FN Archimer Export Format
PT AVIS
TI Reliability of species identification from mid-water trawl catches during acoustic surveys : a catchability study
BT 
AF MASSE, Jacques
   GUIHO, Nicolas
AS 1:1;2:1;
FF 1:;2:PDG-DOP-DCN-EMH;
C1 IFREMER, DRV/RH/ECOHAL rue de l'Ile d'Yeu, B.P. 1105, 44311 Nantes cedex 03, FRANCE
C2 IFREMER, FRANCE
SI NANTES
SE PDG-DOP-DCN-EMH
UR https://archimer.ifremer.fr/doc/00203/31438/29834.pdf
LA English
DT Expertises
CR DAAG 91
   DAAG 92
   ERAG 93
   ERAG 94
BO Thalassa
AB Objective echoes identification is not possible nowadays when several species are present in an area. Mid-water trawl catches are usually used to split fish schools into species during acoustic surveys. Moreover it is weIl known that because of a lively behaviour of these types of species, the catchability may vary a lot from one species to another. Therefore, in order to verify the reliability of identification by trawling, 68 hauls carried out during 4 acoustic surveys (1991-1994) have been analysed. Five pelagic species (anchovy, mackerel, horse-mackerel, sprat and sardine), observed during these surveys in Bay of Biscay were considered. On the one hand, taking into account the vertical echo-sounder data and the vertical course of the trawl from nets onde data, a theoretical weight was calculated, and compared with the real catch. The results showed that catchability varied a lot between species and within species according to school structure. On the other hand, a vertical avoidance of fish was simulated by changing the vertical trawl position to approach the real catch and study specific behaviours which could bias the identification. As a result, it seems that trawl species compositions could be used with a better precision by applying a correcting factor according to specific catchabilities if completed by an aggregation classification.
PY 1996
ID 31438
ER

EF