These data contain biological information (length, weight, age) on samples of Maurolicus muelleri and other species (bycatch) collected respectively during R/V Bjarni Sæmundsson cruise B3-2010 southwest of Iceland (period 2010-01-26/2010-02-04) and from catches in experimental and commercial pearlside fishery in 2009-2011. Fishery vessels IDs are randomized except for Bjarni Sæmundsson (vessel_id 1131). The randomized IDs are the same as in the associated files (Maurolicus_muelleri NASC value survey B3-2010 and Experimental fisheries catches) distributed along with this data set. Trawl specification (mostly modified capelin trawls) such as horizontal and vertical openings, tow depth, tow length, sweep length and mesh size were recorded. Standard weather conditions are also mentioned (wind speed and direction, cloud cover and sea state).