Use of Additional Substrate to Enhance Growth Performance of Milkfish, Chanos chanos (Forsskal) in Inland Saline Groundwater Ponds

Abstract

Milkfish, Chanos chanosfingerlings were cultured in inland saline groundwater ponds. Bamboo poles as additional substrate were used to increase the surface area of the ponds (Treated ponds). Controls, without the provision of additional substrate, were also maintained. After a culture period of 60 days, significantly (P < 0.05) higher growth was observed in treated ponds (mean fish wt. 86.6±2.4 g; SGR 1.5±0.01) as compared to controls (mean fish wt. 50.2±1.2 g; SGR 1.0±0.1). Length-weight relationship showed high exponential value (n) of length in treated ponds (n = 2.49) in comparison with controls (n = 1.63). Significant differences in most of the water quality parameters were not observed between the two treatments; however, turbidity, NH4-N, net primary productivity, chlorophyll apheophytin aand zooplankton population were significantly (P < 0.05) higher in controls. Significantly, (P < 0.05) high periphyton biomass in terms of dry matter (DM) (1.5±0.02 mg/cm2), chlorophyll a (13.5±1.1 μg/cm2), pheophytin a (8.3±1.2 μg/cm2) and mean periphyton productivity (1.4 mg C/m2/day) were observed at a depth of 50 cm in treated ponds. Autotrophic index was significantly (P < 0.05) low at 50 cm depth than at the other depths. Low values of epilithic periphyton density in ponds provided with additional substrate indicate the incorporation of planktonic flora and fauna in periphyton development. These investigations thus clearly suggest that the provision of additional substrate in culture ponds resulted in higher yield of milkfish.