CCAMLR

The ASPM assessment of the Prince Edward Islands toothfish resource by Brandão and Butterworth (2004) that permitted annual fluctuations about a deterministic stock-recruitment relationship is updated to take account of further catch, GLM standardised CPUE and catch-at- length information that has become available for the years 2004 and 2005. The assessment is also generalised to allow for a second fleet to accommodate data from a pot fishery that has been in operation since November 2004. Results obtained show a much greater selectivity for larger toothfish for the pot than for the longline fishery – a feature which has important implications for the status of the population. The possible extent of cetacean predation and its consequences are also investigated. Twenty year biomass projections under the assumption of various constant annual catches for the two-fleet model are computed. Although higher sustainable yields may be possible, it is suggested that a prudent management approach at this stage would be for the annual legal catch not to exceed 500 tonnes for the time being, together with encouragement that this be taken more by pots than by longline to reduce the impact of cetacean predation. Industry observations of the extent of cetacean predation for the longline fishery have proved helpful, and should be extended to a more formal data recording basis in the future.

One UK vessel fished around the South Sandwich Islands (Subarea 48.4) in in July, 2005 in accordance with CM 41-03. During this time fish were tagged in order to start a mark-recapture programme to assess the toothfish population. Catch rates were similar to those experienced in Subarea 48.3. The UK proposes to undertake a more extensive mark-recapture experiment in Subarea 48.4 over the 2006 – 2007 fishing seasons. The objective of the experiment will be to assess toothfish population structure and size. The research will be undertaken during April in each year by up to two vessels, details yet to be confirmed. The proposal is to tag 500+ fish taking 100 tonnes of catch each year. The target species will be D. eleginoides but any D. mawsoni caught will also be tagged or retained for analysis as appropriate.

The Patagonian toothfish longline fishery set approximately 7.5 million hooks and 9.6 million hooks in 2002/03 and 2003/04, respectively. Observers were present during the setting of 59% of all lines set during 2002 – 2004 to record adherence to the above provisions and record seabird mortality. Only Black-browed albatross (Thalassarche melanophris) mortalities were recorded. Estimated total mortality for 2002/03 was 80 Black-browed albatross and for 2003/04, 45 Black-browed albatross. The rates for 2002/03 & 2003/04 were 0.011 and 0.005 birds/1, 000 hooks, respectively, indicating that the toothfish longline vessels are meeting the requirements of the relevant National Plan of Action.

Information on Australia’s national albatross and petrel research programs is provided to CCAMLR as requested in IMAF Intersessional Workplan Item 2.1.

A description of the autoline fishing method, including standard terminology for the fishing operation and gear used is provided.

Results from the New Zealand research survey in CCAMLR Subarea 88.3 in February 2005 are presented. While ice conditions prevented the successful completion of the full research plan as approved at CCAMLR XXIII, research activities were completed with 10 research hauls, temperature profiling, icthyoplankton sampling, toothfish tagging and biological sampling of toothfish and other species completed.
Pre-recruit D. mawsoni were caught at much greater depths than occurs in the other Subareas of Area 88. This result has significant implications for future trawl surveys in this area. The catch rate obtained on one line on the Antarctic shelf is similar to catch rates taken in other Subareas and Divisions where substantial exploratory fisheries are currently under way. The limited results collected indicated a surprising lack of biodiversity in the De Gerlache Seamount study area.
While the results of this research survey are limited, they do suggest that further research activity is required in Subarea 88.3 before any fishing activity be permitted.

A number of morphological and reproductive measurements made seasonally on Antarctic toothfish Dissostichus mawsoni from mid-December to early April during the 2000-01 to 2004-05 fishing seasons aboard the autoliner San Aotea II have been analysed. Results of this study indicate measurable differences in a number of indices from toothfish found on the Ross shelf proper, as distinct from those sampled on the more isolated seamounts and features to the north. These are length modal distribution, sex ratio, fish body condition factor, and reproductive development. D. mawsoni samples from the northern part of the Ross Sea showed that this component of the population had a unimodal length distribution at a consistent peak over all sampling seasons in comparison with the southern group in which the distribution was multimodal, showed a consistent and significant higher ratio of males to females , was in poorer condition, and was more advanced in reproductive development.

Research undertaken in New Zealand on seabird interactions with fisheries, and research into the population status and distribution at sea of New Zealand seabirds is documented.

This report obtains estimates of observer coverage required to predict the total numbers of incidental seabird captures (albatross and petrel taxa combined) in a fishery with a specified coefficient of variation. Fisheries analysed are determined by the quality and the availability of data and a known history of seabird captures: the trawl fisheries targeting hoki in the Sub-Antarctic, on the Chatham Rise, and off the west coast of the South Island; the trawl fisheries targeting squid in the Auckland Islands part of SQU 6T and on the Stewart-Snares shelf; and the autoliner fisheries targeting ling on the Chatham Rise and in waters south of 46° S.
A random effects model was developed to enable the contribution from the correlation between the numbers of captures per tow/set by the same vessel to be included in the calculation of the coefficient of variation of the predicted total number of seabird captures. The model also permits the estimation of the contribution from the extra variation that arises from the tendency for seabird capture incidents to involve large numbers of birds on rare occasions. Estimates of the variance components were derived from models that were fitted using data from the 1999–00 to the 2002–03 fishing years for the trawl fisheries and from the 2000–01 to the 2002–03 fishing years for the longline fisheries.
The observer coverage fraction is expressed in terms of tows for the trawl fisheries and hooks hauled for the autoliner fisheries. The estimated observer coverage fraction required to attain a coefficient of variation of 30% in the fishery depends on the total effort and on the capture rate through the predicted total number of captures. The approximate coverage fractions required, based on typical estimated numbers of captures, were between 8 – 54% depending on the fishery and numbers of birds captured for trawl fisheries.For the ling autoliner fisheries, the required fraction of observer coverage does not depend to the same extent on the predicted total number of seabird captures because most uncertainty arises from between vessel variation. Through wide ranges of predicted captures the approximate effort coverage fractions required were between 70 - 91% of days depending on the fishery area.
Estimates of observer coverage required for both the trawl and ling autoliner fisheries can only be regarded as approximate since they are always based on variance estimates, which are notoriously uncertain. The ling autoliner fishery estimates however have an additional source of uncertainty that arises because there are few vessels involved in these fisheries and the distribution of the effort between the vessels can vary markedly between seasons. Thus, for the ling autoliner fisheries, the large values for the coverage required by days in the fishery combined with the large uncertainties in these estimates suggests that 100% coverage is desirable.

A review of the use and effectiveness of research lines as a data collection and effort spreading tool within the Ross Sea exploratory toothfish fishery (CCAMLR statistical Subareas 88.1 and 88.2) is presented. The increase in the number of vessels in the exploratory fishery in Subareas 88.1 and 88.2, combined with the greater number of Small Scale Research Units (SSRUs) and the amount of data collected through fishing activities has effectively made the requirement to force a spread of research sets (5 nm spatial separation) superfluous as other factors produce the same result. The paper also demonstrates that by-catch levels, particularly catches of Whitson’s grenadier (Macrourus whitsoni), are demonstrably higher on research hauls.
The paper concludes with a proposal for a more effective Research Plan for the Ross Sea exploratory toothfish fishery that achieves the requirement to collect biological, environmental, and longline specific data on both the target species and on other catch species in a non biased and statistically valid manner covering as wide a range as possible.