CCAMLR

There is presently debate over the degree to which the fishery for Antarctic toothfish (Dissostichus mawsoni; ‘toothfish’) in the Ross Sea may affect the ecological viability of top predators such as Weddell seals (Leptonychotes weddellii), but available evidence remains inconclusive as a result of both methodological limitations and knowledge gaps.  We present new stable isotope data on Weddell seal prey, consider the assumptions underlying application of stable isotope methodology to Weddell seals, and estimate the potential contribution of toothfish to the diet of Weddell seals using an isotope mixing model.  As a new approach, we also estimate Weddell seal food requirements by considering nutritional quality of potential prey species including toothfish in the context of updated estimates of Weddell seal energy requirements.  The energy density of potential prey items (fish and invertebrates) covers a four-fold range.  Nutritional analysis of Ross Sea prey suggests that toothfish may represent a unique high-energy food resource for Weddell seals that possibly cannot be adequately replaced by other prey, in particular during periods of high energy demand such as late-stage lactation and the post-breeding recovery of body weight and condition.  The assumed dominance of Antarctic silverfish (Pleuragramma antarcticum) in Weddell seal diets should be re-examined given the known biases of methods used to derive diet estimates.  While large (>30 g) silverfish occurring at high densities are a valuable nutritional resource, smaller size classes are unlikely to be adequate to meet the estimated energy requirements of adult Weddell seals.  Our ability to conclusively determine possible dependence of Weddell seal populations on toothfish, and hence possible impacts of toothfish removal by fisheries, is primarily hindered by (a) insufficient information on Weddell seal diet, due to inadequate temporal coverage and biased methodology, and (b) uncertainty regarding Weddell seal abundance and spatial foraging patterns in the Ross Sea region.

We present new censuses data for a suite of chinstrap (Pygoscelis antarctica) and gentoo (P. papua) penguin colonies in the Cierva Cove region of the Danco Coast, including ASPA No. 134. Data indicate an overall increase in breeding population size of chinstrap and gentoo penguins. Given positive population growth in recent years in this rapidly changing environment and a position within Area 48 that is, relatively speaking, lightly fished, we suggest that the Cierva Cove colonies provide an opportunity to explore how monitoring data can provide useful contrasts to other monitoring sites with more fishing activity.

Understanding the temporal variability in vital rates (e.g. growth and survivorship) of wild populations is practically and statistically difficult but crucial for connecting such variation to mechanistic drivers and their population consequences. For somatic growth, empirical estimates of variation are rare because they often require expensive long-term tag-recapture programs. In marine pelagic ecosystems, where many species are difficult to sample and not amenable to tagging studies, researchers have relied on estimating growth from length-frequency distributions. We developed a general approach for estimating growth from observed length-frequency samples by combining kernel density estimates of the length-frequency distribution and the von Bertalanffy growth function. Our approach is conceptually straightforward and easy to implement. We applied the methods to Antarctic krill Euphausia superba collected from the Southern Ocean over a span of 19 yr to document among-year variation in krill growth during the austral summer. Our estimates of growth align closely with existing estimates of growth, but we provide the first estimates of among-year variation in krill growth. We estimate very high among-year variation in growth (annual estimates for a 30 mm krill in the Elephant Island region ranged from 0.00 to0.17 mm d −1 ; mean = 0.073, among-year coefficient of variation  ≈ 0.8). We correlated growth rate variation to estimates of ocean chlorophyll but not to other oceanographic indices, contrasting with results from previous studies. The large amount of variation in growth unexplained by environmental  covariates  has  substantial  implications  for  ecosystem  management  in  the  Southern Ocean ecosystem.

This paper introduces a proposed data integration and assimilation tool to assist the CCAMLR Ecosystem Monitoring Program in obtaining policy-relevant summaries of Adélie penguin abundance and distribution. The engine of this decision-support tool is a physically-based algorithm for retrieval of continent-wide Adélie penguin distribution and abundance from satellite remote sensing imagery. An ecologically-based Dynamic Bayesian Network (DBN) model assimilates remote sensing results streaming in from a multitude of sensors with other sources of information such as field counts and predictions from state-space models of population change. The DBN model synthesizes this data flow into policy ready metrics of Adélie penguin abundance at any user defined spatial or temporal scale. The results will route through a browser based geospatial application custom designed to address the needs and concerns of the Antarctic research and management community. In sum, we propose to develop the data-to-knowledge pipeline required to fully harness the power of remote sensing for effective resource management in the Antarctic. This paper serves as an introduction to our proposed development work (as recently submitted in response to NASA Research Announcement NNH12ZDA001N-ECOF) and a request for input on the design of the associated user interface.
 

The authors analyzed the spatial-temporal structure of standardized indices of catch per effort unit (CPUE)  of Antarctic krill fishery in the Area 48    in  relation to dynamic of ААО indices (Antarctic Oscillation Index) as one of the factors used in analysis of inter-annual and long-period fluctuations of hydrometeorological conditions at high latitudes of the southern hemisphere.  Standardization of CPUE values was calculated on the basis of generalized linear models method with mixed effects (GLMM). Analysis of the time-series of CPUE and AAO indices were carried out using the modern de-nosing data methods, including wavelet transform, Markov’s regression model to determine the fishery regime shifts and multivariable wavelets de-noising. The influence of climate variability was traced in the long-term dynamics of fleet operation including standardized indices of catch per effort unit (CPUE), monthly catches and catches per vessel day.  It was shown that the most important evidence of ongoing climate variability is the fishery regimes switching observed in long-term fishery in the Area 48. It was found that the most significant switching of fishery regime occurred in 2006-2011, when fishery had transferred to the state «high CPUE». This period is characterized by the highest values of CPUE and AAO indices for the whole observation period 1985-2011.  Analysis of krill fishery indices obtained with using different fishing technologies revealed that the “high CPUEs” regime is not associated with the changes in fishery technology and using the continuous fishing method, but is due to the influence of the current climatic changes.

A meso-scale zooplankton and krill net sampling survey was carried out in the north-western Weddell See and in Bransfield Strait/western Antarctic Peninsula during late January to early March 2013. The aim of the survey was to study the zooplankton composition and krill abundance and distribution in the outflow region of the Weddell Sea. Due to severe pack-ice conditions, more than half of the survey area was covered by ice during the summer season. Antarctic krill densities were found to be highest in the western Peninsula region and lower in ice-covered Weddell Sea waters. Overall krill density was below the longterm average of the area. New one-year-old recruits were scarce, the stock was dominated by two and three year old krill. Spawning occurred late and numbers of gravid females and larvae were low. Ice krill E. crystallorophias was abundant on the shelf of the north-western Weddell Sea. Thysanoessa macrura and salps Salpa thompsoni were far less abundant than the longterm average and were confined to the more northern, ice-free areas.