1Faculty of Fisheries, Nagasaki University, Nagasaki 852-8521, 2Department of Fisheries, Kinki University, Nara 631-8505, Japan
The catch of Sepia esculenta in Shimabara Sound may be affected by the tidal current conditions in the fishing ground. In order to collect basic data on catch variations of S. esculenta, the effect of tidal current conditions on catches of the pot fishery was investigated. The daily catch data analyzed were obtained with cuttlefish basket traps during the 1997 fishing season (20 February-28 May 1997). The tidal current was recorded over a 25-day period (22 April-22 May 1997) continuously using a current meter set at the depth 20cm above the bottom at 10-minute intervals. The tidal current conditions changed periodically with the lunar fortnightly. Current velocity increased at spring tide and decreased at neap tide. Daily catch variations were closely related to the age of the moon, with the catch increasing at neap tide, and decreasing at spring tide. Tidal current is, therefore, one of important physical environmental factors that affects the entry behavior of S. esculenta toward a basket trap in a fishing ground.