This paper presents the latest developments in Casal models for Crozet with an updating of input data from the more recent years (up to 2015/16 season) and a reassessment of stocks taking into account the previous remarks of the WG-FSA meetings.
In 2015, An Icefish specific trawl survey was undertaken at Kerguelen Islands (Division 58.5.1) to collect information about the size distribution and the biomass status of mackerel icefish, Champsocephalus gunnari. Data from this random stratified trawl survey was used for a short term assessment of C. gunnari on Kerguelen EEZ. The standard CCAMLR methods were used to provide potential yields, a catch limit of 8278 t is recommended for 2016 and 6701 t for 2017.
Abstract:
An updated assessment of the Patagonian toothfish (Dissostichus eleginoides) stocks in Kerguelen area is presented. This study is based on a CASAL (C++ Algorithmic Stock Assessment Laboratory) model. Different statistical and biological datasets are used: catches, tag releases/recaptures data, commercial catch-at-length, data from the “PoKer” surveys, and the last age readings.
Abstract:
This paper is an update on exploratory fishing for toothfish by the New Zealand vessel San Aspiring pursuant to CMM 4.14, approved by the SPRFMO Commission in January 2016. This update is provided for the consideration of the SPRFMO Scientific Committee meeting in October 2016 such that it can advise the SPRFMO Commission meeting in early 2017 on progress with the exploratory fishery.
Abstract:
The WG-SAM in 2016 “agreed the importance of identifying a set of diagnostics and clear criteria to assess the likelihood that a vessel is operating as would be expected in normal research activities”, further noting that a characterisation of fishing activities was also required in order to achieve such a goal (WG-SAM 2016, paragraph 4.19).
In this paper, we further develop the analysis of Large et al. (2016), using fishing activities in the northern Ross Sea region as an example. We investigate the time taken to haul a line as a metric, and estimate vessel effects associated with fishing events such as research surveys. Results showed that individual vessels exhibited significantly different times to haul lines once standardised for other factors, but that the activities carried out as part of the SSRU 88.2A–B North survey were within the expected range for the vessels involved. Additional fishing activity metrics, combinations of those metrics, or area effects could be investigated by developing this methodology further.
Abstract:
This report provides a characterisation of the toothfish fishery and associated tagging programme in the Amundsen Sea Region (SSRUs 88.2C–H) up to and including the 2015/16 fishing year. A research plan was implemented in the region beginning in 2014/15 to concentrate fishing in the South (SSRUs 88.2C-G) into four smaller research blocks in order to increase the likelihood of recaptures of previously tagged toothfish. In 2015/16, a total of 9 inter-season tagged fish were recaptured in these research blocks, confirming the utility of this approach to recapture tagged fish, and providing key information on the size of the population. Furthermore, 11 tagged fish were recaptured in the north (SSRU 88.2H). The data provided in this paper form the basis for the data inputs into the stock assessment for the Amundsen Sea region.
Abstract:
This paper presents further progress towards a two-area stock assessment model for Antarctic toothfish (Dissostichus mawsoni) in the Amundsen Sea region, defined here as SSRUs 88.2C–H. The region is split into two main areas: the North (SSRU 88.2H) comprising large mature fish, and the South (SSRUs 88.2C–G) comprising a mix of large mature fish and small immature fish.
Two-area stock assessment models were first developed for the region in 2014 and refined in 2015. Results showed the need to collect mark-recapture data in the South to help inform the estimation of biomass in the South. We present an update on these two-area stock models, which include two years of new data collected under a research plan. The assessment models were fit to the proportions-at-age in the catch and the mark-recapture data from the two areas. The results suggest that the research plan is successful in starting to inform the model, and in particular the size of the fish population in the South. We recommend that the current research plan be extended for a further 2-year period so that additional mark-recapture data can be collected particularly from the South, and that the models be developed further in the interim period. We also recommend that all Members, where possible, contribute to the development of annual age-length keys, using agreed otolith reading protocols and aging validation.