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

Document Type : Research Paper


Agricultural Research, Education and Extension Organization, Iranian Fisheries Science Research Institute, Caspian Sea Ecology Research center, Aquaculture Department, Sari, Mazandaran, Iran


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.