CCAMLR

The exploratory fishery for Antarctic toothfish (D. mawsoni) has been operating for eleven years in Subarea 88.1 and for six years in Subarea 88.2. This report summarises the large amount of data collected on toothfish and the associated bycatch by all vessels participating in the fishery. All SSRUs in the two subareas except for 88.1D and 88.2C have now been fished. The 2008 D. mawsoni catch was the fourth highest on record with a total of 2666 t against a combined catch limit of 3207 t. The management of the SSRUs within the two subareas was changed for the 2006 season as part of a 3-year experiment (SC-CAMLR-XXIV). One of the aims of the experiment was to simplify the administration of the fishery by having fewer catch limits. This appeared to be moderately successful, with only one catch limit being slightly exceeded in the 2006 season, two catch limits in the 2007 season, and none in the 2008 season. The catch limit was under caught in both Subareas 88.1 and 88.2 during the 2008 season, primarily as a result of the ice conditions. The length frequency data from the Ross Sea fishery have been very consistent over the past 3–4 seasons. There is no evidence of any truncation of the overall length frequency distribution, and no evidence for a reduction in fish length in any SSRU over time. Although moderate numbers of small fish are caught in some years (e.g., on the Shelf in 1999 and 2001), these year classes are not seen in large numbers in later years in the fishery. So at this stage there is no evidence for strong variation in year class strength in the fishery.

A previous study on the age and growth of Amblyraja georgiana in the Ross Sea suggested that these skates initially grow very rapidly for about five years, after which growth almost ceases (Francis and Ó Maolagáin, 2005). We present an alternative interpretation of age and growth in A. georgiana that is radically different from the published interpretation. By counting fine growth bands in the caudal thorns instead of broad diffuse bands, we have generated growth curves that suggest much slower growth, greater ages at maturity (about 20 years compared with 6–11 years) and greater maximum ages (28–37 years compared with 14 years). Several pieces of circumstantial evidence support the new interpretation, but a validation study is required to determine which growth scenario is correct.

Photographs of skates taken by observers on New Zealand toothfish longliners in the Ross Sea were identified to species. Sample sizes were small, but indicated a ratio of 10.75:1 of Amblyraja georgiana to B. cf. eatonii, which is consistent with a previous estimate based on a large sample of tagged skates. Biological parameters were reviewed and updated for Amblyraja georgiana. Revised length-weight regression relationships for male and female A. georgiana confirmed that male and female relationships differ significantly. Better estimates of median length at maturity were made possible through a combination of improved observer staging of skates, and a moderate-sized sample of whole skates that was examined in the laboratory. There was no significant difference between the median length at maturity for male and female A. georgiana, which was estimated to be 67.3 cm pelvic length (= 96.5 cm total length). Nearly all of the skates caught were returned to the sea (discarded or tagged). A considerable proportion of these were returned in good condition and were considered likely to survive. Estimates of the proportion released in good condition are in the range 50–80%, depending on assumptions about whether skates were double counted, and whether all tagged skates were in good condition. Improved data recording using new fate and condition classes and a new data logsheet should provide better estimates of this parameter next year.

Conservation Measure 22-06, in the absence of site-specific or other conservation measures to prevent significant adverse impact on vulnerable marine ecosystems, requires specific actions to be taken when evidence of a Vulnerable Marine Ecosystem (VME) is encountered in the course of fishing operations. Monitoring fishing operations for encounters with evidence of a potential VME entails identification of specific taxonomic groups of invertebrates, such as sponges or corals. Identification of these organisms to the appropriate taxonomic grouping has not been a standard procedure, and no identification guide specific to both indicative VME taxa and Antarctic species has been developed. The objective of this guide is to provide observers on long-line vessels with a potential VME-taxa specific, quick, on-deck guide to aid in the classification of invertebrate bycatch into the appropriate groupings. The format of the guide is a “compare and contrast table”, using photographs and key characteristics to correctly classify likely VME taxa to the appropriate grouping. It also identifies those commonly mistaken for other taxa. It is printed as an A2 waterproof poster for display in the vessel factory or on deck for easy reference. Once classified, these observations can be used for monitoring evidence of a potential VME. Additional invertebrate identification guides are still needed for fine taxonomic resolution for all invertebrate bycatch.

