The Asian Cichlid E. suratensis popularly known as pearlspot is a native of South India and Sri Lanka, contributes to a major fishery in the inland waters of Kerala. The commercial importance and the local preference led the state government of Kerala to declare pearlspot as the State Fish in the year 2010 and the year 2011-12 was declared as the 'Year of Pearlspot'. High market demand together with assured economic benefits (Rs. 400-600/kg) and easily adoptable technology makes the species an ideal candidate for small scale fish culture in Kerala, using locally available inputs. Being an omnivorous fish, the culture of the species is supported by low cost farm made feeds and no special skills or interventions are required at any stage of culture. Major constraint in the expansion of aquaculture is the absence of a viable formulated feed for the species, suitable for use in cages. Farmers use a variety of materials depending on local availability and cost effectiveness, irrespective of the nutritional requirement of the species. An appropriate formula for farm made feed is the need of the hour to tackle the co-existing problems of nutritional requirement of the species and its affordability to farmers.
The present study was designed to examine the effects of ulva meal on growth performance, proximate composition, and feeding efficiency at different levels (0.0, 25.0, 50.0, 75.0, and 100.0 g kg-1) in Etroplus suratensis feed. 70 days long feeding experiment was conducted in net cages (4/3-16mm-1m x1m x 1.25m) at Government fisheries farm Ayiramthengu, Kollam, Kerala, with 500 nos. of Etroplus juveniles (avg. length, 4.47±0.48 and avg. weight 2.37±0.75) divided into five duplicate groups of 50 fish per replication and randomly stocked in 10 net cages suspended 30 cm off the bottom in large concrete tanks at the farm. Five test diets were formulated, control Ulva-free diet (U1) and varying levels of Ulva meal: 25 g kg−1 (U2), 50 g kg−1 (U3), 75 g kg−1 (U4), and 100 g kg−1 (U5) to partially replace wheat flour. Feeds were formulated by Pearson square method, containing approximately 30% crude protein and 5-6% crude lipid, fulfilling the requirement for Etroplus suratensis. Test diets were fed twice daily, at 09:00 and 17:00, at 7-10% BW for 10 weeks. Fish were weighed every 10th day from the beginning of the study. The water quality parameters of the culture site were monitored at weekly intervals. The proximate composition of test diets and the initial and final composition of experimental fishes were carried out. The growth parameters were estimated and subjected to statistical analysis. The results of the study show that growth parameter were significantly different in all the treatments (P<0.05). The 25g/kg incorporation level of ulva shows higher weight gain followed by 50g/kg level, 100g/kg incorporation level shows lowest weight gain compared to control. Highest SGR and best FCR were observed in 25g/kg incorporation level, higher values of FCE was found in 75 g/kg Ulva incorporated feeds. Fishes fed with 2.5% - 7.5% ulva meal level shows good performance compared to control and 10 % fed groups. Study suggests that Ulva meal up to 7.5% can be incorporated in Etroplus diets without impairing growth and feed utilization efficiency, incorporation level of 2.5% gives better results in the present study. Being a macrophytic feeder on most of the ecosystems, the Ulva spp. can be utilized as a feed component in Etroplus cage culture practices. This work could encourage farmers can use the locally available Ulva spp. as a feed source for E. suratensis in cage culture to reduce feed costs.