RELATIONSHIP BETWEEN PHYTOPLANKTON, ZOOPLANKTON AND FISH CULTURE IN A FRESHWATER FISH FARM

Abstract

T his study was carried out at the Barrage Fish Farm during 2001 farming season. It was performed to evaluate the plankton communities and the effect of fishponds on their standing crop and species composition. The data revealed that the phytoplankton communities are represented by five classes namely Chlorophyceae,BaciHariophyceae, Cyanophyceae, Dinophyceae and Euglenophyceae. Their major peak was observed at Pond 6 while the minor one was found at Pond 5. With regard to the monthly variations, phytoplankton communities flourished in July while their minimum occurrence occurred in September and August. The zooplankton species belonged to rotifers, cladocerans, and copepods in addition to the meroplanktonic forms. Rotifers were most common in all ponds. It constituted 94.64% of total zooplankton in the ponds. Copepoda occupied the second predominant position and contributed 4.23% of total zooplankton crop. Cladocera was dominated by Moina micrura. The average zooplankton number at the ponds was 258.4 orgT , their major peak of 1073 org.l" 1 was observed at Pond 3 in April, while the minor one of 20 org.1" 1 occurred at Pond 5. Fish culture had obviously influenced the intraplanktonic dynamics, Chlorophyceae occupied the first predominant position at the fishponds and constituted about 60% of the total crop followed by Bacillariophyceae (25.8%) and Cyanophyceae (14%). Diatoms replaced green algal position at the River Nile water and contributed about 70% of the total numerical density. The small rotifers and nauplius larvae of copepods were the most dominant in fishponds in spite of the large forms in the main feeder.