CCAMLR

Although the IATTC does not have an established observer program in its longline fisheries, one does exist for a US-based pelagic longline fishery for tuna and swordfish. These vessels are subject to pertinent US regulations as well as under the purview of IATTC. In response to a CCAMLR query in 2002, IATTC informed CCAMLR of this US observer program. Information about seabird bycatch observed in the US West Coast pelagic longline fishery was reported by the US in WG-FSA-02/39. Per a standing request from CCAMLR for information on incidental seabird mortality in fisheries adjacent to the Convention Area, information is provided about the US West Coast pelagic longline fishery.
Pelagic longline vessels operating in the North Central-Eastern Pacific targeting broadbill swordfish (Xiphias gladius) and tuna (Thunnus spp.) inadvertently hook and kill black-footed (Phoebastria nigripes) and Laysan albatrosses (P. immutabilis) that nest in the Northwestern Hawaiian Islands. The US-based pelagic longline fishery does not interact with albatross or petrel species that breed in the CCAMLR Convention Area. Although procellarids demonstrate broad and far-ranging foraging distributions, it is doubtful that Southern Hemisphere albatrosses and petrels forage this far north.

The United States Antarctic Marine Living Resources (U.S. AMLR) program has conducted bottom trawl surveys of the South Shetland Islands (Subarea 48.1) during the 1998, 2001, and 2003 austral summers. Information on species and size composition, abundance, spatial distribution, and dietary patterns from the 2003 survey is presented. The spatial distributions and standardized densities for demersal finfish species have remained relatively consistent across all surveys. Shelf regions of importance for krill, fish, and benthic feeding guilds based on stomach content analysis demonstrate the most important feeding areas lie to the west and north of Elephant Island and to the north of King George Island greater than 200 meters. Estimates of total stock biomass from these surveys were computed for eight species: Champsocephalus gunnari, Chaenocephalus aceratus, Chionodraco rastrospinosus, Gobionotothen gibberifrons, Lepidonotothen larseni, Lepidonotothen squamifrons, Notothenia coriiceps, and Notothenia rossii. The standing stock for most species has fluctuated, with no signal of substantial year classes or significant recruitment for any species. Although standing stocks of G. gibberifrons remain the largest relative to all other species, there appears to be a decline in biomass. The overall abundance of finfish in the South Shetland Islands has yet to reach a level at which commercial exploitation would be advisable.

The Atlantic Yellow-nosed Albatross (Thalassarche chlororhynchos) breeds only at the Tristan da Cunha archipelago and Gough Island in the central South Atlantic Ocean, and is threatened by mortality from longline fisheries operating in the South Atlantic. Demographic data have been collected from two study colonies on Gough Island and Tristan da Cunha for 20 years. Annual variation in the number of breeding birds was strongly correlated between the two islands, and over the whole study period both study populations have trended downward at around 1.2% per year. The number of established breeders on Gough Island has declined more rapidly, and significantly, at an annual rate of 2.3%. Monitoring established breeders maybe a sensitive means of detecting population trends. Average breeding success (67–69%) and breeding frequency (66–65%) were very similar on the two islands. On Gough Island immature and adult annual apparent survival averaged 88 ± 3% and 92 ± 1%, respectively, and apparent survival from fledging to age 5 has averaged 31 ± 8%. Apparent adult survival on Tristan da Cunha averaged only 84 ± 2%. Annual survival of Tristan birds was negatively correlated with longline fishing effort in the South Atlantic Ocean. Population modeling predicts annual rates of decrease of 1.5–2.8% on Gough Island and 5.5% on Tristan da Cunha. Comparison with congeners suggests that the observed and predicted decreases are most likely to be caused by low adult and immature survival. The conservation status of Atlantic Yellow-nosed Albatrosses should be changed from Near Threatened to Endangered.

