Direct assessment of small pelagic fish by the PELGAS15 acoustic survey

Abstract

The Pelgas15 acoustic survey has been carried out with globally good weather conditions (regular low wind, medium temperatures) for the whole area, from the South of the bay of Biscay to the west of Brittany. The help of commercial vessels (two pairs of pelagic trawlers and a single one) during 18 days provided about 130 valid identification hauls instead of about 50 before 2007 when Thalassa was alone to identify echotraces. Their participation increased the precision of identification of echoes and some double hauls permitted to confirm that results provided by the two types of vessels (R/V and Fishing boats) were comparable and usable for biomass estimate purposes. These commercial vessels participated to the PELGAS survey in a very good spirit of collaboration, with the financial help of "France Filière Pêche" which is a groupment of French fishing organisations. The PELGAS15 survey observed the highest level of anchovy biomass never observed before (372 916 tons), pushed by a huge recruitment (the abundance of age 1 in 2015 is more or less 4 times the highest before) far from the highest level observed on the time series (186 865 tons in 2012). In the South, anchovy was mostly concentrated in the middle of the platform, and in the middle part of the bay of Biscay, anchovy appeared as very small fish with highest concentrations front of the Gironde, never observed before. In this area, anchovy was present from the coast until the shelf break continuously