CCAMLR

We present a preliminary analysis to estimate the consumption of prey by Adélie penguins Pygoscelis adeliae in Subareas 48.1 and 48.2 during the period when penguins are constrained by breeding. We parameterised our analysis using data from the population of Adélie penguins breeding at Signy Island, South Orkneys. We show that the highest levels of consumption occur during the crèche and pre-moult period, consistent with similar studies of Adélie penguins breeding in East Antarctica. On the basis of variable breeding success and the proportion of krill and fish in their diet, we estimate that the population of Adélie penguins at Signy Island consumes 4,600 t of krill and 696 t of fish during a breeding season. Based on this we estimate Adélie penguins in Subareas 48.1 and 48.2 respectively consume 304,980 and 53,161 t of prey during a single breeding season. Our study builds on previous work using a similar methodology to assess the consumption by macaroni penguins in Subarea 48.3. We report that further analyses will be undertaken for other krill-eating penguin species in Area 48, in particular chinstrap P. antarcticus and gentoo P. papua penguins.

The inter-vessel variability of krill distribution in the catches obtained in the Bransfield Strait (SSMU APBSW and APBSE) in April and May 2014 and 2015 was analyzed. The presence of statistically significant differences in the krill length distributions from  catches obtained by the vessels operating in the fishing grounds with spatio-temporal overlapping is shown. At the same time, significant differences exist both for vessels using the same trawl fishing method and for vessels operating with different fishing methods. The inter-vessel variability of krill length in the catches is more pronounced with respect to the length distribution (content of young and large specimens), and to a lesser extent to discrepancies in the weighted mean length estimates per SSMU by month and vessel.

An analysis of spatio-temporal variability of CPUE indices in the krill fishery in subarea 48.1 by years and small-scale management units, including inter-annual, monthly and inter-vessel variability with account of the fishing method used is presented. Particular attention is paid to the fishery in the Bransfield strait, where the main fishery in Subarea 48.1 is concentrated  The possibility of using the standardized CPUE indices as krill biomass density indices for monitoring the variability of krill biomass in SSMU during the fishing season is discussed. Variability of monthly average standardized CPUE estimates in the Bransfield strait shows that despite intensive fishery the density of krill biomass during the fishing season did not decrease and even often increased there.  The latter is an evidence of krill biomass replacement and supplement during the fishing season due to geostrophic drift, and this also points to unjustified hypothesis on the fishery effect on krill biomass and dependent predators.

Norway is in the process of extending its monitoring efforts in the area around South Orkneys by deploying acoustic moorings in a commercially exploited area. Data gathered from the moorings will be used to parametrise models, in order to gain better understanding of the interaction between ocean physics and behaviour in driving krill biomass variation in the area.

The Antarctic minke whale (Balaenoptera bonaerensis) is the most abundant baleen whale species in the Southern Ocean. Quantitative information on prey consumption of whales is useful to understand their feeding ecology and role in the Antarctic marine ecosystem. The purposes of this study were 1) to investigate the feeding habits of Antarctic minke whales based on information on prey species in stomach contents, and 2) to estimate the amount of prey consumed by whales, accounting for some uncertainties. The analysis is based on the data from whales taken by JARPA (Japanese Whale Research Program under Special Permit in the Antarctic: 1989/90-2004/05) and JARPAII (2005/06-2013/14) in the Indo-Pacific region of the Antarctic (35°E-145°W). Sampling of Antarctic minke whales was conducted in the austral summer seasons, mainly in the months from December to March. The Antarctic minke whales fed mostly on Antarctic krill (Euphausia superba) in offshore area, and on ice krill E. crystarollophias in coastal (shallow) area on the continental shelf such as the Ross Sea and Prydz Bay. Daily prey consumption by the whales in each reproductive status group was estimated using an energy-requirement approach. Based on the results obtained by three equations combined and Monte Carlo simulations, the daily prey consumptions per capita of Antarctic minke whales were 207.1kg and 353.3kg for immature and mature males; and 229.3kg and 397.0kg for immature and mature females, respectively. The CVs of the daily prey consumption consumed by whales per capita were in the range 0.35-0.39. Consumption was equivalent to 4.9-6.3 % of body weight. The total per capita prey consumptions during the feeding season were 24.8 and 42.4tons for immature and mature males, 27.5 and 47.6tons for immature and mature females, respectively. Total prey consumptions of krill by Antarctic minke whales during the feeding season (120days) were estimated at 1.5 and 4.6 million tons in Areas IV and V, respectively. It is expected that the output of this study will assist the understanding of the role of the Antarctic minke whale in the ecosystem and development of ecosystem models.