Mortality in longline fisheries is a critical global threat to some seabird species. Identifying
andmainstreaming seabird avoidance methods that not only have the capacity to minimize bird interactions, but
are also practical and convenient, providing crew with incentives to employ them consistently and effectively,
will help resolve this global problem. Cooperative research and a commercial demonstration were conducted to
assess three methods’ effectiveness at avoiding incidental seabird capture, commercial viability, and practicality
in the Hawaii pelagic longline fisheries. A seabird avoidance method called side setting, which entails setting
gear from the side of the vessel, with other gear design the same as conventional approaches when setting from
the stern, had the lowest mean seabird contact and capture rates of treatments tested. Because side setting
promises to provide a large operational benefit for longline vessels, the incentive for broad industry uptake and
voluntary compliance is realistic. After making the initial conversion to side setting, there is no additional
effort required to employ the method. A seabird avoidance method called an underwater setting chute also
holds high promise, but requires additional research and evaluation to correct design problems, after which it
can be considered being made commercially available. Two chutes, one 9m long and one 6.5m long, which
deployed baited hooks 5.4m and 2.9m underwater, respectively, were used in this trial. The 9m chute had the
second lowest mean seabird interaction rates when used with swordfish gear, and the 6.5m chute had the second
lowest mean seabird interaction rates when used with tuna gear. A third seabird avoidance method, which
entails thawing and dying bait dark blue to attempt to reduce seabirds’ ability to see the baits by reducing the
bait’s contrast with the sea surface, was found to be less effective than the other two methods and was found to
be relatively impractical and inconvenient. If pre-dyed bait were commercially available, use of blue-dyed bait
in combination with other methods, such as side setting and adequate line weighting, has high promise.

A set of procedures for modelling catch and effort data using generalized linear mixed models (GLMMs) including data analytic methods for examining the appropriateness of model structure and parameter values was presented in WG-FSA-SAM 03-12 using Dissostichus eleginoides in Subarea 48.3 of the CAMLR area as an example dataset. The application of these procedures to trawl catches of Champsocephalus gunnari in Subarea 58.5.2 is described. For the trawl catch and effort data it was found the precision of the standardised CPUE estimates was considerably poorer than that of the longline data for Subarea 48.3. It is concluded that CPUE was relatively stable from the start of the fishery until 2000, after which time there was a sharp increase in 2001 with a steady decline thereafter. The sharp increase in 2001 is most likely the result of the large abundance of 3 and 4 year-old fish in that year, which has since diminished through a combination of

A set of procedures for modelling catch and effort data using generalized linear mixed models (GLMMs) including data analytic methods for examining the appropriateness of model structure and parameter values was presented in WG-FSA-SAM 03-12 using Dissostichus eleginoides in Subarea 48.3 of the CAMLR area as an example dataset. Further development of these procedures is presented in this report using trawl catches for Dissostichus eleginoides in Subarea 58.5.2. The extension described here deals with calculating an overall standardised CPUE series when the Subarea has been divided into sampling strata by incorporating ‘Stratum’ as a fixed effect term and the Stratum-by-Year interaction (S x Y) as a random effect term in the GLMM.
Statistical methods are presented for examining the validity of considering the S x Y term as random. A random S x Y term avoids the difficulty in calculating an overall standardised time series of CPUE estimates of weighting by the areal extent of each stratum which is necessary when the S x Y term is included in the GLMM as a fixed effect. Defining an areal extent of each stratum that is valid for use in calculating a weighted mean over all strata using the formula based on stratified random sampling is problematic given that hauls are not a spatially random sample within each stratum. Including the stratum term as fixed simply results in uniform scaling of the CPUE series as is the case with other additive fixed terms in the GLMM.
It was concluded that there was an increase in CPUE in the second year of the fishery with a sharp decline in the following year followed by a relatively stable series of CPUEs. It was also shown that the influence on the series of the random effects estimates for Stratum-by-Year is small.
For the trawl catch and effort data it was found that considering the S x Y term as random was valid. The precision of the standardised CPUE estimates was considerably poorer than that of the longline data for Subarea 48.3. A weak trend of decreasing CPUE values with entry into the winter months was detected using a cubic smoothing spline.

