CCAMLR

This project involved the large-scale deployment of electronic monitoring (EM) systems on the 2002 British Columbia halibut longline fishery to evaluate the feasibility of EM as an alternative to observer-based at-sea monitoring. EM systems were deployed on 59 regular halibut fishing trips involving 19 fishing vessels, providing about 700 usable sets, 1,000 hours of imagery, and 350,000 observed hooks. Catch items identified by EM represented over 60 fish, invertebrate or seabird species or species groupings, and the 15 fish most abundant species accounted for 98% of the catch. Data from fishing trips where EM and observers were deployed (about 55% of trips) were compared by total overall catch, total catch by set, and catch by individual hook. Overall EM and observer catch estimates agreed within 2%, and individual identifications by hook agreed in over 90% of the catch records. EM reliably (i.e., accuracy within 10%) distinguished thirteen species that represented 97% of the halibut fishery catch. Some species, particularly non-distinct forms, were not identified well by EM. Sample sizes were too small among half the species for determination of an EM species identification capability. Close agreement between EM and observer was also evident with species utilization determination (i.e., kept or discarded) and time, location and depth at set start and finish.
The results of this study demonstrated that EM is a promising tool for at-sea monitoring applications. EM and observer programs differ in many ways in terms of data collection capabilities and program design issues. While the utility of this new technology will depend upon the specific fishery monitoring objectives, the substantially lower cost and broader fleet suitability of EM over observers makes this an attractive option. The authors suggest that a combined EM-based monitoring for the halibut fishery should be continued using two approaches: an integrated EM-observer program using both methods in a complimentary fashion to achieve fleet sampling objectives; and using EM and an electronic fishing log as an at-sea monitoring audit tool. Fruther testing using combined EM and observers on the same trip should occur in the ZN fishery to improve EM rockfish identification capability. The authors also recommend that DFO more comprehensively define the at-sea monitoring objectives of the halibut fishery and strengthen their support for EM-based monitoring approaches to further the development of this technology.

Studies of Patagonian toothfish size composition in fishing area 48.3 were made to determine size at maturity for male and female individuals.A considerable amount of original data indicated that male Patagonian toothfish attained maturity being of a smaller size than female individuals. Half the males became mature when 73-75 cm long, while females matured when 94-96 cm long. Toothfish maturity ogive was drawn and compared with size composition in catches of recent years to show that currently long-line fishery has been taking large amounts of immature and newly matured fish

The main characteristics of Patagonian toothfish (Dissostichus eleginoides) catch dynamics off the South Georgia Island and Shag Rocks (sub-area 48.3) for the 1989-2003 period are given. Taken the intensity of fleet operation as an example in the sub-area, it was confirmed a decrease in catches both for 1000 hooks and vessel/day. The given objective long-term data evidenced a substantial decrease in catch per unit value and necessity of the more attentive approach to the assessment of the state of the toothfish population in this area of traditional fishing and more precautionary approach to the TAC.

The Age-Structured Production Model (ASPM) presented to previous meetings is refined to allow the estimation of a selectivity-at-age function that decreases at larger ages. This is, in particular, to accommodate the view of the August 2003 meeting of the Subgroup on assessment methods that 0.2 yr-1 is likely the largest value of natural mortality M that is plausible for toothfish. Catch, catch-at-length and GLM standardised CPUE data are all extended for one further year. Despite model refinements, the CPUE data and catch-at-length data remain sharply inconsistent within the modelling framework considered. The former suggests the resource to be heavily depleted, whereas the latter suggests quite the reverse. Priority areas for further investigation to attempt to resolve this inconsistency are suggested. In the meantime, based upon a cautious interpretation of projections over the wide range of current stock status that can be argued from these analyses, it is suggested that annual catch levels should not exceed a few hundred tonnes.

This year the Subgroup on assessment methods (SAM) requested that WG-FSA consider whether a shorter CPUE time-series would be preferable for use in its annual assessments. (WG-FSA-03/40 2003, paragraph 2.27). This paper explores some of the consequences of shortening the dataset in the application of the usual assessment method. In addition we investigate the incorporation of uncertainty in the standardised CPUE series into the method of Kirkwood and Constable (2000) via Monte Carlo simulations of the CPUE series. Truncation of the standardised series from WG-FSA 2002 results in only slight modification to the median escapement but will generally diminish the probability of depletion as the dataset is truncated towards the more recent years. The use of the standardised series from the GLMM of Candy (2003) shows a more pronounced consequence of reducing the time series, such that the escapement level increases while the depletion probability decreases as the time series is reduced to recent years. In contrast, the explicit incorporation of uncertainties in the CPUE series in the overall assessment shows that truncation of the CPUE series could have a much greater effect on the final assessment, depending on the model used. These results indicate that the procedure for incorporating CPUE into the assessment process needs to be generally evaluated as to the consequences of its use in providing assessments that will meet the objectives of CCAMLR.

Operational interactions between marine mammals and the Patagonian toothfish (Dissostichus eleginoides) fishery were assessed in southern Chile through 7 surveys with observers on board industrial vessels between April 2002 and March 2003. Sperm whales (Physeter macrocephalus) occurred in higher frequency than any other species during fishing operations. In 60% of all monitored sets sperm whales were present, while orcas (Orcinus orca) were found in only 10% of these. When cetaceans were present, evidence of damaged catch included lips, heads and trunks and a total of 121 lips, 16 heads and 3 trunks were recovered. Mean rate of predation was 3% (± 2% CI 95%; n=180 sets) and ranged between 0% and 100%. Considering that in 153 (84%) of the effectively monitored sets no interaction whatsoever was recorded and that the mode and median of the predation rate was 0, the global impact of cetaceans over the fishing yield is considered to be low. When mixed sightings of orcas and sperm whales were encountered (n=12) the rate of predation decreased to 0%. Upon detecting orca presence, sperm whales modified their surface behaviour, grouping into tight parallel formations. This suggests that orcas prefer attacking aggregated sperm whales instead of the line. High sperm whale densities were found associated to different hotspots which had high fishing yields. This relationship tends to support the hypothesis that the richest fishing grounds are also traditional feeding grounds for sperm whales. Monetary loss associated with operational interactions associated with predation reach USD$92,684 (C.I. 95% USD$47.302 - $153.745) for the whole fleet, with a mean loss per set of USD$138 (C.I. 95% USD$74,76 - 249,3).