Report of the Workshop on Understanding and quantifying mortality in fish early-life stages (WKMOR)

Variable mortality of fish early-life stages and zooplankton can be a dominant factor controlling their overall dynamics and abundance in marine ecosystems. Developing methods to estimate and model mortality has received considerable attention in re-cent decades, but the subject remains one of key importance because it is difficult to adequately sample organisms, determine ages or stages, and assign causes to mortal-ity of planktonic animals in the sea. In addition, quantifying mortality is a critical component for understanding the factors that influence fisheries recruitment variabil-ity, including those due to climate variability and change. In this context, WKMOR was held to review and synthesize recent advances in modelling methodology and developments of new laboratory and field observational techniques to estimate and evaluate consequences of mortality. At the outset and during the workshop, it was clear that there has been considerable progress in quantifying mortality in the field (e.g., quantifying stage-specific abundances, estimating rates and causes or mortality, accounting for advection/diffusion effects) and for constructing process-based fore-casting tools (models) that quantitatively link spawning stock biomass/egg produc-tion with post-juvenile stages. It also is clear that mortality experienced by ichthyoplankton and zooplankton is neither constant in time, invariant in space, or predictable by body size and developmental stage alone.