1Nishinihon Institute of Technology, Nakamura Office, Nakamura, Kochi 787-0050, 2Usa Institute of Marine Biology, Kochi University, Tosa, Kochi 781-1164, Japan
The ayu Plecoglossus altivelis altivelis larvae were collected with an aqualamp (250W) from the Shimonokae estuary and the adjacent sandy beach in their three reproductive seasons (1st: December 1996-March 1997, 2nd: December 1997-March 1998, 3rd: December 1998-February 1999). Ayu were collected abundantly both in the estuary and sandy beach in the 1st and 2nd seasons. In the 3rd season, few ayu were collected from the sandy beach, although a large number of ayu were collected from the estuary. The daily precipitation in the 3rd hatching period (November-December) was less than that in the 1st and 2nd periods. These results suggest that the river discharge during the duration of downstream sweep of larvae influenced the dispersion of larvae to the sea.