CCAMLR

We the undersigned wish to bring to your attention a potentially grave situation that needs to be addressed without significant delay. Together we have worked in the Ross Sea and vicinity for more than 300 person-years, and in the process have gained considerable knowledge about the Ross Sea ecosystem. Several recent findings indicate that the Antarctic toothfish (Dissostichus mawsoni) is rapidly disappearing from McMurdo Sound and vicinity, coincident with the maturation of the Ross Sea toothfish fishery from its initial experimental stage to its current near-quota status. Evidence is detailed in the EMM submitted document, “Decline of the Antarctic toothfish and its predators in McMurdo Sound and the southern Ross Sea, and recommendations for restoration.” We are concerned that this is the first sign that the Ross Sea ecosystem is being irreparably altered, and the 40-50 year time series of unequaled climate records and responses of the biota to climate change are in jeopardy of being compromised. The Ross Sea climate record heretofore had been free of confounding factors related to fishing and other, direct anthropogenic factors.

Analysis of the time series of the volume of water filtered during tows using a 1.8 m Isaac-Kidd Midwater Trawl (IKMT) from 1992 to 2007 showed a marked decline (~35%) in the volume of water filtered beginning in 2000. Analysis of tow time duration, reported ship speed during tows, and mean number of rotor counts from the flow meters showed no significant trends. The discrepancy in volume is traced to a simple arithmetic error in the calculation of the mouth area of the net. Since 2000, the net area was not calculated and instead only the length of the net was used in the determination of the flow constant. Thus, since 2000, the abundance of all zooplankton taxa have experienced a false increase in abundance. Representative corrected time series of Antarctic krill and three species of other Antarctic species is reported. The database has been corrected and protocols are in place to increase the quality control of data in order to ensure data integrity.

During February and March 2008 New Zealand carried out a major research voyage into the Ross Sea region in support of the International Polar Year Census of Antarctic Marine Life (IPY-CAML). The 50 day voyage on the research vessel Tangaroa involved an extensive survey of marine organisms from viruses to pelagic and demersal fish and cephalopods from the surface down to depths of 3500 m, and from the continental shelf and slope of the Ross Sea to unexplored seamounts and abyssal plains immediately to the north. Pelagic and benthic sampling gear, including plankton nets, mid-water and demersal trawls, seabed cameras, sleds, and corers were deployed in each habitat to obtain samples for a broad range of research programmes led by scientists from several New Zealand research institutes and universities with collaborating scientists from the USA and Italy. Despite some of the worst ice conditions for 30 years, a total of 282 gear deployments were made at 39 sites covering a wide range of habitats. Almost 120 fish and cephalopod species were collected and nearly 4,000 benthic invertebrate sample lots were brought back for identification and further study. A total of 55 hours of seabed video and 12,500 still images were also taken using a deep towed imaging system (DTIS). The results of the survey will be directly relevant to many aspects of the work of CCAMLR and its Working Groups. An important aspect of the survey was to collect data on key species or species groups such as mesopelagic fish that will provide quantitative inputs to the Ross Sea ecosystem model. Physical and biological data collected during the survey will also contribute to work being carried out on the biodiversity and bioregionalisation in the Southern Ocean. The benthic sampling using DTIS, sleds, and trawls has already improved our understanding of the distribution and abundance of benthic invertebrates (e.g., corals, sponges) found in vulnerable marine ecosystems in the Ross Sea region, and when combined with physical data should improve our ability to predict other areas where these species are likely to occur.

