Trial Observation of the Sound Scattering Layer Using an ROV.

Abstract

A remotely operated vehicle (ROV) was used to observe a sound scattering layer (SSL) identified using a quantitative echo sounder near the mouth of Funka Bay, Hokkaido. The SSL was seen in a high frequency (100kHz) echogram to occur within 5 m of the sea floor. Video images taken by the ROV showed a dense school of krill swimming rapidly and continuously within the SSL. Furthermore, several walleye pollock were observed to approach the ROV at depths where relatively strong echoes appeared in a low frequency (25kHz) echogram. The density and size of the krill and walleye pollock were not determined, however, it is clear that ROVs are useful for observing the SSL and can provide valuable information about the biomass of marine resources more accurately.