CCAMLR

The effects of flipper bands, implanted tags/gastric lavage and external instrument attachment on the performance of Adelie penguins were investigated over three seasons at Bechervaise Island, Mac. Robertson Land, Antarctica. The return rates of birds carrying bands and/or implanted electronic transponders were compared to investigate the contribution of bands to bird mortality and to determine rates of band and tag loss. There was a reduction in return rates of birds banded for more than one season, but no evidence of band or tag loss over a single winter. The attachment of satellite tracking devices during the incubation period or for several consecutive trips during chick rearing resulted in increased foraging trip durations and reduced breeding success. Attachment for a single foraging trip post-hatching caused no significant increase in foraging trip durations nor any detectable effect on water turnover rates. No reduction in fledging rates of chicks from nests of stomach lavaged birds was detected over two breeding seasons. The implications of these findings for the CCAMLR Ecosystem Monitoring Program are discussed.

Diving behaviour of Chinstrap penguins (Pygoscelis antarctica) was recorded continuously by time-depth recorders from two adults breeding chicks. Their diving behaviour could be split into bouts by using log frequency method. Organization of dive bouts does not differ within each individuals among days on which dives are recorded but differed between individuals, suggesting that ecological and physiological restrictions differed between the two individuals.

Indices of predator reproductive status are calculated for CEMP parameters such as penguin weight, penguin chick weight, foraging duration, chick diet, and fur seal pup growth rates (Methods A1 - A9, B1-B2 and C1-C2) using data held at the CCAMLR Data Centre. Preliminary statistical and graphical analyses of the trends shown by the indices are also presented.

The position of the sea ice edge around the Antarctic continent was digitised into MAPINFO GIS software from the Joint Ice Centre weekly charts of sea ice distribution. The digitised images were then used to calculate the distance of the ice edge from CEMP sites throughout the year. These data are used to construct several of the indices associated with CEMP Environmental Monitoring Method F2: sea ice.

The use of time-depth recorders has revolutionised knowledge of diving activity of marine animals to the point where very detailed studies of variation in diving behaviour and performance between individuals, seasons and years are possible. The degree to which the sampling interval selected effects detection of dives and statistics of diving behaviour is investigated, using data from Antarctic fur seals and southern elephant seals representative of the extremes of diving in pinnipeds.
For both species the proportion of surface intervals recognised incorrectly (i.e. real dives artificially concatenated) increased monotonically as sampling interval increased. Effects were especially marked for fur seals: an increase in interval from 5s to 15s resulted in 20% of dives being unrecognised, a 38% increase in mean maximum dive depth, a 29% increase in mean dive duration and a 12% increase in duration of surface interval. In elephant seals an increase in interval from l0s to l00s produced changes of 10%. 5%, 13% and 18% respectively. Choice of sampling interval can therefore create significant biases, especially for species with diving characteristics similar to fur seals; critical comparisons should be confined to data collected using similar sampling intervals.

1. We examine the spatial distributions of pelagic seabirds and. fur seals near South Georgia, and asked to what extent the distributions of these predators were influenced by the spatial distribution of their principal prey, Antarctic krill Euphausia superba Dana. One novel aspect of our analysis is an explicit consideration of the separation in space between swarms of krill and aggregations of predators that feed upon krill.
2. Our data were collected in February 1986, during a systematic shipboard survey of the waters surrounding Bird Island, South. Georgia. Predator abundance was estimated visually using strip transects, and krill abundance was simultaneously estimated using a hull-mounted echosounder.
3. We approached the difficult analytical problems associated with spatial distributions of organisms by using spatial autocorrelation and cross-correlation analysis, regression models with spatial terms, and randomization tests. The randomization tests involved repeated simulations of predator distributions, and subsequent estimation of spatial association between predators and prey.
4. Pelagic birds and seals were distributed in a strikingly non-random fashion at sea near South Georgia; their distributional patterns were strongly influenced by the distribution of krill swarms.
5. Differences between predators in their spatial distribution and in their response to krill swarms suggest interspecific differences in foraging strategies.

Published in Journal of Animal Ecology (1993) 62, 000-000

We studied the distributions, abundances and interactions of macaroni penguins Eudyptes chrysolophus, Antarctic fur seals Arctocephalus gazella, and their zooplankton prey, in particular Antarctic hill Euphausia superba, near Bird Island, South Georgia, South Atlantic Ocean, in February 1986. Simultaneous surveys of marine birds, Antarctic fur seals and Antarctic krill were conducted along a series of transects radiating from the breeding colonies of the vertebrate predators. We examined the relationships between the distributions of predators and their prey with respect to the abundance of krill in the water column and marine habitats near the colonies. Antarctic fur seals and macaroni penguins showed positive correlations with Antarctic krill density across a wide range of spatial scales. Because krill was abundant dose to the colony and predator densities decreased with distance due to geometry, distance from colony was a confounding variable. When the influences of distance and direction on predator abundance were factored out, we were able to demonstrate an additional influence of Antarctic krill abundance at measurement scales between 10 and 100 km for Antarctic fur seals and for macaroni penguins at the scale of 70 to 100 km. Water depth was an important correlate of Antarctic krill and Antarctic fur seal abundances but not of the abundance of macaroni penguins. 'We found no evidence that the fur seals or macaroni penguins were concentrating their foraging for krill in the vicinity of the shelf-break.

Growth of upper canine teeth of male Antarctic fur seals (Arctocephalus gazella) which died of natural causes at Bird Island. South Georgia, was quantified from measurements of annual layers in longitudinal sections of teeth. Mean age at death was 7∙69 ± 0∙07 years and this showed a small but significant increase through the period when samples were collected (l972/73–1988/89). There were significant correlations between morphometrics of teeth and those of seals, suggesting that tooth growth provided an indication of body growth, Tooth growth rate was lowest in seals which died early (age 4 years) and increased with age at death. Changes in the growth pattern of teeth suggested that fur seals which became sexually mature early also died early. Tooth growth layers deposited in each calendar year were compared with the expected layer depth based on a linear relationship between layer depth and age at which each layer was deposited. There was significant variation in the depth of tooth growth layers deposited in different years, suggesting that growth was greater in some years than others. No trends in cohort strengths were detected, but particularly poor years for growth were closely related to years in which reproductive performance was also observed to be low, Variations in growth from 1967/68 to 1987/88 were correlated significantly (P