WWW.WAS.ORG • WORLD AQUACULTURE • MARCH 2026 27 brooder tanks is maintained at optimum levels by exchanging 20-30% of the water every fortnight. Sexual Dimorphism Male H. nigricollaris typically exhibit darker pigmentation, more pronounced collar markings, and a slimmer body profile compared to females. Females exhibited a distinctive light red marking around their vent, absent in males, and possess a gently swollen abdomen. Maturity in males was indicated by the effortless release of white milt upon gentle pressure on the belly, while females released uniformly sized, golden-yellow color eggs. Maturity In captivity, H. nigricollaris exhibited gonadal maturation, with individuals weighing over 50 to 60 g reaching sexual maturity. The breeding season for H. nigricollaris extends from November to February during the pre-monsoon season. Field observations indicate that the species likely deposits its eggs in protected areas of the river bed, such as under rocks or within crevices. These unique reproductive traits make H. nigricollaris an excellent candidate species for targeted captive breeding programs. A sex ratio of 1:1 (male to female) is recommended for the successful breeding of H. nigricollaris (Figure 2). H. nigricollaris reaches sexual maturity at 1+ year and adult fish, 2-3 years old, are considered ideal for induced breeding. Brood fish are identified based on secondary sexual characteristics. Selected brooders are segregated by sex and housed in indoor tanks equipped with mild aeration and water showers to prepare them for induced breeding. Induced Breeding H. nigricolaris brooders with an average body weight of 50 to 100 g and an average length of 17 to 20 cm were used in this study. Induced breeding was carried out during the ideal season. Sexually matured males and females of almost similar size were selected for breeding at a sex ratio of 1:1. Artificial breeding was carried out using WOVA-FH (sGnRHa + domperidone) (Biostadt, India). Both males and females were administered 1 ml/kg body weight (Abhilash et al., 2025). After 12-13 hours, ovulated eggs were observed on a rubber mat at the bottom of the tank and on spawning mops. Incubation and Hatching After 12 hours, the eggs attached to the mops were carefully collected and placed into a plastic tub. After transferring the brooders, the rubber mat from the breeding tank was also moved to another incubation tank. Fertilized eggs were spherical, adhesive, and golden yellow in color. During incubation, as the embryos developed, the fertilized eggs darkened. Hatching occurred within 24 to 30 hours, depending on temperature. Larval Rearing Larval rearing is one of the most challenging aspects in H. nigricollaris. Newly hatched larvae measure about 4-5 mm in length and are extremely sensitive to environmental changes. They are initially housed in 50-liter rearing tubs with constant aeration. Feeding begins three days post hatching, with live Artemia naupli being offered four times daily. This stage is critical, as insufficient feeding or poor water quality can lead to high mortality. Five days (CONTINUED ON PAGE 28) FIGURE 3. 30 Dph larvae of H. nigricollaris, photographed by the first author. FIGURE 4. H. nigricollaris 3 months old fingerlings, photographed by the fourth author. As awareness grows regarding the ecological importance and ornamental value of H. nigricollaris, ongoing efforts aim to develop effective breeding techniques and promote responsible aquaculture practices. This approach not only seeks to replenish natural populations, but also supports local economies dependent on this unique catfish species.
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