CCAMLR

During the breeding season, Antarctic fur seals are central-place foragers, ranging from their colony to feeding areas hours to days offshore, returning periodically to suckle. Outside of this, little is known about a female’s foraging strategy, her success upon which depends not only her survival but that of her young. As such, a fundamental component to understanding the survival and reproductive success of fur seals is to identify habitat preferences. Our objective was to characterize the distribution and range of foraging females rearing pups at Cape Shirreff, Livingston Island, Antarctica. We instrumented 95 females with ARGOS satellite-linked transmitters prior to departures on foraging trips from late December to late February for four consecutive breeding seasons (1998/99-2001/02). We had 7,550 successful at-sea satellite locations (mean: 12/day/female, SE±0.11), after the data were filtered to eliminate positions that required females to travel >4m/sec. Foraging trip lengths averaged 4.0 days (SE±0.11). The mean range traveled offshore was 83.3km (SE?2.9) and the maximum distance was 369.1km. Foraging trip length was positively correlated with both foraging range (r2=0.48, F1,169=157.73, P

Antarctic fur seal pup growth studies presented and reviewed by WG-EMM-01 led to discussion on the need to modify Standard Method C2: Pup growth. The issues discussed relate to the timing of sampling and the selection of animals to weigh. The following is a proposal on how the protocol and reporting should be changed to facilitate future inter-annual and inter-regional comparisons of fur seal pup growth.

Discovered in 1819, the South Shetland Islands soon became the focus of intensive sealing efforts. Abundant, but never quantified, Antarctic fur seal populations were exterminated by 1874 and did not begin re-colonizing until ~80yrs later. The first reported pups born post-exploitation were found at Cape Shirreff, Livingston Island in January 1960. In 1987, an archipelago-wide aerial and ground census identified breeding colonies and substantial increases in pup production. This paper reports the results of a ground survey of all known fur seal colonies from Smith to Elephant Islands from 30 January –5 February 2002. Multiple counts of pups at each colony were conducted to establish confidence limits on pup production. Total pup production was 10,057 (±142); 85% were from Cape Shirreff (64%) and San Telmo Islands (21%). Dead pups accounted for 1.37% of the total. A comparison with previous censuses over a 15yr 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%. Pup production at individual colonies varied with some increasing and others decreasing. The San Telmo Islands had the largest decline from 2684 pups in 1996 to 2124 in 2002 (-3.5%/yr). Pup production at Cape Shirreff increased from 4968 to 6453 pups (5.0%/yr) during the same period. Cape Lindsey, Elephant I., and the Seal Islands had averaged annual declines of –9.4 and -6.3% from 1996-2002.

A model was recently proposed to predict the target strengths (TS) of Antarctic krill, Euphausia superba, versus incidence angle (?) [McGehee et. al, 1998, Deep Sea Res. Pt2, 45(7)1273-1294]. Based on the distorted wave Born approximation (DWBA), the model depends upon the coherent summation of scattering from elements of a discretized bent cylinder. It was empirically validated at 120 kHz near broadside incidence (? ? 90°), but large discrepancies were observed at other angles away from the main lobe. As the side-lobe measurements were both higher than the model predictions and above the noise floor, the authors noted that the differences were not entirely due to noise. In this study, the accuracy of the DWBA model is further explored. Results indicate that phase variability in the scatter from elements of a discretized bent cylinder (krill model) causes a dramatic flattening in the side-lobe regions of TS(?), while negligibly affecting the main scattering lobe. These results are consistent with the krill TS measurements in McGehee et al. (1998). Thus, by accounting for phase-variability in the solution of the DWBA model, a more accurate and thus practical tool is developed for predicting krill TS.

Total scattering cross-sections (st) of Antarctic krill, Euphausia superba, were acoustically measured over a broadbandwidth (36 to 202 kHz) using a new technique [J. De Rosny and P. Roux, 2001, J. Acoust. Soc. Am. 109(6): 2587:2597]. From 18 February to 9 March 2002, mean total target strengths ( ??10log(??4?) t TTS ), were measured from groups of 57 to 1169 krill (average standard length = 31.6 mm; standard deviation = 6.6 mm), at the Cape Shirreff field station, Livingston Island, Antarctica, and aboard R/V Yuzhmorgeologiya. Chirp pulses were sequentially transmitted with an omnidirectional emitter into one of three glass carboys containing groups of krill swimming in 9.3, 19.3 or 45.9 l of seawater ( 0.6 ??temperature??3.6 °C). Between each pulse, the krill moved within the fixed-boundary-tank and the modulated reverberations were sensed bi-statically with three omnidirectional receivers. At each center frequency (fc), the coherent energy in 200-pulse ensembles identified sound scattered from the tank. The incoherent energy described total sound scattering from the krill. Thus, the TTS at each fc was extracted from a correlation analysis of energy reverberated in the tank. Measurement accuracy was determined using standard metal spheres for references [Demer et al., in-press, J. Acoust. Soc. Am.], and the precision was estimated from the variability in krill TTS measurements. Moreover, empirical estimates of mean s t were statistically compared to a recently proposed krill scattering model based on the distorted wave Born approximation (DWBA) [McGehee et. al, 1998, Deep Sea Res. Pt2, 45(7): 1273-1294], which has been enhanced to account for the stochastic nature of sound scattering (SDWBA) [Demer and Conti, submitted, ICES J. Mar. Sci.], and integrated over all scattering angles (SDWBATTS). This study improves upon methods for acoustical identification and target strength estimation for Antarctic krill, thus reducing the uncertainty in biomass estimation using multi-frequency echo sounder data and echo integration methods.

