CCAMLR

First attempts were made in the early 1980’s to estimate the krill and pelagic food consumption by Antarctic demersal fish. These estimates were extended to the mesopelagic realm and the high-Antarctic Zone in the late 1980’s and early 1990’s when these areas were exploited commercially and a larger number of food studies were conducted. Currently, the best estimates of krill consumption by fish are 23 – 29 . 106 tonnes of krill and other pelagic prey taken annually by demersal fish and 7 – 44 . 106 tonnes taken by mesopelagic fish in the Atlantic Ocean sector only. However, these estimates still have wide confidence limits. Major shortcomings of the consumption estimated for mesopelagic fish are the validity of hydro-acoustic biomass estimates conducted in the late 1980’s and the lack of quantitative food consumption data in some abundant myctophid species. Major shortcomings of the consumption estimates of demersal fish are the inaccurracy of biomass estimates for some species, the shortness of most food studies which do not adequately grasp the opportunistic feeding habits of many demersal fish and the scarcity of quantitative winter food studies. However, it is evident from this review that the importance of krill in fish diets varies with time and location, and with the suite of prey types available in different regions in the Southern Ocean. Models of food web and ecosystem dynamics need to account for the role important taxa, such as myctophids, Champsocephalus gunnari, and other abundant channichthyids and nototheniids play as predators of krill and other pelagic resources. Furthermore, the effects of large changes in abundance and community structure of fishes brought about by industrial fishing needs to be considered.

This report reviews the availability of data describing penguin abundance in the CCAMLR Convention area, and the uncertainties in deriving overall abundance estimates from these counts. Counts of breeding colonies are available from a variety of sources and, when combined, coverage is thought to be reasonably comprehensive for some areas, but less complete for others. One key problem is that counts have been collected using various demographic units, and the timing of these have varied relative to availability of these units. Counts therefore have to be standardised prior to being summed, but the adjustment data required to achieve this are only available for a small number of site-year combinations. The other fundamental problem is that the latest site counts are of variable ages, and since penguin populations are known to vary with time the assumption of population stability since the most recent count cannot always be justified. Modelling approaches that may reduce these uncertainties are recommended and the errors and biases that are likely to arise from fitting these to penguin count data are discussed.

While the joint CCAMLR-IWC workshop will consider a number of parameters for species groups, including abundance, trends in abundance, habitat utilisation, foraging and growth, this review of pack-ice seals focuses primarily on abundance and to a lesser extent trends in abundance. The review addresses population surveys and abundance estimates for the four species of phocid seal commonly encountered in the pack-ice and fast-ice surrounding Antarctica (crabeater seal Lobodon carcinophaga, Ross seal Ommatophoca rossii, leopard seal Leptonyx hydrurga and Weddell seal Leptonychotes weddellii). The spatial scope covers the circumpolar extent of pack-ice, and the temporal scope spans a period of more than 50 years from when pack-ice seal surveys were first undertaken and reported in the 1950s to the present day. The review of abundance surveys is presented chronologically, and in doing so tries to provide a sense of evolution and development of methodologies over a 50 year period of application. The methodologies employed in individual survey efforts are described, and the likely biases and uncertainties in resulting abundance estimates are discussed. Abundance estimates from individual and collective survey efforts are provided. It is difficult to derive trends in abundance from these abundance estimates because there have been very few repeat surveys in the same or similar regions, methodologies have evolved and improved over time, and uncertainty around abundance estimates is substantial.

Ecosystem models are being developed to explore a range of issues globally. This paper is currently in draft form open to comment and is being developed to provide an introduction to the CCAMLR-IWC Workshop to review input data for Antarctic marine ecosystem models. It summarises background to the use of ecosystem models in CCAMLR and the IWC and a history of the developmental work in those organisations. It also provides an outline of the nature of modelling for these purposes and the general issues that need to be considered in parameterising a model, providing input data for those models and for addressing uncertainties in this process. Lastly, it summarises the modelling platforms being developed in CCAMLR and the IWC.