CCAMLR

Upward-looking acoustic Doppler current profilers (300 kHz, ADCP) and echosounders (125 kHz) were deployed on moorings on- and off-shelf to the northwest of South Georgia to measure abundance of Antarctic krill continuously between 14 October 2002 and 29 December 2005. A distinct seasonal pattern in krill abundance was detected that recurred consistently over all 3 years. Krill densities in winter were predominantly low (mean = 18.7 g m-2 SD 24.3) but rose substantially by summer in each year (mean = 89.5 g m-2 SD 64.2). A simple polynomial regression model with time as the independent variable explained 71% of the observed week-week variation. Mooring estimates of krill abundance were not statistically different (P>0.05) from estimates derived from standard ship-based krill surveys in adjacent periods suggesting that the mooring point estimates had relevance in a wider spatial context (ship surveys cover c. 100 x 100 km). Mooring data were used to explore whether high frequency temporal variation (i.e. within-year) could have led to the perceived between-year variation from previous summer surveys in the South Georgian western core box region between 1990 and 2005. Comparison of these ‘snap-shot’ ship survey estimates with the observed pattern of within-year variability showed that some of the alleged ‘year-to-year’ variation could be attributed just to sampling at different dates of year. However, there were some survey estimates that were significantly different (P

Antarctic krill has been studied for many decades, but we are still long way from understanding their biology to be able to make reliable predictions about the reaction of their populations to environmental change. This is partly due to certain difficulties in relation to logistics, operations and survey design associated with scientific surveys that have been obstacles for us to better understand krill biology. The krill fishery is the largest fishery in the Southern Ocean, continuously operating since early 1970s. Recent studies revealed its potential to be used as a unique source for scientific discussions to understand krill biology. In this paper, after a brief overview of krill fishery operation and krill biology, we examine how current data collection through the fishery operation could contribute to a greater understanding of krill biology, and then suggest future priorities for fisheries-related research in relation to recent changes in the Southern Ocean environment.

A long term study on the maturity cycle of Antarctic krill was conducted in a research aquarium. Antarctic krill were either kept individually or in a batch for 8 months under different temperature and food conditions, and the succession of female maturity stages and intermoult periods were observed. In all cases regression and re-maturation of external sexual characteristics were observed, but there were differences in length of the cycle and intermoult periods between the experimental conditions. Based on these results, and information available from previous studies, we suggest a conceptual model describing seasonal cycle of krill physiology which provides a framework for future studies and highlight the importance of its link to the timings of the environmental conditions.

We have substantially revised the krill-predator-fishery model that was presented to the WG-EMM in 2005. The new version of our model is called KPFM2, and we have addressed all four of the changes which the WG-EMM indicated would be required to use the model for providing advice on the allocation of catch among the SSMUs (i.e., add seasonality, consider alternative movement hypotheses, add thresholds in krill density that cause fishing to cease, and compute a performance measure that compares the distribution of simulated catch to the distribution of historical catch). We have added a substantial number of other features to the model as well. Many of these features were suggested to us at the 2005 meeting of the WG-EMM but not recorded as requirements; we have made a serious attempt to address most suggestions. These additional, features include
• predators that can forage outside their natal SSMUs;
• predators whose survival is a function of their foraging performance;
• differential competitive strengths among predators and the fishery;
• control over the seasonal timing of fishing and predator breeding that allows fishing and breeding to overlap or be disjunct;
• a facility for conducting simplified management strategy evaluations; and
• general improvements to the flexibility, performance, and usability of the model.
In our opinion, KPFM2 can be a useful tool for evaluating the outcomes of the six management procedures that are candidates for allocating the precautionary krill catch among SSMUs.

Responses of predator populations to environmental variability in the Antarctic have tended to exhibit site- and species-specific differences owing to variation in geographic settings and predator life-history strategies. Five populations of Pygoscelis penguins from King George Island and Livingston Island, South Shetland Islands, Antarctica, were examined to compare up to 25 years of data on the responses of sympatric congeners to recent changes in their Antarctic ecosystem. We used simple linear regression and correlation analyses to detect and compare trends in indices of population abundance, recruitment, and summer breeding performance of the Adélie (P. adeliae), gentoo (P. papua), and chinstrap penguins (P. antarctica). In general, the different trends in abundance and recruitment indices for each species, despite generally similar indices of summer performance, point to life-history-specific vulnerabilities during winter that contribute to differential survival rates of the penguins. In particular, significant relationships between indices of penguin and krill recruitment suggest that penguin populations in the South Shetland Islands may live under an increasingly krill-limited system that has disproportionate effects on the survival of juvenile birds.

