Seedling production of the short barbeled velvetchin, Hapalogenys nigripinnis (Temminck and Schlegel, 1843) with special reference to the early stage morphology
2020
Kita, J. ((Demonstration Laboratory, Marine Ecology Research Institute, Kashiwazaki, Niigata (Japan)), (Central Laboratory, Marine Ecology Research Institute, Chiba (Japan))) | Watanabe, Y. | Shionoya, M. | Kojima, J.
We experimented with seedling production of Hapalogenys nigripinnis, using broodstock caught off Kashiwazaki, Niigata. At 31 days after hatching, 2,760 juveniles (c.a. 17 mm in standard length) could be produced in 500 l black polycarbonate tanks. The number of dead individuals increased at 8 days after hatching, which was thought to be due to the stampede swimming of the larvae responding to sudden changes in the light condition. Feeding regimes of early stages was to feed freshly spawned eggs of Sillago japonica after L-type rotifer feeding. It was thought that the feeding regime should be reexamined because of their weak preference for live eggs. Seawater temperatures of about 9℃ and 29℃ were continued for one month during the acclimatization period of broodstock, but the fish grew well without any weakening of feeding. They can be said to be resistant to high and low water temperatures. It is noted that they have a high resistance to abrasions. The spawning optimum temperature range is estimated to be between 23℃ and 26℃. Maturation and spawning rhythms are estimated to be asynchronous type and to have multiple spawning. The early life morphology of cultured specimen is detailed in comparison with previous findings.
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