Despite much research on Euphausia superba, estimates of their total biomass and production are still very uncertain. Recently, circumpolar krill databases, combined with growth models and revisions in acoustics have made it possible to refine previous estimates. Net-based databases of density and length frequency (KRILLBASE) yield a summer distributional range of ~19 x106 km2 and a mean total abundance of 8x1014 postlarvae with biomass of 379 million tonnes (Mt). These values are based on a standardised net sampling methodology but they integrate over the period 1926-2004, during which krill abundance has fluctuated. To estimate krill biomass at the end of last century we combined the KRILLBASE map of relative krill density around Antarctica with the most recent, acoustics-derived, value for the CCAMLR Synoptic Survey of the Scotia Sea area (37.3 Mt). Thus the CCAMLR 2000 survey area contains 28% of the total stock, with total biomass of ~133 Mt in January-February 2000. Gross postlarval production is estimated conservatively at 342-536 Mt y-1, based on three independent methods. These are high values, within the upper range of recent estimates, but consistent with the concept of high energy throughput for a species of this size. The similarity between the three production estimates reflects a broad agreement between the three growth models used, plus the fact that, for a given population size, production is relatively insensitive to the size distribution of krill at the start of the growth season. These production values lie within the envelope of what can be supported from the Southern Ocean primary production system and what is required to support an estimated predator consumption of 128-470 Mt y-1. Given the current debate over acoustic methodology, plus the need for precautionary management of the developing krill fishery, our net-based data help to set a conservative estimate of total krill biomass.

1. We used the CCAMLR 2000 synoptic survey acoustic dataset to compare pelagic and shelf SSMUs in terms of the frequency of 1nm integration units with krill densities above and below a range of threshold values. 2. In general pelagic SSMUs had markedly lower frequencies of fishable integration units where the threshold density for fishing was set at 100 gm2 following Kasatkina (2003). 3. This was also true with other threshold values in the range 25 to 200 gm2 although the difference was smaller for higher thresholds. 4. The contrasting probability of encountering fishable concentrations in pelagic and shelf SSMUs suggests that the fishery will be less efficient and, perhaps, less economically viable in pelagic SSMUs. This is despite the fact that the absolute abundance of both krill and fishable concentrations of krill is higher in pelagic than in shelf SSMUs. 5. We also derived empirical relationships between SSMU-scale krill density and the frequency of fishable integration units for the full range of threshold levels. These relationships will be useful for linking the scale represented in operating models with those that affect the behaviour and performance of the fishery.

The “CCAMLR-IWC Workshop to review input data for Antarctic marine ecosystem models” will be held at the CCAMLR Headquarters in Hobart Australia on 11-15 August 2008. This paper provides an update on progress towards the holding of this workshop at the CCAMLR Secretariat . A revised budget is presented for consideration primarily to take account of the review materials being produced without expenditure from the budget, the re-costing of hosting the workshop by the CCAMLR Secretariat and the possible cost of publication. This has enabled the funding of more experts to attend the workshop. Coordinators have been appointed for all the data groups with the exception of the flying birds group, the work for which is being discussed with scientists involved in ACAP. An additional expert group has been added early in 2008 to review the state of the datasets on the exploitation of Southern Ocean species, including seals, whales, finfish and krill. A metadatabase has been established. The groups of experts have been assembled and work has been progressing within the individual groups. It is expected that all groups will have papers ready for consideration at the workshop, except for flying birds. The JSG agreed that the synthesis work will occur at the workshop rather than being attempted prior to the workshop. The workshop is open to members of the SC-CAMLR and SC-IWC and their working groups. Many relevant experts have been invited to attend with funding limited to one expert from each group, some experts that cover a number of groups and a group of experts familiar with statistics, assessments and ecosystem modelling. Originally, the outcomes of the Workshop were envisaged to comprise a paper from each of the expert groups, the metadatabase and a short report summarising the workshop and outcomes. When the material is outlined as a complete set the contents reveals itself to be a potentially exciting volume in parts and in total. It is apparent that such a volume could have appeal as book that could be incorporated into library collections by scientists, universities and others interested in the Southern Ocean and the issues faced by the CCAMLR and IWC. The paper describes how such a book might be organised. It also provides commentary on what might be included in the papers and a workshop report. In the case of the latter, it suggests that the workshop report be divided into a number of general categories on the different estimation and modelling tasks. SC-CAMLR (through WG-EMM) and SC-IWC are asked to consider and comment on the progress being made by the expert groups, the issues considered in the paper by the JSG and surrounding publication of the outcomes and whether a book would be a suitable outcome from this work.