We compare two versions of the krill-predator-fishery model to demonstrate the extent to which the predictions of KPFM1 can be reproduced with KPFM2. We also discuss the incorporation of seasonality into parameter estimates and a necessary change in the predator recruitment function of KPFM2. These comparisons provide a preliminary indication that the substantial changes in the structure and logic of KPFM2 have not caused substantial changes in model results. In essence, KPFM1 has become a special case of KPFM2. KPFM2 thus offers a flexible framework with functionality that the user can opt to use, should the user be able to provide defensible parameter estimates.

This paper addresses work conducted on the Mori-Butterworth multi-species model of the Antarctic ecosystem subsequent to the Ulsan meeting of the IWC Scientific Committee. Points raised about the model during that meeting are addressed in turn. Results are quoted that suggest that krill is indeed unable to fully utilise the primary production available. The precision of parameters estimated when fitting the model to abundance and trend data is reported. The model is extended to include an “other predators” variable (reflecting squid, fish and seabirds) so that the crabeater seal variable does not have to act as a surrogate for these in addition to the seals themselves. This results in an improved fit of the model to available abundance estimates for crabeater seals. A list of topics for possible further work on the model is presented. The development of an improved set of abundance and trend estimates for the various krill predators is seen as a priority for improving the reliability of current models, and it is suggested that this should be a key focus of the proposed joint IWC-CCAMLR workshop on this topic.

At the 2005 Scientific Committee (the Committee) Meeting (CCAMLR), Norway indicated that a Norwegian-flagged vessel, “Saga Sea” would be fishing for krill in the 2005/06 fishing season using modified gear and trawl system. The Committee agreed that this new technology would not be considered a ‘new and exploratory fishery’ if a monitoring system was implemented that provided adequate information on effort, catch characteristic and the broader ecosystem impacts of this new technology. In response to these concerns a monitoring system has been developed in collaboration between Norway’s Institute of Marine Research (IMR) and the UK’s Marine Resources Assessment Group and will be implemented onboard by a UK CCAMLR Scientific and National Observers.

Satellite telemetry was used to determine the winter movements and distributions of eight chinstrap penguins known to breed at one of two colonies in the South Shetland Islands, Antarctic Peninsula region during the 2000 and 2004 austral winters. Six birds from a breeding site in Admiralty Bay on King George Island (620 10’ S, 580 27’ W) were instrumented with satellite tags following their annual molt; similarly, two birds were tagged at their breeding site on Cape Shirreff, Livingston Island (620 28’ S, 600 46’ W). Chinstrap penguins were tracked successfully for one to six months following dispersal from their respective breeding colonies using the ARGOS satellite system. Data analyses revealed that 4 of the birds instrumented in the 2000 winter, two from each colony, foraged largely on the shelf to the north and northeast of the South Shetland Islands. Similarly, two birds tagged at Admiralty Bay in 2004 also dispersed to the Drakes Passage side of the South Shetland Islands. In contrast to the inshore locations utilized by all the penguins in 2000, both of the 2004 winter birds foraged well offshore, 350 to 500 km north of the Islands. Bathymetry and hydrological data, including SST and geostrophic velocities, suggest that the chinstrap penguins used markedly different winter foraging habitats in the 2000 and 2004 winters. The final two chinstrap penguins from Admiralty Bay, one from each winter, proceeded directly to the Elephant Island area and spent the next 2-5 months continually migrating eastward. Both of these penguins followed the Scotia Arc with the chinstrap penguin tagged in 2004 tracked to the vicinity of the South Orkney Islands where its signal was lost in April, a distance of 800 km from its breeding colony. The bird tagged in the 2000 winter continued towards the South Sandwich Islands until its signal was lost at 580 30’ S, 360 10’ W in late July, over 1300 km from its breeding colony. The migration path of both these birds was remarkably similar to the only other record of a chinstrap penguin’s winter migration reported by Wilson et al. (1998). Our results suggest that chinstrap penguins breeding in the same colonies during the summer have different migratory routes and winter habitats. The different migratory routes may reflect individual ties to different ancestral epicenters of chinstrap populations; one older and local in the South Shetland Islands and one relatively recent, arising from the emigration of chinstrap penguins that occurred during the expansion of this species in numbers and range in the middle of the past century.

A multidisciplinary, single-ship survey of CCAMLR Division 58.4.2 was conducted in January-March 2006, during which time multifrequency echosounder data were collected for the purposes of estimating the biomass (B₀) of Antarctic krill (Euphausia superba). The mean density of E. superba, integrated to 250 m depth across the survey area (1,566,157 km²), was 10.15 g m^-2. The total biomass was estimated to be 15.89 million tonnes with a CV of 47.93%. Most of the E. superba detected (80%) were in relatively weak aggregations (s_A <100 m² nmi^-2 for each 2 km-alongtrack integration interval), with 50% of integration intervals containing backscattering values <10 m² nmi^-2. Half of the biomass was found within 100 km of the 1000 m isobath, although aggregations often extended to the Northern ends of the transects at 62°S. The majority of acoustic detections were in the top 100m of the water column, centred around 50 m depth.