Changes of Water Quality due to Jute Retting and its Impact on the Fingerlings of Rui (Labeo rohita)

Abstract

This project thesis deals with the study of degradation of jute (retting practice) in fresh water environment and its effects on water chemistry and consequently on aquatic organisms of fresh water environment. Six ponds named P-1, P-2, P-3, P-4, P-5 and P- 6 and each with (18×12×4) feet in size were selected for rearing the fry of Labeo rohita at an initial weight and length of 2.29 0.05 gm and 6.21 ± 0.05 cm respectively and also with a stocking density of 40fry/pond. The fry were reared in the experimental ponds without supplementary feeds. After five days of Labeo rohita fry stocking jute plants with leaves were collected as bundles. Each bundle consisted of 60 plants weighting 25 Kg. Jute bundles steeped into water in heaps for retting at the rate of 7 bundles in the experimental ponds P-4, P-5, P-6. The retted bundles were collected from the ponds after 21 days and fibre was separated from stalks at a time manually. The water quality parameters namely pH, temperature, salinity, dissolved oxygen (DO), hardness, alkalinity, chloride (CI) and free CO2, survivility of fry were determined six times with nearly weekly intervals. The study supports the degradation jute plants followed by reduction of dissolve oxygen and evolution of free CO2. The present study reported that the fluctuation of above water parameters due to jute retting practiced in the experimental ponds have lethal effect to the Labeo rohita fry. This might be due the rapid change of water parameters in the 2 week when fry in P-4, P- 5, P-6 were subjected to death. The parameters of stagnant water environment fluctuate highly at 2nd week due to the jute fibre decomposition and it come back to the prior stage slowly.