Target-strength measurements of Pacific hake (Merluccius productus) in Canadian waters using quasi-ideal and conventional beam transducers

Abstract

A joint Japanese/Canadian research cruise was carried out during May and June 1994 off the west coast of Canada to obtain two independent estimates of the in situ target strength (TS) of Pacific hake (Merluccius productus). Two vessels with independent quantitative echosounder systems were used. One was equipped with 120 and 50 kHz transducers, while the other used 38 kHz. The 120 kHz transducer featured a quasi-ideal beam pattern with a relatively flat response near the beam axis and low side lobes. Different single-beam TS estimation procedures were used to estimate TS from either system. Fish targets were identified by midwater trawling on the same or the next day. On one occasion both vessels were used to fish and measure TS simultaneously. The observed mean night-time TS for adult hake ranged from -36.4 to -30.4 dB kg-1. © 1996 International Council for the Exploration of the Sea.