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To elucidate the recruitment and movement process of larval ayuin the surf zone of a sandy beach facing Tosa Bay, 31 collectionswere made with a small seine net at intervals of approximately 5days from November 1990 to April 1991. On the basis of seasonalvariations in larval abundance, size, age, duration of residence,and the occurrence patterns of ayu in the surf zone, larval ayuwere classified into two groups: short‐term resident (< 30days in duration) and long‐term resident (90–120 days).The former appeared in the surf zone abundantly from mid‐Novemberto mid‐December and resided there for about 1 month until they reachedapproximately 25 mm BL. It is likely that larval ayu (short‐termresident), which recruit abundantly to the surf zone, expand their distributionoffshore at approximately 25 mm BL. In contrast, the lattergroup were found after mid‐December, and the population size wasmarkedly small although they stayed continuously in the surf zonefor 3–4 months until they reached approximately 40 mmBL.

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To clarify the characteristics of the larval and juvenile fish community in a Japanese estuary, monthly collections were conducted in the shallow waters of the Shimanto Estuary, Japan from July 1985 to June 1987. A total of 49 101 fishes of more than 100 species from 44 families were sampled over the 2‐year period. Numerically, Gerres equulus was most common, accounting for 20.02% of the total abundance. Rhyncopelates oxyrhynchus was ranked second, followed by Acanthopagrus latus, Acanthogobius flavimanus, Mugil cephalus cephalus, Parioglossus dotui, and Acanthopagrus schlegeli. Thus, fishes observed in the estuary were mostly marine species that spawn in the sea. The majority of these fish first appeared within the estuary at late postlarval and/or early juvenile stages. Based on their utilization of the shallow waters in the estuary, the majority of species could be categorized as residents. In the Shimanto Estuary, shallow waters are studded with shelters, especially eelgrass beds, which serve as important nursery grounds for coastal and euryhaline fishes.