CCAMLR

Krill demography and recruitment are tracked through time using scientific net sampling and predator diet sampling. Comparisons of these two methods show broadly coherent results but also frequently show differences that have fueled speculation of prey selectivity by predators. Krill, however, are not homogenously distributed and matching temporal-spatial scales of sample collections can be problematic. In this paper we use ARGOS satellite location data from foraging female fur seals to first identify foraging habitat and its proximity to breeding colonies where diet studies are conducted. We compare krill length frequency data collected over the entire West area of the U.S. AMLR survey grid with that collected only in fur seal foraging habitat. Both are compared to krill in fur seal diet. When spatial temporal scales for the two data sets are approximated as close as possible we found no difference in krill length frequency distributions. We suggest that fur seals are not selecting large krill while foraging but are instead selecting foraging locations that have larger krill in densities that maximize energy gain.

Preservation of ecosystem structure is the guiding principle by which the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) endeavors to manage the harvests of living resources of the Southern Ocean (with the notable exception of marine mammals). The experiences of CCAMLR with regard to fisheries on Antarctic krill (Euphausia superba), mackerel icefish (Champhsocephalus gunnari) and Patagonian toothfish (Dissostichus eleginoides) are reviewed. The unifying paradigm employed by CCAMLR is the application of a precautionary approach, which explicitly incorporates uncertainty in the analysis of risk of exceeding defined management criteria. Each fishery, however, presents a unique set of circumstances and unresolved concerns. While the current fishery for krill is small compared to the precautionary limit established by CCAMLR, fishing effort concentrated near colonies of land-breeding krill predators may pose a threat as well as those posed by the broader-scale influence of climatic cycles and trends on krill production. Management of the fishery on mackerel icefish relies on frequent surveys and short-term population projections because of high variability in natural mortality and is further complicated by the dual role of icefish as both consumers of krill and alternative prey to krill predators. While CCAMLR management of the fishery on toothfish is based on longer-term projections and has demonstrated success in addressing incidental mortality of seabirds, large-scale misreporting of catches threatens to compromise the viability of the fishery. These concerns are discussed in the context of CCAMLR’s long-term goal of feedback management schemes, whereby conservation measures are adjusted in response to ecosystem monitoring.

The Japanese R/V Kaiyo Maru will survey to collect data simultaneously on ecological interaction f environment – Antarctic krill – whales in the Ross Sea and adjacent waters during December 2004 and February 2005. Transect lines along 180, 175E and 165E will be set to cover hot spots where suggest high concentrated krill and whales such as the Scot Seamounts Island, the Balleny Islands, the shelf off the Victoria Land and the Bay of Whale Bay. The 175E line, especially, will be surveyed in detail from the surface to near the sea bottom on physical, chemical and biological parameters.

An assessment of the environmental processes influencing variability in the recruitment and density of Antarctic krill (Euphausia superba DANA) is important as variability in krill stocks affects the Antarctic marine ecosystem as a whole. Naganobu et al. (1999) had assessed variability in krill recruitment and density with hypothesized environmental factors; strength of westerly winds (westerlies) determined from sea-level pressure differences across the Drake Passage, between Rio Gallegos, Argentina, and Base Esperanza, at the tip of the Antarctic Peninsula, sea ice cover and chlorophyll-a in the Antarctic Peninsula area during 1982-1998. They found significant correlations between krill recruitment and those factors. Fluctuations in the westerlies across the Drake Passage were referred to as the Drake Passage Oscillation Index (DPOI). In addition, we had extended time series of DPOI using historical data from May 1952 to May 2003 and tested spectra analysis of the DPOI. The spectrum peaks are 20, 35 and 55 months including the short cycles of 6 and 12 months.

We compared physical parameters (temperature, salinity, density and geostrophic current) in order to investigate differences of oceanographic structures in the same area and summer season between the 1981 FIBEX survey and 2000 CCAMLR survey in the Scotia Sea, Antarctica. As a result, the distribution range of the cold Antarctic Surface Water less than 0°C in the 1981 FIBEX survey is clearly larger than the 2000 CCAMLR survey. In other words, the differences of the both surveys suggested that the Antarctic Surface Water in the 2000 CCAMLR survey as a whole reduced to the south compared with the 1981 FIBEX survey.