Demographic parameters (age-specific mortality rates, fecundity levels and population numbers) were analysed for the Béchervaise Island Adélie penguin colony in eastern Antarctica after 12 years of CEMP monitoring. A life table was constructed, and predicted rates of population growth and breeding success calculated. As for most long-lived seabird species, growth/decline rates of the Adélie penguin population at Béchervaise Island were found to be more sensitive to changes in annual survival rates, especially of young breeding adults, than to changes in fecundity parameters. These findings are discussed briefly in relation to other CEMP parameters, environmental factors and fishery regulation.

Seven fledging Adélie penguin (Pygoscelis adeliae) chicks and four post-moult adults were satellite-tracked using the Argos system during the winters of 1995-97 and 1998 respectively. Six fledglings departed from Béchervaise Island near Mawson station (67°35'S, 62°49'E) during late February 1996 and 1997 and were tracked for up to five months before transmissions stopped. The seventh chick left Magnetic Island near Davis station (68°33'S, 77°54'E) in February 1995 and was tracked for 32 days. All fledglings travelled northward initially, then westward along the edge of the fast-ice or in the pack-ice. Fledglings had travelled between 536 and 1931 km to the west of their natal colonies by the time transmissions ceased. Adult Adélie penguins were tracked between March and October 1998, following completion of their annual moult at Bechérvaise Island. Instruments were factory-set to transmit intermittently for the first five months and one day in four thereafter. Adult birds travelled westward until July after which time they moved north within the expanding pack-ice into known areas of high krill concentration before returning eastward toward their breeding sites. Penguin movements over the winter months were closely related to those of sea-ice in the region. Ice motion patterns were in turn influenced by gyral oceanic current systems and wind. We propose that large gyral oceanic systems provide a means for Adélie penguins to reduce costs of transport as they travel into regions of high productivity during winter and return to their breeding colonies in spring. Locations of boundaries of oceanic gyres may thus be useful to CCAMLR in the regulation of the Antarctic krill fishery as a means of delimiting management regions.

We examined temporal variability in a series of CEMP parameters collected over the period 1991/92 to 2001/02 on Adélie penguins at Béchervaise Island. Parameters relating to chick survival (brooding counts, 2/3 crèche counts and fully crèched chick counts) show large temporal variability while the other parameters were more stable. We also explored the correlation between CEMP parameters, and the correlation of each parameter with breeding success. Breeding success was measured in terms of 1) the absolute number of chicks on the island which fully crèche and 2) the number of chicks crèched per nest with eggs. We found a low degree of correlation between incubating and brooding nest counts which supports the notion that events occurring during the hatching period are crucial for chick survival. The sex of the foraging birds and the timing of foraging trips were important in determining whether foraging trip duration was correlated negatively to breeding success. Additionally, we examined within season penguin weights, the simplest output from the Automated Penguin Monitoring System (APMS), in terms of their correlation with breeding success. This analysis showed that lower weights of females at the time they depart after egg laying would appear to be the first indication that a season may have low breeding success. The results obtained throughout these analyses indicate that knowledge of the sex of birds is important for understanding interrelationships between CEMP parameters and breeding success.

In 2000 WG-EMM discussed the need for region-wide and circum-Antarctic estimates of abundance of land-based predators. At the 2001 meeting of WG-EMM it was proposed that a workshop be held in 2002 to assess the feasibility of such broad-scale surveys, and a small intersessional correspondence group was formed to scope out the terms of reference and method of operation for the workshop. The intersessional group developed a draft decision-making framework for planning regional scale surveys and agreed that it be applied at the workshop to a selected region as a means of both assessing and/or developing the framework and undertaking preliminary plans for the region. The framework is designed to be general enough to apply to any species or scale, and addresses the issues of survey specification, survey design, review and use existing information, and estimation of availability (proportion of total population not able to be surveyed) as an integral part of the survey design. The framework also recognises that new technologies and methodologies need to be considered for use wherever possible.

Naganobu et al. (1999) had assessed variability in krill recruitment and density with hypothesized environmental factors; strength of westerly winds (westerlies) determined from sea-level pressure differences across the Drake Passage, sea ice cover and chlorophyll-a in the Antarctic Peninsula area during 1982-1998. They found significant correlations between krill recruitment and those factors. The westerlies were especially regarded as a key environmental index. Fluctuations in the westerlies across the Drake Passage were referred to as the Drake Passage Oscillation Index (DPOI).
We planned to extend time series of DPOI using historical data. We searched the historical data and found the time series since the 1950s until 1988 at the Web sites of the Carbon Dioxide Information Analysis Centre for Rio Gallegos and since the 1940s until 1998 at British Antarctic Survey for Esperanza. Here we calculated a time series of DPOI from 1952 to 1988 at this stage. Time series since 1988 will be soon calculated after obtaining appropriate data.
The total number of monthly data used from 1952 to 1988 was 420. The mean, median, and mode were 13.6, 13.8, and 14.0 hPa, respectively. The maximum, minimum, and range were 27.5, -6.4, and 33.9 hPa, respectively. The standard deviation was 6.2. Linear regression declined as a whole from 1952 to 1988. A time series of 3-month running mean suggested considerable seasonal variability of climate. A time series of 12-month running mean indicated various yearly changes without seasonal variability. High DPOI periods, not less than 16 hPa, were mostly observed in the period before 1964 and only in 1973 and 1986-88 after 1964. Low DPOI periods, less than 14 hPa, were continued longer after 1964. A low DPOI less than 10 hPa appeared in 1967 and 1980. Intervals between the years of low DPOI were generally observed for around 3 years except 6 years between 1958 and 1964.