Some Biological Aspects of Local and Thai Koi,Anabas Testudineus (Bloch), Their Artificial Hybridization and Evidence of Natural Hybridization

Abstract

The different strains of the climbing perch, Anabas testudineus are found in different countries. Being different in origin, Thai koi possesses some biological differences from the native koi of Bangladesh. A comparative study of some biological aspects was carried out from July to December, 2008. All the fishes were reared and collected from Batiaghata, Khulna. The total length and body weight of Thai koi broods were higher than that of the local koi broods with a significant difference (p<0.05). The length-weight relationship of both strains was positive with r=0.95 and 0.76 for Thai and local respectively. The fecundity of Thai koi found 765245±105027 after PG hormone administration (8 mg kg⁻¹) was higher than that of local koi (345508±114502). Managing by the supplementary feed, a high GSI was found in both Thai and local koi over three months period having higher value in Thai than that in the local females. Three nutritional compositions (moisture, protein and lipid) were not significantly different between the Thai and local koi muscle; however, a little higher value was found in the local koi than Thai ones. The juvenile of local koi surfaced out for air gulping more frequently than that of Thai koi (p<0.05) though the adult of the two strains did not show any significant difference (p>0.05). From most of the morphometric, meristic and qualitative characteristics the local koi varied from the Thai koi. In case of artificial hybridization pure local and Thai produced more fertilization and hatching rates than the reciprocal cross-breds though the survival rate of hybrids in cisterns was higher than the two single strains. During checking out the natural hybridization of koi in local beels, the incidence of escaping of Thai koi from culture ponds was found and average 17.40% of the beel catches were found with Thai and/or putative hybrids with body spots; among the sampled spotted koi, 66.7% were identified as hybrids based on morphometric, meristic and qualitative characters.