The genetic basis and expression patterns of key genes are important aspects of study to understand the colouration. This trait differs between wild and domesticated fish which is a matter of research. Botia dario is an indigenous fish, having ornamental and aesthetic value, which shows faded appearance in terms of colour in domesticated condition than wild. In the present study the carotenoid-fed B. dario were examined through incorporation of marigold petal meal in the diets at the rate of 5, 10 and 15% w/w along with wild fish. The carotenoid content of tissues that is skin, muscle and intestine along with intensity of colouration increased in a dose dependant manner of carotenoid in the diet. Important carotenoid-based colouration genes that is csf1r, BCDO2, SR-B1, MLN64, STAR5, GSTA2 and PLIN2 were characterized in the fish, to find out their role in fish pigmentation. The significant difference (p < 0.05) in the expression of these genes in different tissues, when compared among carotenoid-fed domesticated and wild fish, revealed the mechanism responsible for faded colouration and also revealed the means to enhance colour in the fish.

An experiment was conducted to breed a near threatened Cyprinid Osteobrama belangeri in captivity through hormonal inducement. Carp pituitary extract (CPE) and three different GnRH based synthetic hormones viz., Ovaprim, Ovatide and Wova-FH were used as inducing agents. Experiment was conducted following a Completely Randomized Design (CRD). The brooders were injected with different doses of hormones and kept in the breeding hapas at 2:1 male to female ratio. All the inducing agents induced the fishes to breed, whereas no breeding was observed in the control set. Spawning success rate varied depending on the rate of inducement and the type of inducing agent used. CPE at a dose of 9mgkg−1 of female and 3mgkg−1 of male as well as the synthetic hormones at 0.5mlkg−1 of female and 0.2mlkg−1 of male brooders were found to be effective in inducing the fishes to breed in captivity. Efficacy of the synthetic hormones was significantly higher than that of CPE (P<0.05). Dose of hormone apparently affected the percentage of fertilization, egg output, hatching rate and spawn production. Administering an over-dose of the inducing agents caused early milting resulting in poor fertilization and under-dosing might cause late inducement in males. The present breeding protocol is simple and can be taken up by small breeders. It will be helpful in aquaculture and conservation of O. belangeri