CCAMLR

The current season (2014/15) is the final one of the first three-season research which began in 2013 in data-poor fisheries. In the present report, catch, effort and biological data recorded by all effective vessels were analyzed for the improvement of stock assessment in the research blocks. Based on the result, the next three-season (2016-18) research plan in Division 58.4.2 is also presented.

The stock sizes for a research block (58.4.2_1) were estimated by the Petersen estimator and the CPUE x seabed analogy method using updated CCAMLR C2 data and reference area sizes.

The occurrence of juvenile fish for each ice shelf block suggests that the recruitment occurs along the ice-shelf zones of Subarea 58.4.2, especially SSRUs 58.4.2C and 58.4.2D. The GSIs during the austral summer over years tend to be more progressed in SSRU 58.4.2A.

Understanding of the resource structure through clarification of their life history is essential to establish stock assessment and robust stock/ fisheries management of Dissostichus spp. population(s) in data- poor exploratory fisheries. During the second three-season research, we will continue enhanced tagging program, and collection and analysis of biological data including otoliths and gonads to clarify migration route and associated life stages of the fish.

To this end, we propose to follow the current research style in the current research blocks for the second three-season research with the sample sizes estimated following the procedure recommended at the WG-FSA in 2013 in order to maximize the expectation of tag-recapture to the extent possible under the precautionary exploitation rate.

The current season (2014/15) is the final one of the first three-season research which began in 2013 in data-poor fisheries. In the present report, catch, effort and biological data recorded by all effective vessels were analyzed for the improvement of stock assessment in the research blocks. Based on the result, the next three-season (2016-18) research plan in Division 58.4.3a is also presented.

The stock sizes for block 58.4.3a_1 was estimated by the Petersen estimator and the CPUE x seabed analogy method using updated CCAMLR C2 data and reference area sizes. The stock size using the Petersen estimator was largely different from that using the CPUE method. Predicted numbers of tag recaptures from the estimated stock sizes using those methods were generally inconsistent with the observed number during 2013-14 seasons.

Understanding of the resource structure through clarification of their life history is essential to establish stock assessment and robust stock/ fisheries management of Dissostichus spp. population(s) in data- poor exploratory fisheries. During the second three-season research, we will continue enhanced tagging program, and collection and analysis of biological data including otoliths and gonads to clarify migration route and associated life stages of the fish.

To this end, we propose to follow the current research style in the current research blocks for the second three-season research with the sample sizes estimated following the procedure recommended at the WG-FSA in 2013 in order to maximize the expectation of tag-recapture to the extent possible under the precautionary exploitation rate.

In accordance with CM 21-03, Annex 21-03 A, attached are the net diagrams and marine mammal exclusion device diagram referred to in the krill fishery notifications for 2015/16 submitted for the three Norwegian vessels (Juvel, Saga Sea and Antarctic Sea). The pages 1 – 6 relate to the vessel Juvel, and the pages 7 – 10 relate to the vessels Saga Sea and Antarctic Sea.

In the 2012/13 fishing season Spain began implementing a multi-annual Research Plan for Divisions 58.4.1 and 58.4.2 in order to estimate local biomass of Dissostichus spp. by means of two methods: depletion and tagging. In 2014/15 the vessel was unable to conduct the proposed research experience due to problems with a blade of the propeller, During the season 2015/16 is intended to make the same proposed research with some minor changes, always subject to the ice conditions, fulfilling Spain's commitment to return to the same fishing areas in order to study inter-annual variability and maximize tag recovery, as well as, to progress research in these SSRUs (58.4.1H, G, D and C). Two research surveys have been already implemented in Division 58.4.1 and preliminary estimates of local biomass using Leslie depletion analyses have been obtained. Some recoveries of tagged toothfish have been made, both within-season and between-seasons recaptures and a preliminary Age-Length Key of Dissostichus mawsoni has been built after otholits reading from 58.4.1 division specimens. All these data will allow a robust stock assessment attempt by the end of this multiyear research survey.

Having accurate surface area estimates of toothfish (Dissostichus spp) habitats is important for CCAMLR in estimating the fishable biomass of these species in data-poor areas, developing scientific survey designs and models of habitat use.  Planimetric seabed areas (i.e. a two-dimensional surface) within the Convention area are commonly calculated, but surface area (i.e. a three-dimensional surface) is rarely estimated. The aims of this paper are to examine differences in: (1) planimetric seabed area based on different datasets (GEBCO 20014 and GEBCO 2008) and; (2) planimetric and surface area estimates for the same areas using the most up-to-date global bathymetry dataset (GEBCO 2014). Comparisons were performed at four different scales. At the coarsest scale areas were calculated within research blocks (all depths included), then estimates were limited to the fishable depth range of each research block (600-1800m included), the region were scaled down further to look at differences in eight depth classes and at the finest resolution areas were compared in individual (~500 m x 500m) grid cells within research blocks. Differences between the datasets varied between 0-62% depending on the research block and we considered the GEBCO 2014 dataset to be the most accurate so we used this in comparing different area metrics.  Results from the comparison of total surface and planimetric areas across all depths and the fishable depth range within research blocks showed differences of less than 2%. However, at the smaller grid cell scale, larger differences, of up to 137%, between the area metrics emerged. Given differences between surface and planimetric areas within fishable depth ranges at the scale of a research block were no greater than 2% this is not sufficiently different to impact toothfish biomass estimates based on the current CPUE-analogy calculations. However, in many of the research blocks a higher proportion of the grid cells within the fishable depth range (i.e. -600 - -800, -800 - -1000 etc.) had a greater surface to planimetric area difference than those cells that were outside of the fishable depth ranges. In those research blocks that showed larger difference at the grid cell level, it may be worth examining whether fishing occurred more frequently in cells with a large differences and if so whether deriving a more specific measure of surface area in fished locations (as opposed to the fishable depth range) impacts estimates of biomass. Spatial habitat modeling of toothfish species’ could also benefit from the use of surface area measurement at the grid cell level.