We examined seasonal variation in CPUE (catch per volume of trawled water) and diurnal vertical migration of Antarctic krill (Euphausia superba) associated with the brightness categories of the day based upon the angles between the center of the sun and the celestial horizon on the Scotia Sea; South Shetland Islands (SS), South Orkney Islands (SO) and South Georgia (SG) areas, using Japanese fisheries data.
Average trawling depth usually showed a marked diurnal change during summer and winter in SS and SO, being deepest around at daytime and shallowest around at nighttime from summer to winter, but did not show such diurnal vertical migration during winter in SG, being deepest around at morning twilight and shallowest around at evening twilight. The range of trawling depth was narrower in the certain layers (usually upper layers except in winter in SG) during dusk and dawn, but was expanded during morning and afternoon in every season in every area. Diurnal changes in CPUE occurred, being largest around at daytime and smallest around at nighttime during autumn and winter in each area, but being smaller around at daytime during summer in SS and SO.
Daily average trawling depth tended to be shallower during summer and early autumn, and deepened gradually from autumn and attained the maximum depth in winter over the Scotia Sea. However, it shifted to shallower in early spring, when krill began to feed on phytoplankton. Vertical range of trawling depth was narrower during spring and early autumn, but greater during middle autumn and winter in each brightness category.

We report of affected Antarctic krill (Euphausia superba) observed during the observation onboard the F/V Chiyo Maru No.5, from 08/08/03 to 17/09/03 in South Georgia region.

Japan has deployed one scientific observer on a Japanese krill trawler, Chiyo Maru No. 5, from 4 August 2003 to 21 September 2003. The observation was essentially undertaken following the CCAMLR Scientific Observers Manual. Summary of the fishing efforts, processing, fish by-catches, biological measurements of krill, product types, vessel and marine mammal observations are described in the report. The trawler made remain trips the west and north areas of South Georgia Island during observation.

Antarctic krill, Euphausia superba, comprise the foundation of the food-web in the Southern Ocean and are the target of a large fishery. Recently, the total abundance of krill in the Scotia Sea was estimated from an international echosounder and net survey (CCAMLR 2000) to be 44.3 million tons (CV 11.4%). The new biomass estimate prompted the Antarctic Treaty's Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) to revise the precautionary catch level for krill in the area from 1.5 to 4 million tons (SC-CAMLR, 2000). These survey results are based on the total echo energy attributed to krill, scaled by the Greene et al. model of krill acoustical reflectivity or target strength (TS). Presented here is a re-analysis of the CCAMLR 2000 data incorporating recent improvements in the characterization of krill TS. Results indicate that the estimated krill biomass in the Scotia Sea may be as high as 192.4 Mt (CV=11.7%), or as low as 109.4 Mt (CV=10.4%), depending solely on the expected distribution of krill orientations. As the lower krill biomass estimate is nearly 2.5 times the previous estimate, the standard krill TS model should be updated and a revision of the precautionary catch level for krill in the Scotia Sea may be warranted.

Sound scattering and absorption measurements were made of Northern krill (Meganyctiphanes norvegica) over the acoustical bandwidth of 30 to 210 kHz and compared to similar scattering measurements made of Antarctic krill (Euphausia superba; Demer and Conti, 2003a). The measurements of total target strength (TTS) match the SDWBA model (Demer and Conti, 2003b) recently developed for Antarctic krill, indicating its validity for other euphausiids species with similar size and shape. However, the total target strengths (TTS) of crustaceans with markedly different shapes (i.e. Mysidacea, a mix of Praunus flexuosus and Neomysis integer; and Decapoda, Crangon crangon), are not well predicted by SDWBA derived with the generic krill shape and scaled to animal length (L). This implies that crustacean target strength (TS) cannot be estimated accurately by a linear function of log10 (L), irrespective of shape, and brings in to question the validity of the current TS relationship used for Antarctic krill because that relationship was derived from data measured from multiple crustaceans including mysids and decapods. TTS and TS are dependent upon both L and shape, and krill, mysids, and decapods have significantly different shapes and girth-to-length relationships. On the other hand, modeled TTS and TS spectra for gravid and non-gravid krill appear to have differing amplitudes, but similar shapes. Additionally, the measurements of absorption spectra from decapods indicate that the absorption cross section increases with the volume of the animal. Collectively, these results provide tools for improving the detection of krill and more accurate estimates of TS, both vital to acoustical surveys. Furthermore, because TTS measurements from both northern and Antarctic krill support the SDWBA model, there are now more opportunities to apply acoustical measurements of one species to the acoustical characterization of the other. Thus, additional measurements of TTS over a range of frequencies, sizes and maturity stages will further improve our ability to identify species acoustically, aid ecosystem studies and assessment and management of both commercially and ecologically important euphausiid species.