GOMUT UNSRISONG1, PRASAN PORNSOPIN1, SOMPORN KANTIYAWONG1, BORIS DE LAPEYRE2, STEPHAN WESSELS2, GABRIELE HÖRSTGEN-SCHWARK2
1Chiang Mai Inland Fisheries Research and Development Centre, Department of Fisheries, Thailand
2Georg-August-University Göttingen, Institute of Animal Husbandry and Genetics, Germany
The batfish belongs to the family Sisoridae (Sisorid catfishes) and is native to the Mekong and Chao Phyraya basins. The species inhabits high mountain streams and feeds on insects and worms. In northern Thailand, the fish was found abundantly in the streams of the mountain area of Doi Inthanon and Doi Chiang Dow, where they hide under the rocks, but nowadays the numbers are decreasing substantially. A restocking programme is planned, however, till now no information is available about artificial reproduction of this species. Therefore 92 fish with an average size of 8.4cm and an average weight of 5.5 g were collected from streams of the Chiang Dow district in Chiang Mai province. These streams are characterised by a mean water temperature of 18C, dissolved oxygen of 7 to 11 mg l-1, pH 6.4 to 8.9, water hardness of 19 mg l-1 as CaCO3, and 2.24 mg l-1 free CO2. The fish were transported to the Chiang Mai Inland Fisheries Research and Development Center, Department of Fisheries, Chiang Mai, where the fish were kept in aquaria. Male and females could be distinguished clearly only in the spawning season which occurred from February to October. The sex ratio of fish was 1:1.18 male to female. In March, fish were injected with burselin acetate (305#5g kg-1 body weight) and domperidone (10 mg kg-1 body weight) to induce spawning. Brood fish started spawning 24 hours after injection. Stripped eggs were yellow, of round shape and 0.35cm in nucleus diameter. The incubation period of fertilised eggs was around 240 hours at 18-20C water temperature with a mean hatching rate of 15%. Newly hatched fry had a total length of 1.05-1.20cm and a yolk sac diameter of 0.35cm. The post larval period was 28 days with fry size of 2.1cm length and 0.065 g weight.
Keywords: Aquaculture, induced spawning, Oreoglanis siamensis