Breeding in captivity for conservation and livelihood: insights into the early ontogeny of the Indigo barb, Pethia setnai (Chhapgar and Sane 1992), a threatened endemic species of the Western Ghats of India

The study provides the first comprehensive account of the developmental biology of the Indigo barb in captivity. The males develop a reddish hue on the body and margins of their median fins, as opposed to the dull coloration of the females. The fish spawned 6–7 h after administering the breeding hormone, and the fertilized eggs were demersal and adhesive. The larvae hatched 22 h ± 20 min post-fertilization and were demersal with distinctive crawling movements. The yolk sac larvae were 2.48 ± 0.032 mm in total length, with a non-pigmented body and pear-shaped yolk sac. The pre-flexion stage was attained 4 days after hatching, with a single-chambered swim bladder and melanophore aggregation along the body. The larvae reached the flexion stage on day 16, with a body length of 4.54 ± 0.36 mm and the development of caudal fin rays. On the 28th day, the post-flexion stage had produced all of the fins except the pelvics, a two-chambered swim bladder, and a distinctive sub-dorsal blotch. The presence of a supra-anal band and the emergence of scales over the caudal area characterized the juvenile stage. The baseline information on early ontogeny will be valuable for the conservation and sustainable use of the species.