Larval development of Odontobutis obscura obscura, reared with Artemia sp.and Limnodrilus sp.for about two months, was observed in a room maintained at 20±0.5°C. The development was classified into nine nominal stages, and was compared with that of O. o. interrupta and of O. platycephala. The size and shape of the eggs and the development of this species are similar to those of O. o. interrupta and O. platycephala. From the juvenile stage, O. obscura is distinguishable from O. platycephala by the appearance of dark bands on the body located in the same position as in adults. O. o. interrupta is also distinguished from O. o. obscura in the juvenile stage by the presence of melanophores on the dorsal and ventral sides of the caudal peduncle. The anal fin fold of O. obscura is higher than the dorsal fin fold, but the two folds are equal in height in O. platycephala. O. obscura has a well-developed air bladder and swims high in the water at the feeding stage. O. platycephala has a poorly developed air bladder and swims on the bottom. Xanthophores are observed at an earlier stage and more strongly developed in O. obscura than in O. platycephala. Growth rate is faster in O. obscura than in O. platycephala. O. obscura spawns at a smaller body size than O. platycephala. In O. o. obscura, the arrangement of cephalic pit organs is completed at 14mm SL. In O. o. interrupta, this arrangement is completed at the same time or a little later than in O. o. obscura. The infraorbital and verticalantorbital pit lines of O. platycephala, which are separated in the adults, are connected until the juveniles measure about 30mm SL. These pit lines are connected even in the adults of O. o. obscura and interrupta. In O. platycephala, the sensory canals are first formed behind the eyes, then dorso-anterior to the eyes, then at the posterior edge of the preopercles and finally anterior to the eyes. Postocular canals begin to form in individuals more than 20mm SL. All individuals of O. o. interrupta more than 70mm SL have postocular canals. O. o. obscura has no sensory canals throughout life. The differences in growth rate, body size at spawning, and the time of completion of the cephalic lateral line system suggest paedomorphosis in the three taxa studied here.
A total of 7, 000 larval and juvenile Plecoglossus altivelis was collected at semimonthly intervals with a small seine in a surf zone of Tei beach facing Tosa Bay during the period of June 1982 to May 1983. They occurred in the surf zone from middle October to middle May. About 500 larvae and juveniles (10.9-59.9 mm TL) were used to examine their feeding habit. The feeding incidences by collection dates fluctuated from 0 to 100%, with 90.6% in total incidence. They fed mainly on copepods (e.g. Paracalanus parvus and Oithona spp.) throughout postlarval and juvenile stages, while they first took small benthic animals at 53.0mm TL. Their food compositions were influenced fundamentally by the planktonic fauna of the surf zone, but larvae under 20mm TL tended to take relatively larger copepods.