A preliminary assessment of yield of Patagonian Toothfish, Dissostichus eleginoides, for Heard Island Plateau (Division 58.5.2) was done, using the standard CCAMLR methods, based on the result of a randomly stratified trawl survey completed between 16 April and 10 May 2003. The 2003 estimate of abundance of recruits indicates a continuation of a period relatively low recruitment since 1999. A minor revision to the recruitment series resulted in a relatively small reduction in the preliminary estimate of sustainable long-term yield assessed using the standard method. The preliminary estimate for 2004 was 2,680 t. Initial tests of length at age assumptions indicated that using a specified length at age vector that did not include growth beyond 15 years had only small effects on projected long term yields. Further work is required to evaluate the implications of current uncertainty in the rate of growth beyond this age at 58.5.2. Preliminary examinations of the effect of refinements to the design of the annual survey indicated some variability in survey catchability between years and suggest that it may be appropriate to adjust estimates of cohort strength for catchability where possible. The 2003 season saw the operation of the first commercial long line vessel in 58.5.2. An initial comparison of the length distribution of the catches suggest that the two gears sample a similar range of sizes. This initial comparison was somewhat confounded by the depth of the grounds fished by the trawl and long-line operations. Very few large (>1200 mm) fish were observed in the long-line catch. Further structured work is planned in conjunction with the commercial operators for the 2004 season to provide data for a more comprehensive comparison, and to sample greater depths that fished by the long line operator in the 2003 season.

A preliminary assessment of yield of Champsocephalus gunnari for Heard Island Plateau (Division 58.5.2) was undertaken using the standard CCAMLR methods, based on the result of a randomly stratified trawl survey completed between 16 April and 10 May 2003. The 2003 estimate of abundance was approximately 20% of the 2002 estimate. This decline in abundance is consistent with the passage of the strong 1997 cohort through the population and relatively weak recruitment in 1999 and 2000. The 1+ fish evident in the survey were not fully sampled and as such are not included in the assessment. Estimates of the strength of this cohort will not be possible until the May 2004 survey is complete. The estimates of short-term yield for 2004 and 2005 using the Mathcad implementation were 259 tonnes and 196 tonnes, respectively. Consideration is given to the potential use of alternative technical measures to control harvest of un-assessed cohorts and provide for more stable catches between fishing years, while meeting the objectives of Article II. Comparison of yield estimates between Mathcad and Generalised Yield Model (GYM) implementations indicated that the GYM version provided slightly higher estimates of short-term yield. These differences will need to be considered by the working group. The implications of the interannual variability in recruitment, natural mortality and growth of these fish, combined with the need to maintain a steady yield if possible need to be explored further in the development of a management procedure that fulfills the objectives of Article II and is robust against the uncertainties inherent in the stock dynamics of this species.

This note describes the activities of an alliance of New Zealand government, fishing industry and environmental groups that has formed to promote fishing practices that avoid seabird capture by fishing fleets in the southern hemisphere.

Following a finding that a small sample of aged Dissostichus mawsoni from McMurdo Sound (76° S) fell consistently below the von Bertalanffy curves calculated predominantly from data collected between 67 and 74° S, an investigation to test for latitudinal differences in growth rates was conducted. Length-at-age of Dissostichus mawsoni was compared across five zones in a 15.5° latitudinal range (62.5°–78.0° S). Between-zone comparisons were confounded by marked differences in the age structure of catches from the northern and southern sections of the range, and by the relatively high level of variance in the length-at-age data. There is no statistically significant difference in mean growth rates of D. mawsoni between 62.5° and 75° S. However, fish between the ages of 6 and 15 years in the southernmost zone (75–78° S) are, on average, significantly smaller at age than those in the more northern zones. There were insufficient older fish in the southernmost zone to enable a comparison with other areas. Any real latitudinal differences in growth rates for relatively sedentary fish are likely to be blurred by migration between latitudes.