RV Corella Fisheries Laboratory cooperated with the Admiralty Research Laboratory to identify fish detected by long-range sonar equipment installed at the Admiralty Experimental Station, Perranporth. The RV "Corella" was directed from the shore to an area some 65 km distant, that was returning a strong and extended echo. The "Corella" was able to correlate this target with shoals detected on a conventional echo sounder, and substantial catches of sprats were taken in the area using a midwater trawl. The RV "Corella" was used throughout the 1970s for pioneering studies on fish migration. Individual plaice ("Pleuronectes platessa") fitted with 300 kHz acoustic transponding
Anyperodon than the upper jaw. There are no palatine teeth, a fact which distinguishes this species from other groupers. The basic colour is pale reddish-brown liberally dotted with orange spots which are closer together on the head. There are five pale silvery blue longitudinal lines running down either side, the lower 3 reaching the tail but the upper two breaking into irregular streaks. The dorsal fin has 11 spines and 14 to 16 soft rays. The anal fin has 3 spines and 8 to 9 soft rays. Juvenile fish have vivid blue and red longitudinal stripes. The slender grouper has a