CCAMLR

The Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR) is currently considering plausible models of the Southern Ocean ecosystem within the Working Group on Ecosystem Monitoring and Management (WG-EMM). This paper describes properties for two groups of marine mammals that may be included in future ecosystem models of the Southern Ocean: cetaceans and pack-ice breeding seals. Important ecological differences exist among and between these groups, which should be considered in the development such models.

The extent to which the assumptions underlying line transect sampling are satisfied in shipboard surveys of crabeater seals hauled-out on the Antarctic pack-ice is examined. Crabeater seals showed little movement in response to the approaching ship. Movement away from the ship by seals close to the ship’s track was partially responsible for a relative lack of sightings close to the transect-line, but otherwise had little effect on the sighting histogram. Minor deviations from the transect direction to avoid running over seals violated the assumption of uniform distribution of groups, and contributed to a relative lack of sightings, close to (

Variability in the Southern Ocean is often characterised by fluctuations in the distribution and abundance of a single dominant zooplankton species, Antarctic krill Euphausia superba. At South Georgia interannual variability in the krill-based marine ecosystem has historically been most frequently detected in the response of upper-trophic level predators. Analysis of the changes in the population size structure of krill in the diet of Antarctic fur seals Arctocephalus gazella, particularly associated with periods of low krill biomass, has shown that the population dynamics of krill is a major factor in driving the inter-annual variability in its abundance. The ability to sample krill in the diet of predators at temporal scales not available using conventional (i.e. ship based) sampling methods has provided the basis for a re-evaluation of the role of recruitment variability and high rates of growth and mortality in generating the high amplitude of variability in krill abundance at South Georgia. Furthermore the production of a consistent index of krill population size composition from the diet of predators at Bird Island over the past decade has provided evidence for a relationship between sea-surface temperature and the level of krill recruitment. Krill-dependent predators not only show distinct behavioural responses to changes in krill abundance but also provide critical dietary data with which to elucidate the mechanisms underlying those changes. Using predators as samplers of commercial prey species can provide information on the key life-history parameters of prey species that are fundamental to reducing uncertainty in fisheries management models.

We present an initial analysis of the fishing locations, fishing depth and length-frequency distribution of krill at South Georgia during the winter of 2002 and 2003 and compare these with the length-frequency distribution and frequency of occurrence of krill in the diet of Antarctic fur seals. There were significant differences in the mean size of krill taken by vessels/measured by observers that should be addressed prior to more detailed analysis, nevertheless there was considerable overlap in the size composition of krill in the fishery and the diet of Antarctic fur seals. During the period of the winter when there was a reduction in the frequency of occurrence of krill in the diet of seals the fishery appeared to operate at greater depth suggesting a possible depth change of krill during winter. It may be appropriate to review the number of krill measured by observers in order to ensure that other sufficient time can be allocated to other activities, especially the assessment of by-catch.

The current approach to providing advice on the status of the krill-centric ecosystem relies on the evaluation of statistical anomalies in the CEMP database. A new approach based on the ordination of variables according to functional groupings is suggested. This approach uses the methodology developed within WG EMM to produce composite standardised indices (CSIs) from matrices containing missing data to summarise the variability in CEMP parameters.

The methods and presentation of CEMP parameters A1, A5 and A7 where evaluated using simulated time-series data. The effects of sampling timing and intensity during five-day periods for measures of arrival and fledging mass suggested that situations where sampling is distributed unevenly around the peak arrival/fledging date may introduce substantial bias in CEMP parameters A1and A7. The description of foraging trip duration using the mean arising from a bimodal distribution of trip durations may provide a useful index of foraging performance, however, the use of the 90th percentile of the cumulative foraging effort may provide a more sensitive measure of changes arising from changes in foraging strategies of penguins.

The Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR) is currently considering plausible models of the Southern Ocean ecosystem within the Working Group on Ecosystem Monitoring and Management (WG-EMM). The icefish, Champsocephalus gunnari, is one of the key components in the subantarctic marine ecosystem in the Scotia Sea and northern Kerguelen Plateau areas, as well as supporting commercial fisheries. Data on the species’ distribution, biology, ecological interactions and susceptibility to environmental change are summarised for use in ecological modelling work.

The Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR) is currently considering plausible models of the Southern Ocean ecosystem within the Working Group on Ecosystem Monitoring and Management (WG-EMM). Epi- and mesopelagic fish are key components in the oceanic (deep water) marine ecosystem throughout the CCAMLR area. While not in most cases the object of commercial fisheries, these generally small (

1. This paper describes temporal changes in foraging range throughout the breeding season of Adélie penguins nesting at Béchervaise Island on the Mawson coast of Eastern Antarctica. A decade’s worth of satellite tracking data was loaded into geographical information systems (GIS) software to produce maps of where the penguins travel to feed during each of the incubation, guard, crèche and pre-moult stages of the breeding cycle.
2. Penguins ranged furthest north during incubation and made their shortest trips during the guard stage of chick rearing. An annually recurrent polyna was consistently used as access to the sea during incubation.
3. Kernel analyses showed that penguins foraged most intensively at the continental shelf break and over submarine canyons, particularly whilst feeding chicks. Birds foraging prior to their annual moult travelled hundreds of kilometres to both the west and east of their breeding sites.
4. Foraging ranges at the different stages of the breeding season are consistent with the changing requirements of adults and chicks. However, increases in range as the chick rearing period progresses are also consistent with prey depletion and intraspecific competition.
5. Projection of the foraging ranges demonstrated for the Mawson coast onto other Adélie penguin colonies in the Prydz Bay region indicates varying degrees of overlap depending on the stage of the breeding season and the distance between populations. Overlap in foraging ranges between neighbouring colonies is least likely when chicks are small due to shorter foraging trips at this time.

The development of a general estimator of abundance would facilitate a standardised approach to regional and circum-Antarctic surveys of land-based predators. Such a generalised estimator is outlined, and its applicability illustrated by adapting it to the specific problem of estimating the abundance of Adélie penguins at regional scales in Antarctica, given a range of logistical scenarios and related survey designs.