Report of the Study Group on Survey Trawl Standardisation (SGSTS)

Bottom trawl surveys are the corner stone of marine fish resource surveying. They are used extensively in the monitoring and assessment of commercial species, and are often now used as the main or sole data for analytical assessments (Mesnil et al. 2009). They are now increasingly being used beyond the traditional single stock assessment role. In particular, they are being used to evaluate species assemblage makeup, and for production of indices of ecosystem health e.g. biodiversity or size spectra (Fraser et al. 2007, Nicholson and Jennings 2004, Piet and Jennings 2005). Most such surveys were not initially designed for these purposes, and it is increasingly important to un-derstand the performance of our sampling nets, and particularly to maintain that per-formance as consistently as possible.This report sets out to provide the state-of-the-art in the standardisation of survey bottom trawls and to provide guidance on how to maintain consistent and robust data sets from these gears for the many and often conflicting demands placed upon them.