The Ross Sea has been geologically characterized by tectonic and glacial processes. These processes have created diverse habitat, including distinct banks and basins. For many fish species the availability of habitat is critical to the long-term viability of the population. Antarctic toothfish (Dissostichus mawsoni) are subject to an increasingly important commercial fishery in the Ross Sea and yet little is known about habitat associations for different life history stages. To define and assess the availability of habitat for Antarctic toothfish a benthic habitat map of the Ross Sea was created based on the habitat mapping scheme developed by Greene et al. (1999). Fish age data from the long-line fishery in the Ross Sea were superimposed on the habitat map and broken into discrete spatial areas. Differences in age distributions between these areas were found using ANOVA. These distributions were consistent with an ontogenetic movement of fish from shallow continental shelf habitats to deep-water continental slope was documented. Younger, less mature fish were located on the continental shelf and older fish were located on the continental slope. In addition, the older and most mature individuals were found on ridges in the northern Ross Sea, consistent with the hypothesis of an austral summer spawning migration from continental slope to the ridge habitat of the North Ross Sea. An effective management strategy might focus on protecting the northern ridge habitat to maintain long-term viability of Antarctic toothfish populations.

Antarctic toothfish (Dissostichus mawsoni) are subject to an increasingly important commercial fishery in the Southern Ocean, yet many of their life history characteristics, including vital rates, remain unknown. In this study, Antarctic toothfish were aged using otolith age estimation criteria established for Patagonian toothfish, D. eleginoides, a closely related species. To validate estimated ages, the radioactive disequilibrium of lead-210 and radium-226 in otolith cores was measured and used as an independent chronometer to determine age. Age estimates indicated Antarctic toothfish live to at least 39 years of age. Estimated and radiometric ages were in close agreement, confirming age estimation criteria and an annual periodicity of otolith growth zones. Von Bertalanffy growth function parameters indicate Antarctic toothfish are relatively slow-growing (k = 0.111; t0 = -0.605), especially in relation to their maximum size (L∞ = 158.9 cm). These vital rates are discussed in the context of the growing Antarctic toothfish fishery.

The Uruguayan-flagged longliner Banzare experienced sea-ice related, operational difficulties in implementing the CCAMLR Tagging Protocol in Division 58.4.1 in 2007/08. Extensive sea-ice cover greatly increased the transit times between research haul locations, which resulted in long soak times and a high mortality rate of fish on these lines; only fish with a high chance of survival were tagged. In brief: • The vessel started fishing in Division 58.4.1 SSRU E on 6 January 2008 but only completed one haul (no catch) due to adverse ice conditions, and the vessel exited that Division; • The vessel returned to Division 58.4.1 SSRU C and resumed fishing on 27 January 2008, completing 16 hauls including 10 research hauls. The vessel then moved to SSRU E on 3 February 2008 and completed 3 hauls (note: SSRU G was closed on 30 January 2008). • The vessel caught a total of 9.757 t of Dissostichus mawsoni in Division 58.4.1 and tagged and released 10 fish (tagging rate: 1.02 fish/tonne), which was below the tagging rate of 3 fish tagged per tonne of green weight caught required in Conservation Measure 41-11(2007). The vessel and authorities were aware that the extensive sea-ice cover had prevented the vessel from tagging fish in Division 58.4.1 at the rate required by CCAMLR. As a result, the vessel made every effort to tag fish in excess of the required rate when the opportunity arose: • in Division 58.4.3a the vessel tagged fish at a rate of 4.9 fish/tonne; • in Division 58.4.3b the vessel tagged fish at a rate of 4.6 fish/tonne;

On the results of some field materials collected from 2002 till 2008, on the basis of length composition analysis of individuals, weight of females’ gonads and sex ratio an attempt was made to select locations and periods of Antarctic toothfish mass spawning in some areas of the Pacific Ocean and Indian Ocean sectors of the Antarctic. In the Ross Sea area the most probable areas are the Pacific Antarctic Ridge and the Amundsen Ridge in the Amundsen Sea area. In the Cooperation Sea area the most possible mass spawning place is the Banzare Bank. Obviously, the mass spawning is stretched and falls on the winter season, sometimes covering part of autumn or spring season.

Two species of deep-sea skates (Rajidae, Chondrichthyes) are newly recorded from the slope of the Crozet Archipelago. Specimens are preserved in collections, morpho-anatomical observations and molecular Barcoding are currently in process to identify that species.