Combined underwater acoustic and radar instruments for assessing fish near seabed and mapping seabed

An underwater acoustic and marine radar survey was conducted for the assessment of fish near the seabed and for seabed mapping. For the purpose, an underwater acoustic instrument (split beam echo sounder), and ground penetrating radar (GPR) were used around Seribu Island, Jakarta Bay. Research vessel Mina Jaya (30 GT) and various marine research instruments were employed during the survey. The results show that the fish density near seabed is 0.3 to 35.0 fish/1000 m/sup 3/ with fish length up to 44.6 cm. Radar has a higher resolution for subbottom detection than high frequency acoustics.