CCAMLR

1. Paired trials were undertaken to compare toothfish catch rates and by-catch composition on Spanish system longlines with those on ‘trotlines’ fitted with cetacean exclusion devices (cachalotera nets). 2. CPUE (kg/1000 hooks and kg/set) was greater for trotlines than Spanish system lines when cetaceans were present. This difference increased with increasing abundance of cetaceans highlighting the potential of this gear to reduce cetacean depredation. 3. By-catch to catch ratio was greater by number for Spanish system lines when cetaceans were present during hauling. 4. A large percentage of skates caught on trotlines fitted with cachalotera nets were dead or suffered life-threatening injuries. Toothfish were also in much poorer condition to the extent that they were unsuitable for tagging and releasing. 5. Consequences of a move to trotlines would therefore lead to: i. Some positive benefits by reducing cetacean depredation. ii. Significant problems in understanding the meaning of CPUE for trotlines, and consequently in understanding CPUE trends unless there is an extended period of overlap between Spanish system, autoline and trotline use. iii. Potential increases in skate and toothfish injury, leading to problems with skate discard survivorship and achievement of tagging goals.

Age and growth of spiny icefish, Chaenodraco wilsoni, were investigated using counts of annual growth increments from sagittal otoliths. Samples were collected during research surveys by benthic trawl carried out off Joinville-D’Urville Islands (Antarctic Peninsula) in February-March 2006 and January 2007. A total of 218 specimens were selected for the study, consisting of 120 females and 98 males. The age of fish was estimated by counting annuli on transverse sections obtained by grinding and polishing whole otoliths embedded in epoxy resin in moulds. The precision of age estimates between readings was tested applying both the average percent error (APE) and the coefficient of variation (CV). The estimated age range was 1-5 for males and 1-4 for females of C. wilsoni. Applying the von Bertalanffy growth function to the age-length data, a growth curve was obtained for each sex. The estimated values of VB growth parameters L∞ and k were respectively 32.7 cm and 0.81 for females and 32.7 cm and 0.68 for males. Age at sexual maturity was estimated to be about 2 years for females and 2.5 years for males. Compared to other channichthyids, the spiny icefish exhibited a high growth rate until they reached sexual maturity and a considerable short life span. The fish population of C. wilsoni caught in the studied area consisted mainly of adult specimens between 1 and 3 years of age, with very few older fish.

Catch limits currently in place for macrourids in Subareas 88.1 and 88.2 are defined as being equal to 16% of the catch limit of Dissostichusspp. in these subareas. The 16% was based on the ratio of the by-catch limit for macrourids to the catch limit for Dissostichus spp. in Division 58.5.2 in 2002/03 (CCAMLR-XXI, para 11.53). The bycatch limit for macrourids in Division 58.5.2 had in turn been based on the extrapolation of catch rates from a trawl survey of M. carinatus on Banzare Bank. Two bottom trawl surveys (IPY_CAML and BioRoss) have recently been carried out by New Zealand on parts of the continental slope of the Ross Sea in SSRU 88.1H. Whitson’s grenadier (M. whitsoni) was the most abundant species caught during both surveys, with mean catch rates in some strata being considerably higher than those recorded for M. carinatus on Banzare Bank. Because the strata covered by the New Zealand surveys represented only 25% of the continental slope of the Ross Sea, the data could not be used to calculate a biomass estimate for the entire slope directly. Instead, indicative biomass estimates for the rest of the area were made by extrapolating the more recent IPY-CAML survey catch rates across the entire slope. The extrapolations were carried out in two ways: (i) assuming M. whitsonidensities were constant across the entire slope and (ii) assuming M. whitsonidensities were proportional to the commercial macrourid CPUE from the fishery. The uncertainty of the extrapolated biomass was estimated through a bootstrap procedure. Indicative estimates of M. whitsoni biomass for the Ross Sea slope ranged from 26 892 t (cv = 29%) to 41 823 t (cv = 28%) depending on assumptions. Applying estimates of gamma (γ) =0.01439 and 0.01814 gave indicative estimates of yield in range 386–602 t and 487–759 t respectively. These indicative yield estimates provide tentative support for the bycatch limit of 374 t currently in place for M. whitsoni on the Ross Sea slope (SSRUs 88.1H–L and 88.2A–B).

during February and March 2008 as part of the International Polar Year. The main aim of the survey was to carry out a Census of Antarctic Marine Life in this regionfocussing on sampling the pelagic and benthic habitats on the shelf, slope, abyss, and seamounts in the Ross Sea region (CCAMLR Subarea 88.1). The shelf and slope were stratified by depth and at least three random trawls completed in each stratum. The trawl survey of the shelf area focused mainly on icefishes, notothens, Antarctic silverfish, and glacial squid whilst the survey of the slope area was designed to target the macrourid M. whitsoni as it is the main speciestaken as bycatch in the toothfish fishery, and the most important prey item in the toothfish diet. Biomass estimates and catch rates by station are presented for the eight most abundant teleost species along with scaled length frequencies of those species.

