Primary Productivity Studies on Freshwater Fish‐Ponds of Bhagalpur, India

Abstract

A one year study from October 1972 to September 1973 in four freshwater fishponds of Bhagalpur (87° 02' E long, and 25° 15'N lat.), India, has shown that a high phytoplankton primary production occurred twice during the annual cycle. There were seasonal variations in the production rate with a great fluctuation in the maximum and minimum values (3 … 4 times). Amongst the ponds studied, the highest daily production recorded was 6.93 g C/m2/day in Pond I and the minimum was 0.82 g C/m2/day in Pond II. The highest annual gross production was estimated to be 1611.98 g C/m2/y in Pond I, next in the order was 1543 g C/m2/y in Pond IV and then 1155.7.5 g C/m2/y in Pond I and the minimum was 641.75 C/m2/y in Pond II. It has also been observed that in certain months the net:gross ratio recorded was zero, while the community respiration as percentage of the gross production value reached 100% in few months. A comparison has been made in the annual production of temperate and tropical freshwater systems and this indicates that tropical waters are more productive than the temperate waters. Various physico‐chemical factors such as rainfall, light, temperature and alkalinity may regulate or limit production.