Japanese krill fishing operation was observed on board a commercial vessel and actual operation was described in detail. Fish finder was most useful in detecting swarms while sonar was used to judge the towing direction. Size of fished swarms ranged from 100 m to 10 km with different distribution in different fishing areas. While catch per towing time reflects within-swarm density catch per day was thought to be a good index to measure abundance of concentration. Comparison of such index across time and space may have difficulties in standardization when data from different vessels are to be used.
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