CCAMLR

In 2001/2002 Russian and UK vessels undertook surveys for icefish at South Georgia. Both used acoustic and trawl methods, and this paper uses both datasets to explore the similarities and differences between the surveys and discuss how much of the variation between the vessels was due to differences in the gear used and how much was due to natural spatial/temporal variability of the stock.
The acoustic surveys indicated that icefish were not only located near to the seabed, but that a significant portion of icefish biomass was located in the water column. Thus the traditional approach of using bottom trawls to assess icefish standing stock has resulted in biased estimates below the true value: acoustic estimates are ~ 1.5 times greater This should be taken into account in the forthcoming stock assessment during WG-FSA–2002.
These results show that the current observation system for the collection of data for icefish stock assessment should be changed to include regular acoustic surveys. This will improve the stock estimates of this species, and to achieve this we recommend the development of new survey designs and corresponding manuals.

The total capture of rays in the Subarea 48.3 longline fishery is composed both of rays brought on board and a number that are knocked off the line or fall off before they reach the deck. We estimated total capture (ray numbers) for some of vessels fishing in Subarea 48.3 in 2001 by utilising new information collected by observers on the rays appearing during their tally period. This estimate is entirely independent of vessel records of landed and discarded rays. For the one vessel that we have good species composition and mean weight data we have extended the number estimate to give capture weight by species.

We describe a previously unknown Amblyraja, A..sp.anon, from South Georgia. In the past this form has been classified as Amblyraja. georgiana. A.sp.anon differs from A. georgiana in form, colour and patternation, maturity, male clasper length, and distribution. It is larger than A.georgiana, with females attaining total lengths up 122.5 cm and males 117.5cm, compared with 96 and 101 for A.georgiana. Male A. sp.anon attain 50% maturity at a total length of 97cm, 13 cm greater than the length at 50% maturity for A.georgiana. Comparisons of colour and patternation were found to be consistent within each form, but significantly different between forms. Male A.georgiana, were found to have proportionally longer claspers to total length (2.77% difference between averages) than male A.sp.anon. 94% of captures of A.sp.anon were found at depths >1000m, where 85% of A.georgiana were caught in depths between 300-500m. We conclude that A.sp.anon probably a separate species from A.georgiana. For the purposes of CCAMLR assessments and monitoring it should be treated as a s eparate species from A.georgiana.

The North Pacific Fishery Management Council (Council) recommended changes to the existing regulations for seabird avoidance measures required in the groundfish and halibut demersal longline fisheries off Alaska. One of the main recommendations is for the required use of paired streamer lines on larger vessels. Changes were based on research results from a two-year study conducted by the Washington Sea Grant Program (WSGP) on the effectiveness of seabird avoidance measures in the longline fisheries off Alaska. For complete details of the research, results, and recommendations, see the WSGP final report. The report, “Solutions to Seabird Bycatch in Alaska’s Demersal Longline Fisheries”, is available at http://www.wsg.washington.edu/pubs/seabirds/seabirdpaper.html and was submitted to CCAMLR in 2001 (WG-FSA 01/35). Rigorous experimental tests of seabird avoidance measures on the local abundance, attack rate, and hooking rate of seabirds in Alaska fisheries were conducted on vessels over 60 ft (18.3 m) LOA. Paired streamer lines of specified performance and material standards were found to successfully reduce seabird incidental take in all years, regions, and fleets (88 percent to 100 percent relative to controls with no deterrent). This proposed action is prompted for two reasons: 1) An industry request to the Council to strengthen the seabird avoidance measures, and 2) the availability of research results from a study on the effectiveness of seabird avoidance measures that suggest ways that the current seabird avoidance requirements can be improved.
The objective of the proposed regulatory change is to revise the current seabird avoidance requirements to improve their effectiveness at reducing the incidental take of endangered short-tailed albatrosses and other seabird species. The National Marine Fisheries Service (NMFS) is currently promulgating regulatory changes based on the Council’s recommendations.

