Research Document 1996/067
Intercalibration of eight otter-trawlers participating in the sentinel fisheries in the northern Gulf of St. Lawrence (3Pn,4RS) in 1995 through the use of SCANMAR sensors
By A. Fréchet
The use of multiple vessels to perform a stratified random groundfish survey presents a difficulty given that the trawls may not have the same geometry. The geometry of a standard otter trawl may vary from one boat to another because of unique properties of each boat. We have tried to reduce this inter-boat variability by forcing the use of a single type of otter trawl. In order to verify the geometry of the trawls in a fishing situation, trials were done using SCANMAR acoustic sensors.
We found that the wing-spread varied from one boat to the next, the range could reach 20%. Coefficients were derived in order to compare the fishing power of each boat. The average catches are thus calculated with a standard of 19 meters for the whole fleet. It was recommended to control gear geometry with the use of a restraining cable instead of adjusting the catch using parameters derived for wing-spread because in fact, it is the catchability of the whole gear that reacts with changes in wing spread.
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