The research fishing proposal for Dissostichus spp. in Subarea 48.6 and Divisions 58.4.1, 58.4.2 and 58.4.3a is resubmitted following paragraph 3.24 of WG-SAM-12. In the present proposal, we firstly showed information of catch, efforts, tagging experimental results based on the CCAMLR C2 data, and secondly showed the results of biological features with some discussion of life history in data-poor fisheries mainly using CCAMLR Biological data. Finally we made the proposal for the operations in the 2012/13 season for all vessels.
Catch and efforts were active in two areas in the north of Subarea 48.6, two areas in the south of Subarea 48.6, one area in Division 58.4.2, five areas in Division 58.4.1 and one area in Division 58.4.3a. In these areas, number of tags available for recaptures in 2013 was also higher. Recaptures were made also within these areas but those for D. mawsoni were scarce, especially in Division 58.4.2. Nominal CPUE in terms of weight of D. mawsoni in the south of Subarea 48.6 is two times higher than those in other areas.
According to the distribution of CPUE for small size groups, the west of Prydz Bay region seemed to be an important area for pre-adult D.mawsoni as reported previously. From the seasonal variations in development of GSI, the north of Subarea 48.6 is one of important spawning grounds for D. mawsoni, however, self-sustaining population may not exist in these areas because of very small proportion of immature fish. Highest GSI for D. mawsoni in March over years was observed in the shelf area at approximately 100°E (SSRU 58.4.1 C), which is consistent with previous report. The increase in abundance of fish with small sizes in SSRUs B and C of the south of Subarea 48.6 speculated the extension of the Weddell Sea population. The clarification of life history in data-poor fisheries may need more information of biological features in the wide areas including Weddle Sea and Ross Sea regions.
From the number of tags available for recaptures, a total of 12 blocks (aggregation of 1° longitude x 30’ latitude box) for research is produced over the data-poor fisheries area for all vessels. The research should be fundamentally conducted within the blocks. However, in case research hauls in the blocks along the ice-shelf area cannot be done sufficiently due to sea-ice and small number of fish caught etc., the vessel may operate at neighboring available area and accumulate tagged and released fish to clarify the migration of fish, biological feasters such as distribution of developmental and maturity stages, sex ratio, age-length relationship, and catch rate which help the progress in assessment of stock status.
Estimations on expected numbers of recaptures suggested that the increase of current catch limits may be needed to increase in success of the mark recapture research for D. mawsoni in the south of Subarea 48.6 and Divisions 58.4.1 and 58.4.2.