seem to be commensurate with the rising levels of IUU catches. This paper explores the consequences of different rates of IUU fishing to the legally-binding TACs set by CCAMLR. The scenarios explored are with IUU annual catch at 0.33x, 1x, 2x and 4x a legal catch limit derived from an assessment based on the 2001 WG-FSA assessments, which is approximately 3 000 tonnes. The IUU catches are applied with the legal catch limit being adjusted each year after the IUU catch and the legal catch were combined in the catch history and a new long-term sustainable annual catch was estimated using the GYM and applied as the legal catch limit for the following year, assuming no future IUU fishing. If there was no IUU fishing, the long-term sustainable annual yield is set according to the escapement part of the decision rule. With fishing at levels greater than the long-term sustainable yield because of IUU fishing then the threat of depletion is increased and the legal catch limit needs to be reduced following each year that the total catch is above the sustainable levels. The closure of the legal fishery occurs when the spawning stock has been almost depleted to 20% of the pre-exploitation median biomass with a high probability of being depleted during the future projection period. Thus, low levels of IUU fishing may be tolerated, but only in the short term, while the spawning stock is above the target status of abundance. A longterm sustainable fishery requires that IUU fishing be at least reduced to levels that are much less than the longterm sustainable annual yield estimated using the CCAMLR assessment process. Continued IUU fishing at the rates reported by CCAMLR in 2001 will result in a closure of the legal fisheries in the Indian Ocean within the next 12 years because it is in excess of the estimated long-term sustainable annual catch level. The rate of reduction of the legal TAC is low because the effects of IUU fishing are averaged out in the assessment process over 35 years, assuming no more IUU fishing takes place following the assessment. The consequence of IUU fishing is a precipitous decline in the legal TAC once IUU fishing has mined the stock to a point that there is a high probability of the stock becoming depleted during the future projection period. Consequently, action to control IUU fishing would be too late if it was delayed until there was a significant reduction in the long-term annual yield obtained in the assessment process.

This paper describes the changes and development of a number of software packages developed by the Australian Antarctic Division (AAD) that are relevant to the CCAMLR Working Group on Fish Stock Assessment. The software includes the Generalised Yield Model (GYM), Fish Heaven and CMIX. Copies of the software along with associated files such as manuals and example -sets will be available through the secretariat as well as the AAD.

This paper describes and studies the very first data about the fishery of the toothfish Dissostichus elegjnoides , obtained by a Scientific Observer from DINARA on board of the uruguayan F/V “Viarsa I”, in the eastern Indian Ocean (FAO Statistical Area 57). The fishing trip was performed from the 13 of april to the 24 of june 2002.
It was determined five zones by the F/V “Viarsa I” fishing operative. Different fishing-yields rates were applied to the data and it was determined that the defined E and D fishing zones were the most productive: 8454 Kg./day and 6766 Kg./day respectively.
The average length calculated for the sampled males was 83.77 cm and for the sampled females was 81.04 cm. The median length calculated for both sexes was 78 cm. The average weight calculates for the sampled males was 7.92 Kg. and for the sampled females was 7.53 Kg.
The majority of the sampled individuals of both sexes were determined in the Grade 4 of gonadic maturity (C, D, E fishing zones). The A and B zones corresponded with the juvenile individuals of both sexes, with immature gonads.
Rests of the same species (cannibalism), eel-cod Muraenolepis spp., grenadier Macrourus spp., and skates of the Rajidae Family were identified in stomach contents.