CCAMLR

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.

Penguin censuses on the Antarctic Peninsula are often subject to logistical challenges that preclude nest censuses being conducted at the peak of egg laying as established by the CCAMLR Ecosystem Monitoring Program (CEMP) (Scientific Committee for the Conservation of Antarctic Marine Living Resources 2004). Additionally, the historical literature, necessary for establishing baseline conditions, also includes many census counts with non-standard timing. The challenge is, therefore, to correct ‘off-peak’ census counts to make them comparable with current standard methods. Census correction involves knowing 1) how the census is timed relative to the peak of egg laying and 2) how nest numbers change through the breeding cycle. In this paper we present an analysis relating to both of these two challenges. Clutch initiation dates for four penguin breeding sites are examined (Cape Shirreff, Livingston Island (62°28′ S, 60°46′ W), Admiralty Bay, King George Island (62°10′ S, 58°30′ W), Humble Island (64°46′ S, 64°06′ W), and Petermann Island (65°10′ S, 64°10′ W)) in relationship to potential drivers of clutch initiation (e.g. temperature, precipitation, sea ice, sea surface temperature, etc.). We find that mean October temperatures constitute the most consistent significant factor related to the timing of clutch initiation in all three of the penguin species examined (Adélie, gentoo, and chinstrap). We present a statistical model for determining the peak of clutch initiation for any given year and site and, along with a simple estimation of species-specific nest attrition rates, we use this model to step through the procedure for correcting off-peak census counts.

This paper reports the results of a ground survey of fur seal colonies from in the South Shetland Islands in 2007/08. Multiple counts of pups at each colony were conducted to establish confidence limits on pup production. Total pup production was 7,602 (±103) pups down 24.4% from the last census in 2001/02 (10,057 ±142 pups born). Dead pups accounted for 1.64% of the total. A comparison with previous censuses over a 20yr period (1987, 1992, 1994, and 1996) indicates the rate of increase in fur seal populations has diminished substantially. The averaged annual rate of increase from 1987-1994 was between 13.5-13.9%. From 1994-1996 it was 8.5% and from 1996-2002 the average annual rate was +0.9%. Since 2001/02, pup production for the entire archipelago declined at an average annual rate change of -4.3%. Sources of error in pup production estimates include unobserved neonate mortality prior to census, natality rates of the adult female population and leopard seal predation on pups. Neonate mortality up to 30 days after the median date of pupping was estimated for the years 1997-2007 at 4.5% (±0.60). Adult female natality for the same period was 0.79 (±0.02) and in 2007/08 was below average at 0.73. Leopard seal predation was estimated from the rate of mother-pup failed pairs after pups begin entering the water (~30d after the median date of pupping [MDP]). Leopard seal predation for the first 75d post MDP for 2003-2007 was estimated at 0.376 (±0.043) and for the 2007/08 was above average at 0.522. Thus, higher neonate mortality, reduced natality, and an increase in leopard seal predation all contributed to lower pup production estimates in 2007/08.