CCAMLR

The ability to use upper-trophic level species as ecosystem indicators is determined by the ability to relate changes in indices of their performance to changes at lower trophic levels. Using indices of predator performance from four species of krill-eating predator together with independent ship-based acoustic estimates of krill abundance from South Georgia the relationship between a range of indices of predator performance and krill abundance was examined. There was a distinct relationships between the variability of indices and the biological processes that they measured; body mass parameters had the lowest variability (CV 50 %. Predator parameters that reflected processes occurring during the summer showed the closest relationship with krill abundance, especially those for species with foraging ranges similar to spatial scales at which krill surveys were undertaken. Population size parameters showed no functional response relationship with annual krill abundance estimates. Combining the summer parameters into a single combined index provided a better fit with the krill data than any of the individual parameters.

Mackerel icefish have been harvested in the CCAMLR Region for over thirty years. In the Atlantic sector of the Southern Ocean they feed preferentially on krill and are themselves preyed upon by fur seals and several avian species. These attributes make them suitable for consideration within the CEMP. With that in mind the following indices are outlined that might be incorporated in the programme: Standing Stock, Cohort Strength and Recruitment, Natural Mortality, Length at Age 1+ and 2+ years, Condition, Gonad Maturity and Diet

Exchange of 61 wandering albatrosses Diomedea exulans has been recorded between the French Crozet Islands and the South African Prince Edward Islands, 1 068 km apart in the Southern Ocean. Most movements of banded birds (57) have been westwards, from the Crozets to the Prince Edwards. In all, 18 fledglings banded at Possession Island, Crozets, have bred at Marion Island, Prince Edwards, but only one fledgling from Marion Island has been recorded breeding on Possession. The wandering albatrosses of the two island groups form a metapopulation that ideally should be conserved as a single unit. Its is suggested that France and South Africa collaborate through the Agreement on the Conservation of Albatrosses and Petrels to effect an improved conservation status for the wandering albatrosses of the two island groups.

Krill length frequency distribution through subarea 48.3 in 1988 January-February is considered in the frame of hypothesis of krill resources forming from two sources: Antarctic Circumpolar Current and Weddell Scotia Sea water flow. It is shown, that small krill with the mode of about 33 mm is distributed in the coastal zone of about 7-40 miles wide, further is situated the boundary zone at the distance of about 30-60 miles, beyond boundary zone occurs larger krill with the mode of about 49 mm. Krill length frequency distribution is unimodal in the coastal and off-shore zones and bimodal in boundary zone. Krill distribution well corresponds to the water flows mentioned. Further analyses revealed heterogeneity in Weddell Sea krill distribution, there are spots of krill of increased length, where krill is retained for certain time and have a possibility to grow longer. Difference in krill length in such spots and main water flow may reach 6 mm. Such spots may be considered as initial stage of krill aggregations forming inside quasi-stationary vortices, further development of this scenario leads to the creation of commercially important krill aggregations.

Heart rate (fH), abdominal temperature (Tab) and diving depth were measured in thirteen free-ranging breeding female macaroni penguins. Measurement of these variables allowed estimation of the mass-specific rate of oxygen consumption (VO2) while diving and investigation of the physiological adjustments that might facilitate the diving behaviour observed in this species. In common with other diving birds, macaroni penguins showed significant changes in fH associated with diving, and these variables accounted for 36% of the variation in dive duration. When VO2 was calculated for dives of different durations, 95.3% of dives measured were within the calculated aerobic dive limit (cADL) for this species. Mean fH for all complete dive cycles was 147±6 beats min–1. When this fH is used to estimate VO2 of 26.2±1.4 ml min–1 kg–1 then only 92.8% of dives measured were within the cADL. Significant changes in abdominal temperature were not detected within individual dives, though the time constant of the measuring device used may not have been low enough to record these changes if they were present. Abdominal temperature did decline consistently during bouts of repeated diving of all durations and the mean decrease in Tab during a diving bout was 2.32±0.2°C. There was a linear relationship between bout duration and the magnitude of this temperature drop. There was no commensurate increase in dive duration during dive bouts as Tab declined, suggesting that macaroni penguins are diving within their physiological limits and that factors other than Tab are important in determining the duration of dives and dive bouts. Lowered Tab will in turn facilitate lower metabolic rates during diving bouts, but it was not possible in the present study to determine the importance of this energy saving and whether it is occurs actively or passively.

