Abstract
To clarify the early life history of a fluviatile goby (“Kibara-yoshinobori”) Rhinogobius sp.YB, the morphological characters of newly hatched larva and distribution pattern of larvae were investigated, while collecting the eggs and drifting larvae from March 2000 to April 2002 at four stations in the upper stream of Sumiyo River, Amami-oshima Island, southern Japan. Judging from the appearance of clutch of eggs and larvae, the breeding period was assumed to last for three months from April to June with a peak in May. The egg diameter was larger than that from Okinawa-jima Island and any other waters of Amami-oshima Island. Thelar gest embryos collected from egg clutch showed a postflexion stage, forming second dorsal, anal and principal caudal fin rays. These characters denoted a more advanced stage than previously reported. The larvae gathered in the shallow water area (<40 cm) with low current velocity (<5 cm/s) near shore and around substratum. The swimming ability of the newly hatched larvae and characteristic distribution of the larvae reduced a carry-away risk and thus enabled their life history within stream.
