Nutrition-sensitive approaches to aquaculture promote the production of micronutrient-rich small indigenous species (SIS) such as mola Amblypharyngodon mola, which is particularly rich in essential micronutrients, including vitamins A and B12, calcium and zinc, to address malnutrition in the developing world. However, to date, a lack of standardized hatchery-based mass production techniques for SIS seed has proven a key technical barrier to realizing the full potential of nutrition-sensitive aquaculture. To address this crucial bottleneck, WorldFish is implementing a project titled "Taking nutrition-sensitive carp-SIS polyculture technology to scale" in the Indian states of Assam and Odisha with funding from GIZ. A key goal of the project is to develop scalable mass production techniques for A. mola seed, based on a standardized protocol for hatchery-based breeding.
During breeding trials in Odisha, India, mola broodstock were collected from multiple sources to ensure genetic diversity and conditioned in broodstock ponds for two months at a partner hatchery (Lat 20°12’45.84"N/Long 86°20’3.32"E). Brooders were fed to satiation with 42% CP floating extruded feed twice daily. Six breeding experiments were conducted during peak breeding season (June–August 2022), with a natural photoperiod (12:12). Selected breeders were identified based on secondary sexual characteristics and transferred to a concrete conditioning tank (capacity: 10 m3) with constant water flow for stimulating spawning readiness. A combination of hormone administration and environmental manipulation was used to increase seed production. Synthetic GnRH-based inducing hormone was administered through the peritoneal cavity of mola brood (mean body weight 8.0 ± 0.55 for females and 3.75 ± 0.81 g for males, with a 1: 2 sex ratio) between 16–20.5 h, at the rate of 0.5 ml kg–1 body weight for females and 0.25 ml kg-1 for males. The fish were returned to double hapas inside breeding tanks and exposed to a constant shower of oxygen-rich water from an overhead tank equipped with an aeration tower. At water temperatures of 28-29.5°C, the latency periods were observed as between 6–8 h, when male brooders began chasing the females within 6-8 hours of hormone administration. Each male was found to be actively and aggressively paired with a single female, while eggs were released and fertilized by the male. The released eggs were collected in 250 micron mesh outer hapa and became slightly adhesive following fertilization. The breeding activity was repeated several times. Hatching of larvae was observed after 12 h of fertilization at 28-29.5°C water temperature. Average performance values from the six breeding cycles are depicted in Table 1. The fertilization, hatching, and survival rates were 89%, 91% and 92% respectively (Table 1). Hatchling production was significantly correlated with female body weight (r= 0.82; P≤0.05). Average production over 6 breeding cycles was 0.28 million hatchlings kg-1 of female mola brood. Average physico-chemical parameters during the trials were: air temperature 32 °C, water temperature 28.75°C, pH 7.6, dissolved oxygen 7.2 ppm, and alkalinity 116.25 ppm. The six breeding trials produced a total 5.48 million mola hatchlings. Mola hatchlings were ready for sale after 3-4 days and 2.13 million hatchlings and 37000 fry (21 days old) were purchased by 15 local farmers. This ground-breaking commercial mass seed production trial with mola will facilitate large-scale adoption of carp-SIS polyculture to increase farm incomes and consumption of micronutrient-dense fish in regions of India where undernutrition is prevalent.