Condition of labeo rohita and primary productivity of surya- pokhra pond (manpur), gaya, bihar

It is a hard fact that condition factor in fishes (Rohu) which is studied, shows marked fluctiuations during the year, so much so that on the basis alone the year can be broadly divided into four important periods like, the winter (January to March), the pre-monsoon (April to June), the monsoon (July to September), and the post monsoon (October to December). The condition of fish productivity in general is good particularly during the winter and pre-monsoon months. The reason is that the food environment is favourable during the pre-monsoon period. The adult fishes are sexually matured. There are deposition of fats in the body. Various ecological conditions also play an important role for increase in the weight of fishes. Pond water is also observed as clear, transparent and less polluted. The slight degree of pollution is due to human activities. Abundance of phytoplanktons also provide the improved feeding condition as a number of phytoplanktons like Chlamydomonas, Oscillatoria etc. are observed. Dissolved oxygen also showed similar pattern of wide fluctuations with range between 6.8 to 13.8. The first peak was found during March’ 2018 and other during September’ 2018 . The lowest value was recorded as 6.8 ppm in June’ 2018 . The high dissolved oxygen content in Aug-Sep can be attributed to the phenomenon of photosynthesis accentuated by high velocity of flow and presence of abundant quantities of macrophytes and cloud free sky, which cause good photosynthesis activities in the ecosystem. The collected data also shows there is decrease in D.O. with increase in temperature throughout the year.