LAUSR

Abstract Crossbreeding between wild and domesticated strains of important aquaculture species to determine potential for heterosis and heterobeltiosis is of interest to aquaculturists. The present study was aimed to evaluate broodstock strain effects and heterosis for growth and survival rates from larvae to grow out stages of bighead catfish (Clarias macrocephalus) crossed from one domesticated (Can Tho, CT) and two wild (Ca Mau, CM and Hau Giang, HG) populations. Nine crossbreeds were reared for 40 days at the larval stage in static tanks, 60 days for juveniles, and 90 days for grow out in recirculating systems. At harvest, pure CT exhibited the highest growth (final body weight BW = 154.1 ± 61.3 g), while HG × CT and HG × CM crossbreeds had the lowest (57.0 ± 17.0 g and 68.0 ± 28.5 g, respectively) and the other crossbreeds had intermediate values (mean BW ranged from 93.4 g to 113.1 g) (P = 0.01). The three stages showed consistently that the domestic CT strain grew faster than wild CM and HG strains. The growth performance of offspring was affected by dam strains, but not sire strains. Parental crosses generally had better growth rates compared to crossbreeds of the same dam source. However, crossbreeds did not differ in feed conversion ratios and survival rates from parental crosses. None of the crossbreeds had better growth than the better parent (heterobeltiosis), suggesting that crossbreeding among strains in the Mekong Delta may not be an effective genetic improvement program for bighead catfish.