Evaluation of Growth, Survival, and Production of an Endangered Fish, Labeo gonius (Hamilton) Fingerlings in Earthen Nursery Ponds

Abstract

ABSTRACT Nursery rearing of an endangered fish, Labeo gonius (Ham.) was studied in relation to varying stocking densities in earthen ponds. The experiment was conducted for 8 weeks in nine nursery ponds having an area of 0.012 ha with an average depth of 1 m. Four-day-old hatchling stocked at 0.6 million/ha was designated as treatment-1 (T1), 0.8 million/ha as treatment-2 (T2) and 1.0 million/ha as treatment-3 (T3), respectively. At stocking, all hatchlings were of same age group with a mean length and weight of 0.66 ± 0.08 cm and 0.001 ± 0.0001 g, respectively. Hatchlings in all the experimental ponds were given wheat flour for the first 7 days, finely ground mustard oilcake for the next 7 days and a mixture of rice bran, and mustard oilcake (1:1) for days 15 to 56. The rate of feeding was 20 kg/million hatchling/day for the first two weeks, 25 kg for the second two weeks, 30 kg for the third two weeks and 35 kg for the fourth two weeks. The physicochemical parameters of water and plankton were monitored simultaneously and were within the acceptable range for fish culture. Growth parameters (final weight, final length, weight gain, length gain and specific growth rate) and survival of fingerlings were significantly higher in T1 (0.6 million hatchling/ha) than those in T2 (0.8 million/ha) and T3 (1.0 million/ha), respectively. Feed conversion ratio (FCR) was significantly lower in T1 followed by T2 and T3 in that order. The estimated gross and net productions of fingerlings were significantly higher in T1 than in T2 and T3, respectively. Significantly higher number of fingerlings was produced in T3 than those in T2 and T1. Despite this, consistently higher net benefits were obtained from T1 than from T3 and T2. Overall, highest growth, survival, production and benefits were obtained from T1 where stocking density of hatchlings was 0.6 million/ha. Hence, of the treatments evaluated, stocking density of 0.6 million hatchling/ha appears to be the most efficient stocking density for rearing of L. gonius fingerlings in earthen nursery ponds.