(2) Development of acoustic survey for mid- and deep-sea fish biomass
Acoustic technique enables us to estimate size and number of fish by supersonic waves. Analytical methods as well as acoustic techniques and devices are now being developed to identify mid- and deep-sea fish and to estimate biomass of them. Recently, the results of acoustic surveys were combined with those of quantitative net samplings of fish, which revealed the existence of prey-predator interactions between small pelagic fish (e.g. sardine and mackerel) and mid- and deep-sea fish (e.g. myctophid fish) off Doto and Sanriku areas.
Echogram obtained in the subarctic region (left) and schematic diagram of the prey?predator relationships among mid- and deep-sea fish and small pelagic fish.
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