A SURVEY ON THREE TROUT FARMS PHOSPHORUS LOADING INTO HARAZ RIVER, NORTH IRAN

A monthly survey on phosphorous loading due to fish farm sewage was conducted from July 2003 to June 2004 in Haraz River. In total, 88 water samples from eight stations and spots up and down of the three fish farms were sampled. The measurement of the phosphorous was carried out by spectrophotometer method (Hitachi, U- 2000 Model). Results showed that the fish farms had effective role in increasing phosphoric load in Haraz River.
We found a significant relationship between the orthophosphate (P<0.007) and total phosphorous (P<0.049) released up the station and the station itself. Net variation in phosphate and total phosphorus of the first farm (100 tons production capacity) was recorded as 13.9kg/day and 21.99 kg/day respectively. The same parameters for the second farm (80 tons production capacity) were 7.95kg/day and 15.08kg/day, respectively. The third farm (40 tons production capacity) showed a net variation in phosphate and total phosphorus of 2.28kg/day and 3.63 kg/day, respectively. Organic phosphorus was calculated as 40% for the first farm, 700 meters distance from the other farm, and 47% for the second farm, 300 meters down the other farm. For the third farm with a distance of 6000 meters from the other farm, the organic phosphorous was 37%. We believe that these changes are related to the farm distance, production capacity, and food type used in the farms.