Influence of water alkalinity in production of stunted fingerlings of Catla catla (Hamilton).

Abstract

Study was conducted for 90 days to know the effect of varying water alkalinity in production of stunted fingerlings of Catla catla in outdoor FRP tanks (1000 litre). Tanks filled up to 800 litre marks were grouped into three triplicated treatments and were stocked with catla seed (3.9g, 67±0.27mm) at 16 nos per tank (20 m-3). Three alkalinity levels, i.e. 80, 150 and 200 mg CaCO3 L-1 were used and designated as Control, T-1 and T-2, respectively. Pond water (80 mg L-1) and bore well water (360 mg L-1) were used as the two sources to get the desired alkalinity level. Fishes were fed with powdered feed @ 8% of their respective biomass in all the treatments. The survival of catla decreased significantly (p<0.05) with the increase in alkalinity from control (97.92±3.61%) to T-2 (89.58±3.61%). The average harvested body weight and length in T-1 (8.83±0.40g, 8.73±0.17cm) and T-2 (8.28±0.19g, 8.65±0.10cm) were similar (p>0.05), but both were significantly lower than the control (9.64±0.12g, 9.02±0.02cm). Similarly, specific growth rate of T-1 (0.91±0.05) and T-2 (0.84±0.03) were similar and significantly lower than control (1.01±0.01). The biomass yield also reduced significantly with increase in alkalinity from control (151.00±4.63g) followed by T-1 (132.43±6.06g) and T-2 (118.77±7.56g). Such results indicated pronounced effect of increased alkalinity on suppressing fish growth and suggested possibility of manipulating this parameter as a tool for stunting of catla seed.