CCAMLR

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.

The northern geographical distribution of the toothfish Dissostichus eleginoides, reaches the Exclusive Economic Zone of Uruguay. The species was firstly cited for the uruguayan waters by Devincenzi in 1924, and it is usually found by fishing trawlers between 900 m and 1200 m of depth, along the submarine continental ridges. Since 1997 some fishing vessels, like the F/V “Viking Sky”, started to capture the toothfish using conic bottom fishing-traps with sardine and squid frozen bait.
The F/V “Viking Sky” performed this fishing trip between the 2 of september to the 11 of october of 2001, with a Scientific Observer from DINARA on board. The ship looked for fishing zones both in uruguayan and international waters (FAO Statistical Area 41). Three different fishing zones were geographically determined:
Fishing zone South Latitude West Longitude
Northern Zone I 37.57 54.08
37.48 53.43
Southern Zone 42.17 57.57
42.51 58.33
Northern Zone I 37.42 53.40
37.09 53.42
The Southern Zone had the best fishing-yield: 5,7 Kg./trap/day; while the Northern Zones I and II had a very similar but inferior yield: 4,96 Kg./trap/day and 5,38 Kg./trap/day.
The average, modal and median length calculated for each sex were the following:
Males Females
Average length 86.18 cm 87.25 cm
Modal length 90.00 cm 85.00 cm
Median length 89.00 cm 86.00 cm
The majority of the sampled individuals of both sexes were determined in the grade 2 of gonadic maturity (84% of males and 89% of females), which means that most of the capture were juvenile. The selectivity of the fishing traps were determined in 59 cm of fish length, as the minimum size captured.
The deep-water lobster (Crustacea) Thymops birsteini; and grenadiers Macrourus spp. were captured as incidental fishing by the bottom traps.

The icefish fishery on the Kerguelen shelf has been stopped after the1994/95 fishing season when 3889 tonnes of Champsocephalus gunnari were landed (see CCAMLR statistical bulletins) because yields were not enough high and the lucrative fishery of Patagonian toothfish Dissostichus eleginoides deverted fishermen from these specific shallow fishing grounds. However to follow the situation in the area the fishery licences for trawlers have been linked to the obligation of conducting some experimental cruises in the traditionnal area of fish aggregations. Such cruises occur regularly with two trawlers from 1996/97 to 2001/2002, the last season of trawling in the Kerguelen EZ. Preliminary results do not show an increasing of the icefish’s abundance in the surveyed area and biomass seems very low. It is a different situation comparitively to the Heard islands stock where biomass allows catches. This situation is not clearly explained and various hypothesis are proposed: no recovery in a too depleted stock, bad recruitement or emmigration in relation to the ENSO 1998 effect in the vicinity of the islands, increasing of predation by fur seals Arctocephalus gazella growing the population. Other analysis (total and species by species biomass, importance of the by -catch in the area) will follow this preliminary analysis.

Kirkwood and Agnew (2001, paper WG-FSA-01/48) proposed an ad hoc method for estimating selectivity curves for toothfish taken by longliners around South Georgia and Shag Rocks over the period 1995 – 1999. This method was applied by WG-FSA-01, with minor amendments, to estimate annual age-specific selectivities for the years 1995 – 2000 for input to the GYM assessment. In this paper, I propose a revised method for estimating the selectivities based on an assumption that the proportions of the total CPUE in an area for a particular length class that are taken in different depth zones are Beta-distributed. This removes some of the ad hoc nature of the former estimation method. The method is illustrated by application to data for 1995 – 2000.

This manual provides the documentation required for running the spatially-explicit population simulation software, Fish Heaven, which is available through the secretariat as well as the AAD.

This manual provides the documentation required for running the Generalised Yield Model (GYM) and its graphics user interface, which is available through the secretariat as well as the AAD.