Fish And Phosphorus Distribution In Typical Reservoirs Of Guangdong Province During Dry Season

To understand the effects of fish on phosphorus distribution in water column and the response of Chlorophyll a to phosphorus variation, field investigations were performed in 20 reservoirs of Guangdong province from October, 2014 to January, 2015. We examined fish species, fish density and biomass, phosphorus in different particle(>200 μm, 20~200 μm, <20 μm) and Chlorophyll a in water columns. We analyzed the relationship between fish density and concentration of particle phosphorus. The results were::1) Total phosphorus concentration ranged from 8.7~86.4 μg/L, the conttribution of meso-and macrozooplankton(>200 μm), microzooplankton(20~200 μm) and nano-and picophytoplankton(<20 μm) to total phosphorus were 0.19%~7.13%, 1.73%~19.54% and 55.2%~94.1%, respectively.2) Chlorophyll a concentration ranged from 1.1μg/L to 34.0 μg/L, and the mass ration of Chlorophyll a to phosphorus ranged from 0.09 to 0.98. Chlorophyll a concentration was significantly correlated with total phosphorus concentration(P < 0.05).3) The common fish in the 20 reservoirs were: Aristichthys nobilis 、Hypophthalmichthys molitrix, Oreochromis, Hemiculterella sauvagei, Hemiculter bleekeri, Cirrhinus molitorella, Parabramis pekinensis, Ctenopharyngodon idellus, Labeo rohita, Carassinus auratus. Total fish density ranged from 0.0006~0.094 ind./m3, most were small fish with body length less than 20 cm which contributed 55.6%~98.1% to total fish density,. Total fish biomass ranged from 0.26~36.8 g/m3, most were big fish with body length more than 20 cm which contributed 47.0~97.9% to total fish biomass. Fish density showed significant correlation with total phosphorus concentration and mass ratio of Chlorophyll a to phosphorus(P < 0.05).4) Strong grazing pressure of planktivore fish on zooplankton caused the phosphorus of water column mostly distributed in phytoplankton and high mass ratio ofChlorophyll a to phosphorus in the reservoirs.