定置網の揚網間隔と漁獲量 Effects of Varied Hauling Intervals on Catch of a Set-net
In order to identify the relationship between the hauling interval and the catch quality and quantity of the small scale set-net, experimental operations was conducted in the fishing grouns of Tateyama Bay, Chiba prefecture in August, 1995. The experimental protocol of the bag net hauling procedure was designed to vary in different hauling intervals as 3hours (8hauls/day), 6hours (4hauls/day), 12hours (2hauls/day), and 24hours (1haul/day). The total of 75hauls for 5 series at 4 different intervals were made, so that the weigth of catch was recorded for all species. The average catch per haul was tended to increase in case of total catch for all species comprehensively, while the cumlative catch per day eventually decreased according to the prolonged hauling intervals. These results suggested that the average catch per haul can not be expected to increase in proportion with the hauling interval, because some species once trapped in the beg net were not always being cumulated, and escaped due to the time delay of hauling procedure. Catch cumulating according to the time period to the following haul can be also influenced by the time of day in relation to the rhythmic activity of each species. The percentage of fish remaining on the bag net to the next hauling could be estimated as only 1.7-40.2% at 6hours of the haulig interval for round herring <i>Etrumeus teres</i> that was dominant species on the experiment.
日本水産学会誌 63(3), 340-344, 1997-05-15