Working Group on Improving Use of Survey Data for Assessment and Advice (WGISDAA; outputs from 2024 meeting)

The Working Group on Improving Use of Survey Data for Assessment and Advice (WGISDAA) deals with various topics related to survey data such as experimental survey design, analysis of survey data, and its use in assessment models. The working group serves to bring together experts in data collection and statistical analysis and stock assessment in order to ensure the best possible science.

A common topic is the use of advanced statistical modelling tools for the analysis of survey data. Such tools can account for changes in survey design, combination of multiple surveys, dealing with highly skewed distributions, inclusion of environmental variables, quantification of uncertainty, and optimization of survey design. Comments and recommendations on how to proceed are provided by the group in each case.

Several topics related to analysis of survey data were touched upon during the meetings (2022-2024), ranging from specific case studies to more general modelling issues, summaries of recent ICES workshops relevant to the group, and planning of future workshops. The specific case studies included Northern Shelf Anglerfish, Rockall haddock, a predation index for Northern Shrimp, North Sea Turbot, and Baltic Plaice.

Important general recommendations are made regarding CPUE indices derived from the NS-IBTS surveys: Effort calculations should be based on the measured haul duration plus 5 minutes for Gadiformes and Pleuronectiformes to account for trawling at the bottom outside the nominal haul duration. For Clupeiformes effort should be assumed constant regardless of trawling time, because these swarm fishes are most often caught while deploying the net, or while hauling in. Haul duration works better as effort metric than swept area for all three orders of species.