The study examined the distribution of critical habitat for foraging by female Antarctic fur seals breeding at the island of South Georgia. Bathymetric features of the continental shelf around the island of South Georgia were an important indicator for the localisation of foraging. This pattern was consistent among years of different prey availability. Lactating females were constrained to forage mainly within 100 km of the location at which the offspring was being raised. When this constraint was removed at the end of lactation, females foraged to much greater ranges and dispersed to specific regions of the continental shelf east of Patagonia (>1000 km) and to the northern edge of the Antarctic pack ice (500 km). The empirical distribution of foraging during the breeding season was used to develop a function that described the foraging distribution for the whole breeding population of females. The result was consistent with past observations from ship-based surveys and it allowed estimation of the spatial impact of breeding female fur seals on krill at South Georgia. This suggested that, in extreme cases and assuming that krill influx is limited, female fur seals could eat most of the krill present in some regions where they forage intensively. However, mean consumption was about one-tenth of the mean density of krill.

Chinstrap penguins Pygoscelis antarctica are one of the major consumers of Antarctic krill Euphausia superba in the Southern Ocean. To examine their foraging strategy, we studied foraging trip patterns and diving behaviour of chinstrap penguins breeding at Signy Island, Antarctica, using time-depth recorders. Foraging trips of penguins could be divided into 2 groups, short diurnal (7.8 h) and longer overnight (19.9 h) trips, with diurnal trips (74%) being dominant in number (263 out of 355 trips). The diving depths of our study birds were much deeper (to 179 m) than previous studies on this species, with modal maximum dive depth at around 90 to 100 m. Diving patterns and profiles included typical pelagic dives, but also included series of consecutive square-wave shaped dives reaching similar maximum depth, the typical characteristics of benthic dives. These benthic-type dives were more abundant in diurnal foraging trips than overnight trips. Analysis of stomach contents showed that penguins on both types of trip fed almost exclusively on Antarctic krill. There was a positive relationship between indices of the proportion of benthic feeding and of foraging efficiency (stomach content mass divided by foraging trip duration). These results highlight the potential importance of benthic feeding on Antarctic krill, the first such recorded instance for chinstrap penguins. This previously undescribed foraging strategy by one of the major avian consumers of Antarctic krill provides a new insight into the predator-prey interactions of the Antarctic coastal marine ecosystem.

With the intent of stimulating discussion, we present four options for subdividing the precautionary catch limit of krill for Area 48 into the small-scale management units (SSMU) adopted at CCAMLR-XXI. The first three are static allocations: the first is proportional to estimated predator demand in each SSMU; the second is proportional to the estimated standing stock of krill in each SSMU; and the third is proportional to the standing stock less predator demand in each SSMU. The fourth option is a dynamic allocation based on land-based predator monitoring conducted just prior to or early in the fishing season.

The various CPUE indices used in Soviet krill fishery statistics and their main sources and primary data for their calculations were considered. The main CPUE indices were catch per fishing day (CFD), catch per extended fishing day (CEFD) and catch per hour (CH). The primary data for all the calculations were catch per haul and haul duration. There is rather high correlation between mean monthly values of CFD and CEFD, and CFD and CH. Instead, correlation between daily values is rather low, due to high fluctuations in hauls duration caused by fishery strategy directed to different final product of fishery: human consumption, krill meal and frozen krill. When considered separately for different strategies and so hauls duration, mean daily CFD and CH are well correlated. Depending on the strategy, number of hauls per day ranged from 1 to 15, mainly 2-4, hauls lasted from 0,1 to 16 hours, mainly 3-8 hours. The higher requirements for the final product quality, the shorter haul duration and so the higher number of hauls per day. The histograms of distribution of various CPUE, hauls duration, number of hauls per day and linear regression equations allowing mutual conversion of the CPUE indices are presented.

1. Changes in species’ abundance and distributions caused by human disturbances can have indirect effects on other species in a community. Although ecosystem approaches to management are becoming increasingly prevalent, they require a fuller understanding of how individual behaviour determines interactions within and between species.
2. Ecological interactions involving krill are of major importance to many species within the Antarctic. Despite extensive knowledge of the ecosystem that they occupy, there is still incomplete understanding of the links between species and the effect of environmental conditions on these interactions. In this study, we extended a behavioural model used previously to understand the interactions between penguins and krill to determine the indirect effect of krill fisheries on penguin foraging success and behaviour in adjacent breeding sites.
3. Increased fishing pressure offshore is predicted to reduce penguin food intake. Given the documented links between krill and penguins, this also leads to a prediction of decreased penguin survival and reproduction. Krill behaviour is predicted to cause stronger effects of krill fisheries than explained solely by the percentage of biomass removed. Environmental conditions that decrease krill growth rates or cause krill to spend time in deeper water are also predicted to increase the magnitude of the effect of fishing on penguin success. We show that changes in penguin foraging behaviour can be used to assess the impact of local fisheries on penguin reproductive success.
4. Synthesis and applications . These results demonstrate that an understanding of predator–prey interactions, indirect effects between species, and individual behaviour is imperative to our ability to manage populations. We describe a general method to use what is known about ecological and evolutionary processes with species-specific information to predict the response of organisms to novel situations. We further show how individual behaviour can be used to assess the impact of human disturbance on ecosystems.