In situ acoustic target strength of juvenile capelin

A dispersed, monospecific aggregation of juvenile (0+) capelin was detected acoustically in shallow (20-70 m) water in Bonavista Bay, northeastern New foundland in January 2000. This provided a rare opportunity to measure acou stic target strength (TS) of very small (mean length=51 mm) capelin in situ . Mean observed TS at 38 kHz was - 61.0 dB. Observed TS was similar to TS p redicted by the Norwegian-Icelandic capelin TS-length relationship (TS=19.1 log L (cm)- 74). but similar to2 dB lower than predicted by the existing T S-length relationship for capelin in Newfoundland waters at 38 and 49 kHz ( TS=20 log L (cm)-73.1). Combining present data with previous 38 kHz data in dicates the relationship TS=23.3 log L (cm)-77.1 (r(2)=0.95, n=6) for capel in of lengths 5-14 cm in Newfoundland waters. (C) 2001 International Counci l for the Exploration of the Sea.