Direct assessment of small pelagic fish by the PELGAS17 acoustic survey
|Ref.||Working Document for WGHANSA (Bilbao, 24-29 June.2017)|
|Author(s)||Duhamel Erwan1, Doray Mathieu2, Huret Martin1, Sanchez Florence5, Lespagnol Patrick1, Doremus Gislain4, Le Bourdonnec Pierre3|
|Affiliation(s)||1 : IFREMER, lab. Fisheries Research, 8 rue François Toullec 56100 LORIENT, France
2 : IFREMER, lab. Fisheries Ecology, BP 21105, F- 44311, Nantes, France
3 : CNPMEM, 134 avenue de Malakoff, 75116 PARIS, France
4 : Observatoire PELAGIS - UMS 3462 - Université de La Rochelle – CNRS - Pôle Analytique – 5 allée de l’Océan - 17000 LA ROCHELLE, France
5 : IFREMER, Allée du Parc Montaury 64600 Anglet, France
An acoustic survey (PELGAS) is carried out every year in the Bay of Biscay in spring onboard the French research vessel Thalassa. The objective of PELGAS survey is to study the abundance and distribution of pelagic fish in the Bay of Biscay. The main target species are anchovy and sardine but they are considered in a multi-specific context and within an ecosystemic approach as they are located in the centre of pelagic ecosystem.
The Pelgas17 acoustic survey has been carried out with medium weather conditions (regular wind, low atmospheric 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 110 valid identification hauls instead of about 60 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. Vessels (and the scientific observer onboard) are founded by EMFF (European Maritime and Ficheries Found) for the period 2017- 2019, with the financial help of "France Filière Pêche" which is a groupment of French fishing organisations.
The PELGAS17 survey observed a relatively high level of anchovy biomass (134 500 tons), which seems to be higher to previous year, comparable to 2011 and far away from the 2015 biomass
The biomass estimate of sardine observed is 465 022 tons, which constitutes a strong increase from the last survey.