Milkfish (Chanos chanos) is one of the most preferred brackishwater food fishes in South-East Asian countries and India. It is an herbivore fish, tolerates wide range of salinities and accept low protein pellet feed under culture conditions. ICAR-CIBA achieved breakthrough in captive breeding of milkfish in outdoor RCC tank-based system. Open tanks are subjected to environmental variations which limits milkfish sexual maturation.
Hence, we have developed a 60 t RCC indoor recirculatory aquaculture system (RAS) where abiotic factors i.e. salinity, water temperature and photoperiod are controlled as per the requirement. RAS is also sheltered with temperature insulated panels which can withstand strong winds. RAS is equipped with rapid sand filters, protein skimmer, biofiltration module, ozone filter and egg collection unit. A separate water heating tank (7t) is attached with thermostatic titanium heaters (2kv each) and warm water further pumps into RAS to continuously maintain the required temperature. Fishes were PIT tagged and screened for VNN negative. Fourteen fishes of adult milkfish (Average BW 6.26 kg, Average TL 98 cm) were stocked (1.75 kg/t) in RAS as per sex ratio of M: F: 1:1 during April 2025 and salinity, temperature, and photoperiod was set at 33-34 ppt, 31-32 οC, 14L: 10 D respectively. Fishes were implanted with cholesterol pellets having hormone (GnRHa + 17 α Methyl Testosterone each 50μg/kg bw) and subjected to ultrasonographic scanning to monitor gonadal developments. Fishes were fed with institute’s milkfish broodplus feed for maturation. Environmentally controlled RAS system improved female maturation and milting male % compared to open tank-based system which exists parallelly Post biopsy oocyte growth was monitored microscopically and milt quality was assessed under computer assisted sperm analysis software (CASA). Functional brooders at an early age and smaller size developed in this RAS can be supplied to other hatcheries as milkfish takes long time (> 5 years) for sexual maturation in normal both captive and wild conditions. This system holds potential to form prospective brood bank of milkfish for year-round maturation in captivity and timely supply to hatcheries to jump-start the milkfish seed production.