fa aquaculture aquaculture پژوهشي Orginal research papers <p>The objective of this study was to compare growth performance and feed conversion ratios of rainbow trout (<em>Oncorhynchus mykiss</em>) and brook trout (<em>Salvelinus fontinalis</em>) juveniles in monoculture and duo-culture in freshwater and seawater under aquarium conditions. The fish were about 2-months old hatchery-reared brook and rainbow trout with initial weights of 0.934&plusmn;0.033 (n=360) and 1.014&plusmn;0.019 (n=360) g, respectively. The juveniles were kept in 10 L aquaria. Each aquarium contained 40 fish: 40 fish from each species for monoculture, 20+20 (rainbow trout+brook trout) fish from each species for duo-culture. The fish were in 3 groups with three replicates in freshwater and seawater and 18 aquaria were used. At the end of the 45 day study; mean live weights of brook trout were 2.735&plusmn;0.153 g, rainbow trout 2.925&plusmn;0.262 g in monoculture and brook trout 2.354&plusmn;0.186 g, rainbow trout 3.882&plusmn;0.494 g in duo-culture in seawater, brook trout 3.088&plusmn;0.085, rainbow trout 3.364&plusmn;0.093 g in monoculture and brook trout 2.164&plusmn;0.169, rainbow trout 3.948&plusmn;0.124 g in duo-culture in fresh water. While there were similarities between brook trout and rainbow trout in monoculture groups in sea water and fresh water, some differences were realized in duo-culture (<em>p</em><0.001).</p> Rainbow trout, Oncorhynchus mykiss, Brook trout, Salvelinus fontinalis, Polyculture, Growth Performance, Feed conversion ratio 38 49 http://jifro.ir/browse.php?a_code=A-10-600-52&slc_lang=fa&sid=1 F. Delihasan Sonay 100319475328460020091 100319475328460020091 Yes N. Başçınar 100319475328460020092 100319475328460020092 No