Resumen:
The normal behavioral patterns of several fish species is altered during trawling affecting the fish spatial distribution. Sonar methods were carried out in this research work in order to study the reaction of reproductive concentrations of the Argentine hake (Merluccius hubbsi) during mid-water and bottom fishing trawls. Observations made from a trawl sonar mounted on the headrope of an ENGEL (35 m) bottom trawl, showed that this species concentrates at the lower-central sector of the net mouth. During daytime trawls fish schools with a vertical distribution exceeding ten meters were observed entering the trawl within the first two meters from the bottom. Some observations during pelagic trawls carried out at night, showed no specific pattern at the net mouth. The observational method was efficient when fish densities were higher than 66,662 fish per nautical mile2, although it may only be considered as representative of the survey conditions, that is to say summer spawning concentrations of Argentine hake.
