Spatial and Seasonal Variation of the Primary Productivity in the Major Nursery Grounds of Hilsa (Tenualosa ilisha)

Abstract

The present study was conducted to estimate the primary productivity of major nursery grounds of hilsa both spatially and seasonally. Gross primary productivity (GPP), net primary productivity (NPP), and community respiration (CR) were estimated in summer, rainy, and winter, respectively. The maximum GPP (0.68 gCm-3h-1) and NPP (0.27 gCm-3h-1) were noted during summer season and minimum (0.31 gCm-3 h-1 and 0.19 gCm-3 h-1) in rainy season at all the six stations. The annual average GPP varied from 0.36±0.008 gCm-3h-1to 0.70±0.1 gCm-3h-1. The NPP value varied from 0.23±0.001 gCm-3h-1to 0.51±0.09 gCm-3h-1and exhibited an increasing trend from the month of March to June. CR ranged from 0.12±0.003 gCm-3h-1 to 0.20±0.05 gCm-3h-1 and exhibited an increasing trend from the month of January to May whereas the study found that the CR has also seasonal pattern with maximum and minimum value during summer and winter respectively at all the stations.The data of primary productivity at all stations showed that except S6, all stations has a good nutrient profile and suitable for hilsa production.