Herotrophic Bacterial Populations and Primary Production In Fish Ponds Under Different Manaement Practices

Abstract

The aerobic heterotrophic bacterial populations in the water and sediment media and primary production levels with reference to the physicochemi cal conditions of carp polyculture ponds under different management practices, viz. , fortnightly application of cowdung in heaps, spray-application of cowdung on alternate days, gradual leaching of inorganic fertilizers, manual raking of pond bottom and bioturbation by common carp, were studied, along with observations on the growth characteristics of bacterial populations under simulated conditions. The bacterial counts were maximal in the ponds with agitated bottom, inspite of the absence of allochthonous organic enrichment. The generation time and generation number of the populations in the water and sediment media were in the ranges of 0.9-24.8 h, 0.7-21.2 h and 0.2-5.3, 0.2-6.4 respectively, indicating intense bacterial activities . Primary production levels in the ponds were moderate (1.13-3 6.77 g c/m3/d ) , comprising high (31.27-139.82%) respiration values. The results brought out the significance of the heterotrophic food chain in f i s h pond ecosystems and demonstrated the positive effects of simple pond environmental man ipu l a t ion measures like bottom raking on sediment-water interactions .