Workshop on the Development of Quantitative Assessment Methodologies based on Life-history traits, exploitation characteristics, and other relevant parameters for data-limited stocks (WKLIFE IV)
The fourth Workshop on the Development of Quantitative Assessment Methodolo-gies based on Life-history traits, exploitation characteristics, and other relevant parameters for data-limited stocks (WKLIFE IV), chaired by Carl O’Brien (UK) and Manuela Azevedo (Portugal) was held at IPMA, Lisbon, from 27–31 October 2014. The work conducted addressed five Terms of Reference concerning a collation of the sim-ulation testing of methods undertaken from 2010 to date and based on ICES work car-ried out in several expert groups, a comprehensive review of data-limited assessment methods and of simulation-tested HCRs that could be used in data-poor circumstances and the development of length-based targets, F-based proxies, size-based assessment methods within DLS and methods using survey data and MSY-based exploitation proxies for Category 3 stocks.
One of the primary conclusions from the simulation work undertaken to date is that the current widely used DLS category 3.2 HCR cannot be applied on its own, particularly when stocks are overexploited, as it fails to recover such stocks. This HCR needs to work in conjunction with a target, and several options have been tested. One area that needs further investigation is the use of the precautionary (PA) buffer, both its magnitude (which may differ depending on DLS category) and duration of application. The goal for the application of the PA buffer is to conserve stocks when there is uncer-tainty, hence its application should be related to the level of perceived risk. Information on the stock productivity and resilience can provide guidance on the duration of the period between PA buffer applications while guidance on acceptable range of PA buffer should be made by managers, taking into account the economic, biodiversity and ecosystem risks.
Stocks assigned to DLS Category 3 and Category 4 methods have a problem when SSB is declining and when a stock is overexploited. Category 3 methods are the most used this year by ICES in its advice but all the Category 3 HCRs tested lead to increasing biological risk over time and need a target to track movement towards MSY, as a pri-ority. New methods were explored, principally, survey-based methods based on the DATRAS database. Results are consistent for the examples explored. Catch-based methods (CMSY method) were explored further but the outstanding issue of which r-k to use remains an issue and further guidance is a priority. Size-based methods are being validated and all new methods could be applied systematically to all DLS to compare estimates of MSY proxies and then expertise used to reach consensus on ap-propriate values. However, for length-based methods it is necessary to identify avail-able data and any gaps for which further data collection is necessary before the methods can become operational.
Published under the auspices of the following ICES Steering Group or Committee