The composition of penguin diet is currently monitored through the A8 CEMP Chick Diet monitoring parameter. The current Standard Method involves stomach lavage to collect the stomach contents of adult birds and sorting the samples to identify prey composition and mass. At WG-EMM-12 it was noted that Australia had stopped collecting penguin diet samples and that alternative, less invasive, procedures were under consideration. Here we discuss results from recent work using the extraction of prey DNA from penguin faecal samples as an alternative, non-invasive procedure. We describe the technique, discuss recent results and outline current thoughts on its advantages and limitations. We also outline a validation study currently underway on samples collected at Signy Island, South Orkneys, to compare the prey DNA from faecal samples and stomach lavage techniques.

Estimating the consumption of prey by higher-order predators is a priority for WG-EMM as an element in CCAMLR’s ecosystem-based approach to management for the krill fishery in the Southern Ocean. Previous assessments of prey consumption for seabirds have focussed on breeders using data recorded at the breeding colonies. However, recent work suggests that the size of the non-breeder component of an Adélie penguin population can be substantial compared with the size of the breeder population. This paper describes the extension and parameterisation of a bio-energetics model developed to estimate prey consumption by breeding Adélie penguins to include estimates of prey consumption for the non-breeder component of an Adélie penguin population. Given an estimate of non-breeder abundance, this development allows consumption to be estimated for the total population.

We outline progress on current work aimed to improve estimates of flying seabird abundance, and ultimately krill consumption, from land-based breeding bird counts of five species (Antarctic petrel, Cape petrel, southern fulmar, snow petrel and Wilson’s storm petrel) in Divisions 58.4.1 and 58.4.2. We compiled information on the historical search effort in potential seabird breeding habitat in these Divisions and conclude that only 2-3% of potential flying seabird breeding habitat has been searched for breeding populations. We conclude that a compilation of historical population counts where searches have been made substantially under-estimates the true breeding populations across all habitat, and alternate approaches are required to realistically estimate seabird abundance, and from that consumption. This conclusion is supported by preliminary results from a broad-scale sample survey of snow petrels. This work is an important contribution to estimating krill consumption by predators in Divisions 58.4.1 and 58.4.2 as part of a risk assessment for these Divisions. It complements similar work on other predator groups in the region including pack-ice seals and Adelie penguins and will contribute to estimating total krill consumption by these predator groups.

We provide a brief update on the progress of our CEMP Special Fund project ‘Developing an image processing software tool for analysis of camera network monitoring data’. The project was initiated with support from the CEMP Fund in 2015/16. A software programmer has been engaged and is currently working within the Australian Antarctic Division’s Data Centre to refine the software and develop post-processing code according to specifications developed in consultation with the CCAMLR camera user community. We expect to complete a package of software and post-processing code by early 2018.

The distribution and abundance of krill aggregation inhabiting the Subarea 48.1, which includes the Elephant Island peripheries and the west and south of the South Shetland Island, were estimated using an acoustics survey. Acoustic data were collected with 38 and 120 kHz from April 13 to 24 in 2016 and 38 and 200 kHz from March 6 to 14 in 2017. Krill were collected by the commercial middle trawl fishing vessel. The data were processed and analyzed following CCAMLR standard protocols using swarm integration (SHAPES module within that software for swarm identification) based on data from a transect-based survey. The weighted krill density and biomass were estimated to be 0.20 g/m² and 18 thousand tons (CV=33.8%) applying S_v difference 3.96-5.91 dB and 0.92 g/m² and 83 thousand tonnes (CV=31.4%) applying S_v difference -3.0-13.8 dB in 2017, respectively. Krill density and biomass were significantly higher in 2016 than those in 2017.