An ongoing mark and recapture experiment for skates was commenced by New Zealand fishing vessels in the Ross Sea (CCAMLR Subareas 88.1 and 88.2) in 1999/2000. Based on preliminary results from this programme showing an unquantifiable degree of the survivorship of returned skates, the CCAMLR Scientific Committee gave approval in 2004 for licensed vessels to cut live skates from the line (while in the water) as an alternative to either retaining all aboard or discarding dead skates, as a skate mortality mitigation measure. Initial opinion when the skate tag and recapture programme was first implemented was that some form of in-water release would be the ideal to improve survival chances. Subsequently a number of problems have become evident with this method. The Working Group on Fish Stock Assessment (WG-FSA) noted in 2004, when recommending skate release as an option to the Scientific Committee, that it might be difficult to detect tagged rays skates if they are cut off at the sea surface rather than being brought on board. The WG-FSA recommended that should the tag identification rate be low, a relaxation of the requirement to cut all rajids from the line on specified vessels and/or for specified time periods be adopted. Consistent with this recommendation, commencing in the 2006/07 season, New Zealand fishing vessels were given permission by the New Zealand government as part of the national research plan, to trial an alternative technique. The new method (for simplicity in this paper called Method 2), required the crew to bring the skate aboard carefully, remove the hook and snood, take and record biological (and potentially other meristic data) from a sub-sample when possible, and release live skates in a timely fashion in a manner most likely to ensure survival. The advantages of this method have been the more effective scanning of the captured skate for existing tags, greater accuracy in the assessment of ideal candidates for live release, the capability to collect supporting meristic and biological data for release candidates, correct species and sex identification, and the ability to more accurately place tags on the skate body – improving the quality of skate tagging. Following favourable results aboard by New Zealand vessels using Method 2 during the 2006/07 season and following a discussion and recommendation from WG-FSA 2007 an amendment to CM 33-03 (2007) was made stating that: ‘Unless otherwise requested by scientific observers, vessels, where possible, should release skates and rays alive from the line by cutting snoods, and when practical, removing the hooks’. This paper documents the evolution of skate release methods both for tagging and for live release for New Zealand autoline vessels. It describes the current Method 2 systems in use for two New Zealand vessels. A brief analysis based on data collected from the skates treated in this manner during the 2007/08 fishery in the Ross Sea is included in the document to highlight the additional advantages in data collection possible using Method 2. This paper is intended to inform WG-FSA with additional information collected over the last two fishing seasons in preparation for the ‘Year of the Skate’ prior to a final decision on skate release protocols. A proposal is made for a comparative experiment using two tag types to inform a final decision on a standardised CCAMLR tag type for Rajid mark and recapture programmes carried out within CCAMLR Dissostichus spp. exploratory fisheries.

Ontogenetic, inter-annual and regional variations in diet were investigated in mackerel icefish, Champsocephalus gunnari, in three successive summer seasons around South Georgia. Stomachs from 2239 icefish (130-560 mm total length) were examined. A bootstrapping technique was used to calculate confidence intervals for an index of relative importance (% IRIDC) of prey categories. Diet varied significantly between years and age classes but there was little regional difference in diet. In general diet was dominated by krill, Euphausia superba and by the amphipod Themisto gaudichaudii. Smaller (younger) fish tended to prey on a higher proportion of T. gaudichaudii and small euphausids such as Thysanoessa sp. and took smaller quantities of E. superba. In a season of poor krill availability (summer of 2003-2004) the proportion of krill in the diet, stomach fullness and fish condition (indicated by length-weight relationships) were significantly lower than in the other summer seasons. The poor krill season was followed by a large reduction (> 80%) in the estimated annual biomass of C. gunnari the following year (2005). This may have been a result of mortality of age 2+ and 3+ fish, which were more krill dependent than 1+ fish. Younger fish appear to have survived, leading to an increase in the estimated population biomass in 2006.

