Limnological study of Taham lake in Zanjan province in order to assess aquaculture possibility

Abstract

The Taham dam reservoir has been established in order to provide drinking water of Zanjan population as far as 15 km in a mountain region at 1900 meter altitude with a 317 ha surface area. This study was conducted on biotic and a biotic factors in order to recognize of aquaculture possibility within drinking considerations. The results showed the less abundance of phytoplankton with 2 million/l. where abundant of zooplankton was 266 /l. Bacillariophyta and Chlorophyta belong to phytoplankton and Rotatoria belong to zooplankton were dominated among identified plankton phylum. There were identified 45 and 32 genus of phytoplankton and zooplankton respectively. There were identified 5 groups of benthos that Tubificidae, Hirudina had the most frequency, and the biomass of benthos was varied from 1.1 to 23.7 g /m2. The ichtiology survey showed presence of 6 species in the lake that Alburnoides bipunctatus, Capoeta capoeta, , Leuciscus cephalus were the most abundance in the catch. L. cephalus was recorded with the maximum size of 870 g while the most frequent weight class was 150 450 g for C. capoeta,, L. cephalus . Diet survey showed the adequate feeding of fishes in lake also the observation of leech in trout guts was very considerable. The reproduction study displayed that a partial of matured fishes were succeed in breeding. Leuciscus cephalus have been known as a typical species with commercial size and high abundance which will be needed a fisheries management in Taham Lake to sustainable exploitation. The hidrochemical results indicated low nutrients values while total nitrogen was varied from 0.32 to 0.61 mg/l. and the Chl-a was varied from 7.9 to 25.9 μg/l.. The oxygen amount was 4.5 to 8.4 mg/l even in 65 meter depths. Total hardness average was about 149 mg/l where the Ca and Mn were measured in a low values. Trophic model in Taham lake showed the early stage of mesotrophy while other lakes and wetlands in north of Iran had been progressed in mesotrophic level.