著者

森内 新二 道津 喜衛

出版者

長崎大学水産学部

雑誌

長崎大学水産学部研究報告 = Bulletin of the Faculty of Fisheries, Nagasaki University (ISSN:05471427)

巻号頁・発行日

vol.36, pp.7-12, 1973-12

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Natural egg masses of the sea catfish, Plotosus anguillaris (Lacpede) were collected from the shore of Nomo Bay in Nomosaki (Lat. 32° 35.3' N, Long. 129° 45.5' E). The first egg mass was collected on June 12, 1972. The second and third collections were made on June 2 and July 1, 1973 respectively. The egg masses of the sea catfish were found in the shallow tide pool on the muddy shore during the ebb tide, being deposited in small holes under a vinyl sheet or cement boards probably made by the spawners, and being usually guarded by males. The eggs were spherical in shape measuring from 3.12mm. to 3.50mm. in diameter, non-adhesive and demersal. The egg yolk was considerably large and bright yellow in colour. The rearing and handling of eggs were found very difficult despite the size of egg and hence it was thought indispensable to have the knowledge of incubating habit of the male parent in order to be successful in normal development and hatching of eggs. Hatching was successful only from one egg mass collected on July 1, 1973 which was fortunately fully developed after the eggs were kept in the aquarium for only four days while the other two egg masses still at the early developmental stages were absolutely unsuccessful. The newly hatched out prolarvae, about 6.9 mm. in the total length, could not move to the water surface because of the big yolks and remained at the bottom of the aquarium. It took about 10 days before completing the yolk absorption and attaining the free swimming stage. About 4 days after hatching, the prolarvae began to move crawling along the bottom of the aquarium and gathered themselves at a certain area, showing their instinct of schooling. The rudiment of dendritic appendage of the urogenital papilla appeared already in the newly hatched larvae and it developed into a complicated form in the course of larval development. The postlarvae at the early swimming life stage measuring about 15 mm. in total length, already showed the appearance resembling the adult. From the free swimming stage, the larvae were bred for one month with nauplii of brine shrimp, Artemia salina.