In April 2008 the UK undertook a bottom trawl survey of CCAMLR Sub-Area 48.3 on the FV Sil, with 70 bottom trawls undertaken giving good geographic coverage. Using 10 strata and the updated sea-floor areas and adjusting this for the low headline height of the UK trawl (see CCAMLR WG-FSA (2003), the biomass of mackerel icefish was estimated to be 80,426 tonnes, with a lower 1-sided 95% CI of 30,050. Catch-weighted length frequencies indicated that icefish population was dominated by 2+ and 3+ fish, with differences in the size between Shag Rocks and South Georgia and with few small fish in the NW South Georgia area. A preliminary short-term projection of the mackerel icefish stock was run using standard CCAMLR parameters in the GYM. Two scenarios were tested, both assumed that all the 2007/08 catch that remained after the survey (1709 tonnnes) will be taken. Scenario 1, which included the 1+ fish produced yield of 3445 tonnes in Year 1 (2008/09) and 2318 tonnes in Year 2 (2009/10). In Scenario 2, in which the 1+ fish were excluded and biomass adjusted accordingly, yields were 3372 and 2248 tonnes in Years 1 & 2 respectively. The Patagonian toothfish population was dominated by the same cohort that has been detected by surveys since 2003, with no evidence of new recruitment since. Biomass estimates and length frequencies are reported for other non-target species. Conducing the survey in April was successful. The icefish appeared to be dispersed, which is amenable to a random trawl survey. There was evidence that the September 2007 survey under sampled the 2+ fish, meaning that September is not an ideal time for a survey.

Results of the survey of entanglements of Antarctic fur seals Arctocephalus gazella at Bird Island, South Georgia for the 18th consecutive winter (April to October 2007) and 20th consecutive summer (November 2007 to March 2008) are reported here. During the reporting period of 1 April 2007 to 31 March 2008 a total of 36 entangled seals were observed. Sixteen and 20 entanglements were observed in the winter and summer periods respectively. Entanglements classed as Severe or Very Severe accounted for 25% of winter and 10% of summer entanglements. During winter, synthetic string/longline material was the most commonly found item forming neck collars (44%), whereas during summer the largest proportion of entanglements were in sections of fishing net (40%). Packing bands were the second most abundant entangling material in both summer (38%) and winter (25%). The majority of entanglements (78%) involved juveniles (including pups and sub-adults), comprising 88% in winter and 65% in summer. Data for the winter period showed a decrease in the number of entanglements compared to the high levels during the previous season, but levels were still above the long term winter median (1990-2006). Data for the summer period showed a small rise in the number of entanglements compared with the previous season, but levels were slightly below the long term summer median (1989-2007).

This report details the twelfth annual survey of the incidence of entanglements of Antarctic fur seals Arctocephalus gazella and eighteenth beach survey of man-made debris at Signy Island, South Orkney Islands. Data are reported for the period 14 November 2007 to 13 March 2008. Three seals were observed with neck collars formed from fisheries related debris. Beach surveys recovered a total of 56 items weighing 11 kg, representing an increase from 2006/07 of 11% (by number) and 33% (by mass). There was a decrease in the number of plastic packaging bands with only two found in the current season (both of which had been cut open), marking a break in the otherwise continued rise in packaging bands observed. Styrofoam and other plastic waste was predominant, making up 64% of all items recorded. Fishing related debris contributed 11% of all items (9% rope and 2% trawl net webbing). These results show that the longevity of plastics and other materials with a high resistance to degradation in the marine environment remains a problem. The need for continued monitoring to ensure that vessels are aware of, and comply with, regulations prohibiting the disposal of debris at sea is paramount.

This report describes and quantifies occurrences of fishing gear, marine debris and hydrocarbons associated with seabirds at Bird Island, South Georgia for the period 1 April 2007 to 31 March 2008. It is the fifteenth such annual report. As in previous years, the majority of items (84%) of marine debris and fishing gear (mostly hooks and lines from longline fisheries) were found in association with wandering albatrosses Diomedea exulans, and very few in association with grey-headed Thalassarche chrysostoma and black-browed albatrosses T. melanophrys. Despite increased observer effort, a slight decrease was observed in the total number of items encountered (n=116) compared with the previous season. Two non-fatal entanglements involving a wandering albatross and a northern giant petrel Macronectes halli were observed, and in both cases the fishing gear was typical of that used in longline fisheries. There were no incidences of hydrocarbon soiling of seabirds during the reporting period.