CCAMLR

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.

The average CPUE values, annual and calculated for the periods of 1977-1986 and 1986- 1991 are considered. It is assumed that these values adequately describe trends in krill density fluctuations. Rather high stability of the values investigated is revealed. It is proposed that krill density of 170-200 g/m2 may be considered as an average characteristic value for the area 48. It was revealed, that interannual CPUEs variability is lower for the area 48 as a whole, comparing subareas, most probable due to the certain krill transport between subareas.

Diet sampling of Adélie penguins (Pygoscelis adeliae) was carried out at two colonies, in the Ross Sea, Antarctica, to study the feeding ecology of this species for the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) Ecosystem Monitoring Program. The study took place at Edmonson Point CEMP site over five years, 1995-97, 1999, 2001 and was extended to Inexpressible Island in 2001. Mean diet composition varied from year to year and between the two locations in 2001. Meal size for chicks was found to be higher during the crèche than the guard period and males were found to return with a larger mean meal weight containing more krill than females. The overall composition of diet varied between locations: mean weight of food and krill content were generally higher at Edmonson Point. In the guard period, mean weight of food was lower at Inexpressible Island. Mean content of Euphausia superba was significantly higher at Inexpressible Island while more E. crystallorophias was found in stomach contents from Edmonson Point.

This document outlines plans by Australia to conduct an acoustic biomass survey for krill in CCAMLR Division 58.4.2 (the South West Indian Ocean Sector) in January-March 2006. The survey is intended to produce a new estimate of B0 for this Division so that a revised precautionary catch limit can be established by CCAMLR. The planned survey will utilise a standardised design as adopted in previous B0 surveys in the CCAMLR Area and will use a similar methodology for collecting an analysing the data to that used on the CCAMLR2000 survey. The survey will be conducted from a single ship and will consist of 15 parallel transects between 30° and 80°E. The survey design is presented to WG-EMM for their comment so that any suggestions can be incorporated into the final design which will be presented to the Working Group in 2005.

This list of publications is for information only; it comprises a set of BAS papers that have relevance to the work of WG-EMM, but which do not relate directly to the current agenda.
These papers were produced by two BAS core funded science programmes: Dynamics and Management of Ocean Ecosystems (Principal Investigator: Eugene Murphy; Project Leaders: Phil Trathan and Jon Watkins); and, Albatross (Principal Investigator: John Croxall).