In 2001, WG-FSA asked the Intersessional Subgroup on Sampling Catches from Longlines to develop recommendations on 1) subsampling methods using frames and sampling units based on time and gear; 2) the allocation of observer effort within longline haul and between hauls; and 3) the allocation of observer effort directed toward fishery target species versus ecological interactions. Both subsampling methods use the hauling completed within a day as a frame, and theoretically cover all fishing activity by sampling every day of hauling. Both methods essentially follow a multi-stage cluster sampling design, which could be implemented more rigorously if the CCAMLR objective was changed from sampling 60 fish/day, to sampling a set length of each line or number of hours of each day. The principal advantage of the time-based method is that it gives a frame that can be monitored easily using a watch, but the frame is based on the mean time that is taken for hauling which is itself a random variable. The gear-based approach uses a fixed frame, but monitoring the amount of line hauled can be difficult when sampling the target species. Sensitivity analyses used to examine present guidelines on sample sizes, indicated that increasing the number of fish sampled for length would not substantially increase the precision of the estimates for mean length. From the limited evidence available, seabird mortality rates are estimated sufficiently precisely at 25% coverage to be reasonably sure of detecting increases to unacceptable levels. Sampling toothfish for biometric data in the factory and observing the incoming line may usefully be allocated to different days, if done so randomly.

This report presents results from the first exchange of otoliths under the auspices of the CCAMLR Otolith Network (CON), following the Workshop on Estimating Age in Patagonian Toothfish held at the Centre for Quantitative Fisheries Ecology (CQFE), Old Dominion University, United States, from 23 to 27 July 2001. The National Institute of Water and Atmospheric Research, Nelson, New Zealand; Central Ageing Facility, Victoria Australia; and CQFE, each provided a sample of otoliths, processing and reading one randomly chosen otolith from each pair. Half of the remaining otoliths were sent to each of the other laboratories to process and read using their methodologies. Overall there was reasonable agreement in age estimations between all three readers, with no evidence of biases >2 years that would indicate major differences in the criteria used by the readers. Similarly, there was little evidence that the differences in preparation technique led to major biases or increases in variation in the ages estimated. Instead, there appears from these data to be a broad consensus on the otolith micro-features that need to be exposed during preparation, and the way to interpret them. Small biases and variance in several cases may be explained by apparent differences in the timing of formation of translucent zones between management areas, and readers’ interpretation of the first few translucent zones. Future CON exchanges should 1) define better how these differences in interpretation may affect age estimates, and 2) achieve consensus on their interpretation.

Framework for IPOA-Seabirds implementation and structure of NPOA-Seabirds is discussed. Interagency cooperation as well as international cooperation is vital for the efficient and effective implementation of IPOA and NPOA. Education and outreach activities are listed. Numerous opportunities for international outreach and cooperation occurred in 2002.

Estimates of age and growth were determined from 156 Macrourus carinatus otolith samples collected during two research voyages to Heard and McDonald Islands (Division 58.5.2) in 1992 and 1993. The estimated range of ages was 4 – 25 years. von Bertalanffy growth parameters were calculated for both sexes combined, resulting in values of: L8 = 635 mm, K = 0.088 and t0 = -1.8. The size at sexual maturity of M. carinatus was determined from 162 specimens collected during commercial fishing operations in the Heard Island region in 2000. The size at which 50% of the fish population is mature, L50 was 417 mm total length and the size at which 50% of the fish population have spawned for the first time, Lm50 was 512 mm total length. An updated length-weight relationship is provided from 633 specimens of M. carinatus collected from Heard and McDonald Islands and Macquarie Island. No difference was evident in the length-weight relationship from the two regions. Otolith and body size relationships were also calculated for M. carinatus from Division 58.5.2.

A survey of mackerel icefish, Champsocephalus gunnari, was undertaken in Division 58.5.2 in the vicinity of Heard Island in May 2002 to provide the information for an assessment of yield in the 2002/2003 CCAMLR season. This paper provides a preliminary assessment of yield using the assessment methods of CCAMLR and discusses the implications of these results in relation to previous CCAMLR assessments. The estimate of biomass of mackerel icefish for the population at Heard Island was not significantly different from previous years but the one-sided lower 95% confidence bound was greater than in 2001 probably because the population was more uniformly spread in the southeast with relatively high densities in that stratum. The composition of the population was observed to comprise a single large cohort of mostly three and four year old fish in May 2002. Given the size of the fish, the expectation from current estimates of length at age parameters would be for most of the fish to be three year olds. However, given the abundance of fish in the population and the age structure of fish last year, it would be more reasonable to conclude that most of the fish are four years old, as this age class comprised the larger fraction (93%) of the population last year. Two assessments were undertaken as a result of the potentially different interpretations as to the composition of the larger cohort. If the cohort comprised mostly three year old fish then the yield for 2002/03 is estimated to be 1990 tonnes. If it comprises mostly four year olds then the yield would be 1815 tonnes. It is also proposed that the minimum size of capture be increased for 2002/03 to protect the younger unassessed cohort of fish from being exploited as they potentially enter the fishery towards the end of the season.