2.3. An experiment on strain crossing of African catfish
2.3.1. The strains used and the artificial breeding
Two African catfish populations, from Angthong (AT) and Nakornpathom (NP) provinces, were selected for the crossbreeding experiment based on their genetic distinctness and the availability of the gravid brooders. Four crosses were performed using a total of eighteen brooders (1:1 male:female) each from the AT and NP populations. The gravid female brooders were injected with 30 μg/kg buserellin acetate (LHRHa) (Suprefact) and 5 mg/kg dopamine antagonist (motilium), while 10 μg/kg buserellin acetate and the same amount of dopamine antagonistwere injected into male brooders. At 10–12 h after the injections, the eggs fromeach femalewere stripped, separated into two portions and each portionwas fertilized with sperm solution squeezed fromthe ground testes of either a male fromthe same strain or the others. The fertilized eggs from each full-sib family were incubated in a hatching bowl equipped with a water flow-through system. Hatching commenced at about 24 h after fertilization and then the fry belonged to the same cross-typewere pooled and the cross-types were named as follow, ATxAT, NPxNP, ATxNP (female AT mated with male NP) and NPxAT (female NP mated with male AT).