Vast application of the antibiotic drugs in animals without due attention  to withdrawal times necessitates quality control of food stuff in terms of antibiotics' residues. Antibiotic residues in food stuff cause bacterial resistance, allergic reactions, toxicity,  carcinogenic effects and change of natural micro flora of intestine in consumers. So, the aim of the present study is detection of antibiotic residues and its contamination rate in cultured rainbow trout.

Four-plate test is one of the microbiological methods of detecting antibiotic  residues  in food stuff, which is based on inhibition zone formation around the sample in four culture media with different pH and test bacteria. For this purpose, 45 samples from skin and meat of rainbow trout fish were obtained randomly from fish market of Tabriz city. After different phases of four-plate test, from a total of 180 skin samples, 13 cases (7.22%) and from a total of 180 meat samples, 18 cases (10%) were diagnosed to be contaminated to antibiotic residues.

The results showed that contamination rate of two tissues, (meat and skin), have no significant difference (P>0.05), and the highest contamination to antibiotic residues  were related to penicillin and macrolides groups (P<0.05).

Water reservoirs are an important to the supply of drinking water and agriculture. In Iran, study of water quality in the dam has been considered in recent years. This study was conducted to determine water quality of Azad Reservoir (Kordestan-Sanandaj) based on Iranian water quality (IRWQI) and Carlson trophic (TSI) indices. Sampling was carried out at five stations during different months in 2015-2016. Results showed that mean (±SE) of NO3, NH4, TP, PO4, DO%, pH, EC, SDD, TH, BOD5, COD and Chl-a were observed 0.21±0.01, 0.048±0.004, 0.030±0.001, 0.016±0.001 mg/l, 114±3 %, 7.89±0.37, 290±40 µS/cm, 2.00±0.14 m, 138±1, 2.18±0.19, 9.28±1.13 and 4.73±0.73 mg/l, respectively. Result showed that trophic status of Azad dam was mesotrophic based on chl-a parameters and eutophic to hypertrophic based on other variables (TP, SDD, DO%) at bottom layers of some stations. Mean of Carlson trophic status was represented mesotrophic (high quality) at Azad dam. Based on IRWQI, water quality of dam was classified excellent quality. Although, mean of indices was suitable for drinking water and agriculture activities but due to decline water quality and increased trophic levels in some months, it is necessary to apply appropriate management strategies for maintaining of water quality of the reservoir.