NOAA scientists have been trialling active acoustics to see whether the method can be used to monitor snapper in the bottomfish fishing grounds off Hawaii.
Snappers live in subtropical and tropical oceans with rocky uneven bottoms. Modern research methods such as trawl sampling and underwater filming are not feasible in such terrain so researchers at the Pacific Islands Fisheries Science Center have conducted a study to see whether active acoustics can accurately determine abundance and biomass of the species.
Active acoustics emit a non-intrusive pulse of sound which echoes off objects. Different fish species product different signals depending on their size, orientation, gas-bladder characteristics and physiology.
“For these snappers the important echo characteristics are echo strength, individual swimming pattern, depth, distance from bottom, group density, number of fish in loose groups and shape of tight groups of fish,” said research oceanographer, Dr Réka Domokos.
These specific characteristics allow researchers to identify discrete species allowing for the snappers to be accurately monitored. Relative biomass and changes in the number of snapper over time can be determined, informing fishing practices and ensuing snapper fisheries are sustainable.