Evaluation of Bamboo, Coconut Shell Substrates and Supplemental Feeding on the Growth of Pearlspot, Etroplus suratensis (Bloch) Fry in Low Volume Cages

Abstract

The 90 days experiment aimed at understanding the scope of utilising periphyton substrates for cage culture of pearlspot fry. The experiment evaluated coconut shells relative to bamboo as periphyton substrates for pearlspot culture. The experiment constituted six floating cages (1x0.75x1 m3) each partitioned into two to get 12 experimental units into which 360 pearlspot fry (avg. wt. 3.55±0.17 g) were equally distributed. The experiment constituted of four treatment; TB: substrate (bamboo-strip mats), TC: substrate (coconut shells), TB+F: substrate (bamboo-strip mats) + supplementary feed,TF: supplementary feed, in triplicates. The substrates provided a surface area of ~ 1.9m2 unit-1. Feeding in TB+F and TF was done using commercial carp feed (crude protein- 32%; crude lipid- 5%) twice daily approximately at 10% of the body weight initially upto 30 days and subsequently the feeding rate was reduced to 9 and 8% of body weight after 30 and 60 days respectively. Sampling was conducted every 15 days to assess fish growth and survival. Relatively higher specific growth rate (SGR) recorded in TB+F over TF during the initial phase of the experiment indicated the ability of pearlspot to utilise periphyton efficiently in the early stages. Final SGR of 1.2 and 1.5% day-1 in TC and TB respectively indicates that periphyton can support the growth of pearlspot. Higher SGR and percentage weight gain in TB (1.50±0.07% day-1; 288.10±26.69%) relative to TC(1.26±0.12% day-1; 215.90±36.37%) shows that bamboo is superior periphyton substrate for pearlspot culture. Lower yet statistically similar growth rates of pearlspot in Tc relative to TB together with low cost and easy availability of coconut shell substrates indicates that these could be used as alternative periphyton substrates for fish culture.