Cage culture of Etroplus suratensis (Bloch, 1790) in a tropical reservoir in India and associated impacts on water and sediment quality

Abstract

Cage culture of Etroplus suratensis (Pearlspot) was carried out in Krishnagiri reservoir, India, a highly productive reservoir to analyze the feasibility of growing this species in freshwater cages and to investigate the effect on selected environmental parameters. Fish of average weight 5.98 ± 0.52 g were stocked at 10 ind. m3 in High-Density Poly-Ethylene floating cages (3 × 3 × 2 m) made of nylon knotless net with 12 mm mesh size. Fish were fed commercial pellet feed containing 32% protein at 5–3% of body weight a day. A reference point was fixed 100 m away from the cage site to compare the water quality as well as plankton abundance with the cage site. After 7 months, the fish grew to 90.31 ± 2.48 g, with low mean weight gain during the first 2 months, and a steady increase thereafter. Overall, the growth of Etroplus in terms of the analyzed parameters viz. specific growth rate, food conversion ratio, feed efficiency ratio, and protein efficiency ratio viz. 1.3 ± 0.013, 2.87 ± 0.08, 0.35 ± 0.01 and 1.01 ± 0.03, respectively, was found to be satisfactory in freshwater cages irrespective of low survival (52%). Zooplankton and phytoplankton density at the cage was significantly higher throughout the study, maybe due to the abundance of primary nutrients from the decomposition of leftover feed.