Investigation of growth performance and feeding efficiency of rainbow trout (Oncorhynchus mykiss) in floating cages in the southern Caspian region

Information on the aquaculture of rainbow trout Oncorhynchus mykiss in brackish water, especially in the Caspian Sea, is very limited. In this study, the growth performance and feeding efficiency of rainbow trout in an enclosed environment (5 floating cages) in an offshore farm (5 km distance from the beach) in the southern Caspian Sea region were investigated. This study was performed in Mehrangostar Caspian Sea farm in the Tuskatok area of Nowshahr City, Mazandaran Province, Iran. The fish were introduced to the cages with a density of 21 fish/m3 and also biomass of 3.33 kg/m3 and weight of 110 to 180 g. The duration of the rearing period and the average survival rate of fish were 123-158 days and 95.8 ± 0.5%, respectively.  In addition, the feed conversion ratio and protein efficiency ratio were 0.94 ± 0.01 and 2.66 ± 0.01, respectively. In this brackish farm, the fish average daily growth rate and the average specific growth rate were 3.3 ± 0.9 g/day and 1.07 ± 0.01%/day. Moreover, the average weight of fish yield was 16 kg/m3. The results showed that the growth trend of rainbow trout in the brackish water of the Caspian Sea in floating cages was suitable. Therefore, the introduction of rainbow trout to floating cages in the southern Caspian Sea by different weights, density of 3.33 kg/m3 and also by managing the harvest of 15 kg/m3 in different times or in a whole single catch is quite possible

A study on water quality and physio- chemicals parameters in surface water, underground water and wastewater of Mangol dam basin (Mazandaran province)

This study was conducted to determine water quality of surface water (7 stations), ground water (5 stations) and wastewater (4 stations) at Haraz River during instruction of Mangol Dam in 2009-2010. This study is to follow physico-chemical fluctuation of waters and compared the data obtained with previous studies and standard levels. Results of current study showed that annual mean with standard error of temperature, DO, BOD_5, COD, HCO^3-, CO_3^2-, TA, Ca^2+, Mg^2+, TH, TSS, TDS, Cl^-, PO_4^3-, NH^4+, NO2- and NO3- were observed 12.7 (±0.61) centigrade, 10.13 (±0.12), 2.1 (±0.1), 7.71 (±0.99), 28.1 (±6.1), 14.34 (±1.64), 36.30 (±2.33), 64.66 (±2.34), 28.84 (±1.52), 271.62 (±8.41), 0.37 (±0.03), 0.30 (±0.02), 28.02 (±1.96), 0.06 (±0.01), 0.010 (±0.001) and 0.94 (±0.03) mg/l, pH was 8.00 (±0.02) and EC 0.50 (±0.02) ms/cm in surface water. The annual mean with standard error of temperature, HCO^3-, CO_3^2-, TA, Ca^2+, Mg^2+, TH, TSS, TDS, Cl^-, PO4^3-, NH^4+, NO^2- and NO^3- were observed 21.62 (±1.03) centigrade, 54 (±5), 11 (±5), 57 (±5), 208.6 (±42.5), 109 (±23), 1088 (±165), 0.065 (±0.017), 0.97 (±0.11), 317.8 (±76.2), 0.25 (±0.06), 0.06 (±0.01), 0.0007 (±0.0001) and 0.78 (±0.05) mg/l, pH was 7.37 (±0.07) and EC 1.98 (±0.23) ms/cm in underground water. In addition, the annual mean with standard error of temperatute, DO, BOD5, COD, TSS, TDS, and NO3- were observed 12.7 (±0.61) centigrade, 13.59 (±0.87), 9.80 (±0.12), 2.22 (±0.18), 7.54 (±1.02), 0.50 (±0.03), 0.320 (±0.008) and 0.990 (±0.016) mg/l, pH was 7.95 (±0.02) and EC 0.64 (±0.01) ms/cm in wastewater. Quality of surface water of Haraz River and its branches were almost contained suitable for usual applications, but sometimes the quality of surface water based on BOD5 need to more attention for man uses (such as supply of drinking water). In addition, the quality of surface water was relatively suitable for aquatic based on the aquatic standard levels. Results also showed that water quality index (WQI) was declined from upstream to downstream and some parameters were not in standard ranges. The quality of surface water classified in group II at all stations based on water classification rules which it shows serious water quality changes due to environmental destroyed and domestic, agriculture sewage pollutions. Groundwater were affected by different springs at middle and downstream which they caused change physico-chemical characteristics and water quality. Wastewater was classified from good to moderate based on BOD5. The quality of wastewater was declined at downstream with decreasing DO and pH and increasing BOD5 and pollutants