Effect of C/N Ratio Levels and Stocking Density of Catla Spawn (Gibelion catla) on Water Quality, Growth Performance, and Biofloc Nutritional Composition in an Indoor Biofloc System
Sonia Solanki, S. J. Meshram, H. B. Dhamagaye, S. D. Naik, P. E. Shingare, B. M. Yadav
Abstract
A 20-day 3 ∗ 3 factorial experiment was conducted in 100 L HDPE experimental tanks to investigate the effect of the C/N ratio (10, 15, and 20) and stocking density (3, 4, and 5 spawn L−1) on Gibelion catla spawn nursery rearing in the indoor biofloc system. Rice bran was used as the carbon source for manipulating C/N ratios. Each treatment was stocked with catla spawn of average length (6.7 ± 0.4 mm) and average weight (1.6 ± 0.2 mg). Water parameters showed that increasing the C/N ratio from 10 to 20 significantly ( <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" id="M1"> <a:mi>p</a:mi> <a:mo><</a:mo> <a:mn>0.05</a:mn> </a:math> ) reduced total ammonia nitrogen (TAN) and nitrite nitrogen (NO2-N) and increased nitrate nitrogen (NO3-N) in the water. The insignificant difference ( <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" id="M2"> <c:mi>p</c:mi> <c:mo>></c:mo> <c:mn>0.05</c:mn> </c:math> ) and lowest final average length, average length gain, average weight gain, and specific growth rate (SGR) were recorded in C/N ratios of 10 and 15 compared to a C/N ratio of 20. A significant difference ( <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" id="M3"> <e:mi>p</e:mi> <e:mo><</e:mo> <e:mn>0.05</e:mn> </e:math> ) in survival was observed with the increasing C/N ratio. Increasing the fish stocking density resulted in higher mortality. However, a higher amount of fry produced was observed in the treatments with 3 and 4 spawn L−1. Crude protein content increased significantly ( <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" id="M4"> <g:mi>p</g:mi> <g:mo><</g:mo> <g:mn>0.05</g:mn> </g:math> ) with the increasing C/N ratio with higher content in C/N 20. No significant difference ( <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" id="M5"> <i:mi>p</i:mi> <i:mo>></i:mo> <i:mn>0.05</i:mn> </i:math> ) in proximate composition of biofloc was observed in different stocking density groups. In conclusion, the application of the biofloc technology with a C/N ratio of 20 at a stocking density of 4 spawn L−1 could be recommended to increase the production of catla fry in the indoor biofloc system.