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The aim of the present study was to design and operate a recirculation aquaculture system (RAS) for the production of rotifers Brachionus calyciflorus, with recognition of preferred food type and effective harvest rate. In experiment 1, four food types (Chlorella vulgaris, Spirulina major, Scenedesmus obliquus, and baker's yeast) were used to determine the food type that was preferred by the rotifers. Chlorella vulgaris was the most preferred food type based on the highest rotifer count (365.33 ± 2.18 rotifers/mL). In experiment 2, rotifers were harvested at 10, 30, 50, and 70% of the total volume on a daily basis to determine the sustainable harvest rate. Daily harvesting at 30% maintained the rotifer culture at its stationary phase (381 ± 19.45 rotifers/mL) throughout the experiment. Following use in the RAS, the harvested water was treated using a series of filters (sand, cartridge, and ultraviolet filters) and was reused for algal culture. The results suggested that critical water quality characteristics, including pH (7.4–8.4), dissolved oxygen (3.8–6.8 mg/L), and un‐ionized ammonia (<0.5 mg/L), remained within acceptable limits. We conclude that the freshwater rotifer B. calyciflorus can be produced on a commercial scale by adopting advanced RAS‐based technology with minimum water waste.

Barbs are India's native group of ornamental fish, and it has a wide recognition in the global ornamental fish trade (Sarkar & Lakra, 2010).Barbs come under Cyprinidae family, which is the largest freshwater family and widely distributed around the world. Barb's attractive colour and shape, large scales, schooling behaviour, easy to maintain and breed qualities have made them popular in the aquarium trade (Tamaru, 1997). Puntius species are popular at international level because of their striking colours and attractive shape (Collins, 2012).Dawkinsia rohani synonym of Puntius rohani (Devi et al., 2010) is a cyprinid fish native to Kanyakumari District, Tamil Nadu, India. It is an endemic ornamental barb of the Western Ghats and inhabits the hill streams of Kanyakumari District in Tamil Nadu draining into the Arabian Sea (Devi et al., 2010). Dawkinsia rohani has been reported to be under several potential threats like urban development, tourism, invasive species, agricultural pollution and excessive harvesting (Dahanukar, 2015). The Rohan's Barb is listed under 'vulnerable' on

Moustached danio, _Danio dangila,_ is a potential ornamental fish of India but the stock of this endemic Cyprinid is declining in the wild due to environmental variation and anthropogenic activities. Hence, the present work on induced breeding and larval rearing was undertaken to conserve this species. During the investigation, live fish were brought from Assam (North-East Indian region) to ARTP, Chennai, Tamil Nadu. In experiment 1, trials to breed the species using the synthetic hormone WOVA-FH, since the species did not respond to breed in captivity, revealed the highest spawning (1002.50±52.6), fertilization (84.0±2.72%) and hatching rate (86.5±2.9%) after intraperitonial injection at 0.5 ml/kg for females and 0.3 ml/kg for males. In experiment 2, larval rearing in nursery raceways and FRP tanks at different stocking densities for 45 days showed that the RAS-based nursery raceways produced the highest survival (91.79±1.67%) and specific growth rate (0.13±0.001%/day) at 30 numbers/L stocking density. The present investigation standardized the breeding and larval rearing protocol in advanced aquaculture systems and can give significant implications on the conservation and seed production of the species.

Aquaculture is gaining commendable importance to meet the required protein source for ever increasing human population. The aquaculture industry is currently facing problems on developing economically viable production systems by reducing the impact on environment. Sustainable and enhanced f ish production from aquaculture may be better achieved through application of recent biotechnological innovations. Utilisation of transgenic technology has led to production of f ishes with faster growth rate with disease resistance. The full advantage of this technology could not be achieved due to concern of acceptance for Genetically Modif ied Organisms (GMOs). The biotechnological intervention in developing plant based feed ingredient in place of f ish meal which contain high phosphorus is of prime area of attention for f ish feed industry. The replacement of f ish meal will also reduce f ish feed cost to a greater extent. Year round f ish seed production of carps through various biotechnological interventions is also need of the hour. This paper discusses technical, environmental and managerial considerations regarding the use of these biotechnological tools in aquaculture along with the advantages of research application and its commercialization.