Norway lobster, Nephrops norvegicus (L.) was found to show diel activity patterns with more individuals outside their burrows at dawn and dusk in the Bay of Biscay in August 2004 and catchabilities were higher at these times. Using data from an onboard observer programme of Nephrops trawlers in 2002-2005, we investigated whether the expected variability in catchability was visible in commercial catches. Catch numbers per haul varied spatially and between months but no signal for diel variations was found. Fishing strategies developed by the Nephrops trawlers had several components. On a seasonal level they started around sunrise. On a haul level, haul duration decreased from haul to haul, with the longest hauls taking place at the time of highest catchability. The by-catch of hake, Merluccius merluccius (L.) increased more than proportionally with haul duration.