The Workshop for the Analysis on the Anomalously High CPUE by Korean Vessels in the CCAMLR Area, organized by the Ministry of Oceans and Fisheries of Korea with the assistance of the CCAMLR Secretariat, took place from April 29th to May 1st, 2013 in Busan, Korea. Key issues raised and future work suggested at the Workshop are described in the report.
Abstract:
The Spanish vessel Tronio started the research plan in the 2012/13 season using the Spanish bottom longline system. One depletion experiments was completed in each of the SSRU surveyed (58.4.1H and 58.4.1G). Three prospecting-phase clusters of sets did not reach the established threshold to start the depletion.
A prospective estimation of the local biomass (BLOC) of the two localized areas where the depletion experiments were performed is done as well as an estimation of the biomass of the SSRUs (BSSRU), maximal and minimal, considering areas with high and low densities.
A summary of the activities and results from the survey is also presented related to the sampling scheme, collected samples and species involved.
There is no abstract available for this document.
Abstract:
Research and monitoring (RM) plans need to be developed for marine protected areas in an interdisciplinary way which includes scientific knowledge, ongoing and future collaborative projects and management expertise. In 2012, the Working Group on Ecosystem Monitoring and Management considered a number of issues relating to the development of RM plans, including that guidance is needed from the Scientific Committee and Commission in the detailed structure of the plans. SC-CAMLR endorsed advice from WG-EMM that RM Plans needed to relate to the requirements for an MPA and that the research and monitoring should be achievable in practice. The proposal for the East Antarctica Representative System of Marine Protected Areas (EARSMPA) contains the priority elements of the RM Plan to support the management of that system. Here, we show how the scientific initiatives currently underway in the region could be used as a foundation for a RM Plan for the EARSMPA. All Members are invited to participate in the research and monitoring activities, particularly through these initiatives. This paper is structured to first provide the text from the draft conservation measure for the EARSMPA on the priority elements of the RM Plan. Second, summaries are provided of initiatives currently underway that could provide research and monitoring in the region. Last, we assess which parts of the RM Plan would benefit from the outcomes of the initiatives.
Abstract:
As part of the Secretariat task to ensure the quality and consistency of the data arising from the CCAMLR SISO, an algorithm was designed to automatically import and check data entered by observers in their logbooks. A first version of the algorithm was tested on four randomly selected longline fishery logbooks. In its current version the algorithm is able to detect and report invalid data formats, as well as value inconsistencies through a limited set of logical tests. For each logbook inspected, a text report indicating the locations of faulty entries, a set of figures to display length and weight of toothfish, and, an overall data entry quality score, are automatically generated. The first results highlighted some recurring issues, such as the addition of rows or columns of data within worksheets, which displaces data and results in the importation of the wrong data by the algorithm and invalidates automated data processing routines.
Abstract:
Proposed Research plan for the survey of Ukrainian longliner in 48.2 subarea.
Abstract:
The Scientific Committee has provided detailed advice on the preparation and evaluation of research plans in data poor fisheries submitted under CMs 21-02 and 24-01 in 2011 and in 2012. We formulate advice arising from extensive Working Group discussions and highlight additional design and implementation issues raised during research plan design and evaluations. Our aim is to streamline the review process, promote quality research designs, and make the proposed catch limits more explicit with regard to the inherent trade-off between quickly developing quality stock assessment input data and potential biological risks arising from uncertainty in the research implementation process.
Abstract:
Toothfish stock assessment results are strongly influenced by tag-release and tag-recapture data, and rely on the assumption that tagged and untagged fish have constant probabilities of recapture regardless of the spatial distribution of releases or subsequent fishing effort for recaptures. Conceptually this assumption implies either that tagged and untagged fish mix equally in the population, or that fishing effort for recaptures is distributed in proportion to the underlying abundance. Neither of these conditions are likely to occur in practice, and violation of this assumption may lead to bias. In this paper we investigate such potential biases in the assessment of Antarctic toothfish in the Ross Sea fishery using simulated outputs from spatially explicit operating models.
Two spatially explicit operating models were developed: each was comprised of 189 discrete cells, with a cell size of about 25,000 km2. The first model was restricted to those locations of the Ross Sea region that have been fished (restricted model), and the second model extended to encompass all areas (unrestricted model). Simulated observations were generated from these models, and used as inputs into a simplified non-spatial stock model based on the 2011 Ross Sea toothfish stock assessment.
Results suggested that the assessment model was biased low by 17% or 43% assuming movements defined by the restricted and unrestricted models respectively. The bias was thought to reflect the underlying distributions of tag-releases and subsequent fishing effort, and the limited mixing of fish between areas — more than half of tags have been released (and subsequently recaptured) from SSRUs 88.1H and 88.1I, while a large proportion of the fish are in remaining SSRUs where fewer tags were released and with lower fishing effort. This effect is accentuated in the unrestricted model, where about half of the fish are distributed in areas that had not been subject to fishing effort.
We note that the extent of bias will depend on both the proportion of fish in unfished areas and movement rates between fished and unfished areas, but that misspecification of other parameters in the assessment models (for example tag mortality rates and tag detection rates) or alternate spatial hypotheses may also introduce biases that we have not considered in this paper. While additional analyses need to be undertaken to confirm or improve the spatial models used here and alternative movement hypotheses should be tested, we consider that these simulation experiments provide a useful tool to evaluate potential bias and uncertainty in our understanding of the assessment in the Ross Sea toothfish stock and potentially similar tag-based assessments elsewhere in the CCAMLR Area. They are also useful in investigate the likely consequences of management strategies for stock assessments, including changes in fishing effort or tagging distributions. They can also be used to investigate the potential effects of alternative biological hypotheses for less well defined parameters, for example maturity and natural mortality rates.