Summaries of Presentations of Some Recent Method and Tool Developments:Advancing assessment methods for data-limited fish stocks

摘要

The assessment of data-limited fish stocks is crucial for the sustainable management of marine living resources. Dependent on the scope and type of available data, a range of assessment methods are available, such as catch only, length-based, or catchand survey-based methods. However, these methods suffer from several shortcomings, such as assuming equilibrium, over-simplifying biological processes and ecological interactions, and lacking quantification of assessment uncertainty. Here, we present several advancements of data-limited stock assessment methods tackling some of these limitations. The s6model (Kokkalis et ai, 2015; 2017) and updated traditional length-based assessment methods allow deriving biological reference levels from one year of length-frequency data while quantifying the assessment uncertainty. The stochastic production model in continuous time (SPiCT; Pedersen and Berg, 2017) requiring only catch and CPUE time series quantifies differences between seasonal patterns in the fishing mortality and productivity. The stage-based biomass dynamic model building upon SPiCT resolves biomass dynamics between the juvenile and adult stages, which improves the predictability of future biomass levels. The incorporation of stochastic data-limited methods into management strategy evaluation frameworks reveal appropriate harvest control rules for different stocks and how to account for the assessment uncertainty. The implementation and further development of such methods will contribute to a biological sustainable management of marine living resources, and provide robust platforms for additional quantitative economic analyses of the fisheries exploiting the resources.