CCAMLR

The research fishing was conducted in Divisions 58.4.1 and 58.4.2 from 12 January 2017 to 14 March 2017 in 2016/17 fishing season. One additional national observer was on board to perform various scientific researches. The total catch of D. mawsoni was 153,084 kg with 4,360 individuals. The CPUE of D. mawsoni recorded 0.22 kg/hook. 805 individuals of D. mawsoni were tagged and released and additionally satellite archival tags were attached to 5 individuals of D. mawsoni. In Divisions 58.4.1 and 58.4.2, tagging rate with tag overlap statistics of D. mawsoni were 5.22 with 88% and 5.51 with 74%, respectively. Seven individuals of tagged D. mawsoni were recaptured. The research vessel, Kingstar has encountered unknown fishing gears during research fishing in SSRU G and E of the Division 58.4.1 and reported the information to the Secretariat. To get biological information of species, otolith, stomach contents, gonad and muscle were collected from each individual of D. mawsoni. Total 35 times of plankton sampling were conducted in the areas of Division 58.4.1 and 58.4.2. Two compact CTDs (Micro CAT, SBE37SMP) were used along with protective frames that would prevent the CTD connector from being damaged. Water temperature and salinity were collected from 33 data profiles during the survey in the areas of Division 58.4.1 and 58.4.2.

The third year research survey of Ukraine in subarea 48.2 by the fishing vessel SIMEIZ is finished. Ukraine proposes to continue survey in same boundary in same design for the next 2 year.

The assessment of toothfish in CCAMLR subarea 48.3 currently uses the first four years of tag recaptures post release as input data, whereas the assessment in subarea 48.4 uses all available recapture data (excluding in-year recaptures). A theoretical analysis of the use of data from double-tagged recaptures suggests that including recaptures from fish at liberty for long periods will introduce bias into the assessment. Sensitivity tests on both stocks show that this bias occurs in practice. Sensitivity tests on the 48.3 assessment show that this bias is not entirely explained by the effect of double tagging.

The existing bootstrap used in the assessment of icefish biomass in CCAMLR subarea 48.3 was compared to an alternative rescaled bootstrap to compare the performance of the methods. The differences between the method were small (less than 5%) except for slightly lower 5%iles in 2002 and 2004 in the rescaled bootstrap.

An integrated model was configured to estimate eighteen different subsets of 119 total parameters in alternative configurations of a model assessing the status and productivity of Antarctic krill (Euphausia superba, hereafter krill). We fixed the parameters that were not estimated in any given configuration at pre-specified values. The model was fitted to survey and fisheries data for krill in Subarea 48.1, a statistical reporting area used by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). The number of estimated parameters was gradually increased across model configurations. The numbers of parameters estimated in configurations that were able to obtain an invertible Hessian matrix ranged from 48 to 107. Groups of estimated parameters in each configuration were activated in seven sequential stages (the "phases") in a series of at least 20 replicate trials for each configuration. The parameter phases were assigned and reassigned randomly in each trial until an invertible Hessian matrix was obtained, or until 3,000 phase assignments had been completed for the replicate without obtaining an invertible Hessian. Model configurations were evaluated in terms of the total objective value, the maximum gradient, the proportion of replicate trials that found the minimum observed negative log-likelihood, and the number of iterations required in each trial series before obtaining an invertible Hessian matrix. Configurations that estimated more parameters fitted the data better, but the order in which the parameters were estimated became more important in finding the best fit as the numbers of estimated parameters increased. Phase-randomized replicates in configurations estimating many parameters were more likely to estimate values representing local minima than the lowest negative log-likelihood. The best observed estimates for the base configuration were obtained in about half of the replicates. Configurations estimating more parameters than the base configuration fitted the data better but either did not produce invertible Hessian matrices or had high maximum gradients. Diagnostics were applied to Markov chain Monte Carlo sampling in the best model of each configuration that obtained an invertible Hessian matrix to test for convergence to the equilibrium distribution.

The third year survey and observations of Dissostichus spp. in statistical subarea 48.2 on board the Ukrainian vessel SIMEIZ were conducted in accordance with the recommendations of the Scientific Committee and Commission. The third year survey design was slightly amended in comparison with the one of the second year and approved by WGs SAM, FSA and SC CCAMLR.  Obtained data will be used for the future biomass estimation of the target species and making decision for the future fishing on that fishing ground. 

The integrated assessment for Antarctic krill (Euphausia superba) in CCAMLR Subarea 48.1 has been under development since 2010. Progress on the model during this period was reported in a series of papers and presentations to WG-EMM, WG-FSA and WG-SAM from 2011 to 2016. The full text of the recommendations extracted from the CCAMLR Scientific Committee reports regarding the integrated krill assessment during that period is included as an Appendix to this document.

The purpose of this paper is to summarize the recommendations from CCAMLR Working Groups and the Scientific Committee that have been made to date along with a description of how the model has incorporated those suggestions, and to obtain advice from WG-SAM regarding whether the parameter estimation portion of the current model appears mature enough to use for representing the population/subpopulation represented by krill in Subarea 48.1, or, if not, what modifications or additions are required. This paper is focused on parameter estimation and does not include using the integrated model to make future projections to determine if candidate levels of harvest meet decision rules. The future projection components of the integrated krill model are undergoing revision following WG-SAM-2016.

In 2016, scientists from the USA and New Zealand undertook a collaborative initiative to deploy pop-off satellite archival (PSAT) tags on Antarctic toothfish (Dissostichus mawsoni) on the southern shelf (SSRUs 88.1M,J,L) and northern seamount (SSRUs 88.1B,C) areas of the Ross Sea region. The objectives  were to characterize movement and habitat preferences, compare two different commercially available types of PSAT tags, and to develop methods to support research and monitoring of the Ross Sea region Marine Protected Area. All fish were tagged as part of research longline efforts under CM 24-01 after the 2015/16 toothfish fishing season had ended. A total of 10 PSAT tags from two manufacturers were released on the southern Ross Sea shelf in the austral summer, and 5 PSAT tags were released on the northern seamounts in the austral winter, for a total of 15 PSAT releases. Of the 10 PSAT releases in the southern Ross Sea, data from two tags were reported via Argos (one with full data, one with partial). On the northern seamounts, two of 3 PSAT tags scheduled to pop-off on February 1, 2017 reached their housing crush depth (1800 m) shortly after they were released. Although some useful data was collected during this experiment, data recovery in general was poor. As this is a developing technology proposed to be implemented by a number of Members, we suggest that additional work, including product development, is urgently needed to develop best practice guidance for tagging toothfish with PSAT tags.