Stock assessment of demersal fish in the ICES area generally relies on Virtual Population Analysis (VPA). The main data sets in this kind of analysis are derived from catch statistics and samples from commercial catches, that tend to be unreliable, as well as from scientific surveys.
The scientific trawls used to sample demersal fish are normally slightly modified commercial trawls that generally have a bad geometrical stability as well as important herding effects that tend to introduce additional bias in absolute and also relative density indices. The present proposal therefore aims at providing the strategy for designing a non-herding demersal survey trawl, primarily to provide representative samples, but ultimately to provide absolute density estimates.
Call for proposal