CONTINUOUS MONITORING OF FISH IN A SHALLOW CHANNEL USING A FIXED HORIZONTAL SONAR

An acoustic monitoring program of herring migration in Drogden channel, near Copenhagen, Denmark was conducted from June 1996 until the end of May 1997. Fixed 100-kHz side-looking sonars provided nearly continuous surveillance in a 1-km-wide by 12-m-deep navigation channel. Water temperature, salinity, and current profiles were simultaneously monitored at this site. The sonars were positioned to insonify regions near the seabed at ranges up to 800 m, such that the typical reverberation was due to low-grazing angle seabed backscatter. It was found that under normal, weakly stratified flow conditions, fish schools attributable to herring (Clupea harengus) were observed from the 50- to 500-m range. This could be done despite interference from the dense vessel traffic, specifically direct echoes from hulls, propeller cavitation noise, and bubbly wakes. At close ranges (<150 m) hyperbolic trajectories attributable to individual herring were observed, with horizontal advection speeds in close agreement with mea...

[1]  Abundance estimation of fish schools based on a relationship between school area and school biomass , 1993 .

[2]  J. Kubečka,et al.  Brown trout populations of three Scottish lochs estimated by horizontal sonar and multimesh gill nets , 1994 .

[3]  K. Foote.  Fish target strengths for use in echo integrator surveys , 1987 .

[4]  Roger P. Hewitt,et al.  DEVELOPMENT AND USE OF SONAR MAPPING FOR PELAGIC STOCK ASSESSMENT IN THE CALIFORNIA CURRENT AREA l , 1976 .

[5]  M. Trevorrow,et al.  Detection of Atlantic herring (Clupea harengus) schools in shallow waters using high-frequency sidescan sonars , 1998 .

[6]  M. Trevorrow,et al.  Detection of migrating salmon in the Fraser River using 100-kHz sidescan sonars , 1997 .

[7]  Ole Arve Misund,et al.  Mapping the shape, size, and density of fish schools by echo integration and a high-resolution sonar , 1995 .

[8]  A 5‐day long‐range sonar record of an extensive concentration of fish , 1989 .

[9]  K. G. Foote,et al.  A technique for calibration of monostatic echosounder systems , 1996 .

[10]  D. E. Weston,et al.  Fish echoes on a long-range sonar display , 1971 .

[11]  C. Clay,et al.  Acoustical Oceanography : Principles and Applications , 1977 .

[12]  M. L. Somers,et al.  An experimental survey of a herring fishery by long-range sonar , 1973 .

[13]  D. Farmer,et al.  Acoustical measurements of microbubbles within ship wakes , 1994 .

[14]  R. H. Love.  Target strength of an individual fish at any aspect , 1977 .