Rainbow trout (Oncorhynchus mykiss) fry initiation in closed water recirculation systems

Background: rainbow trout is widely accepted for human consumption worldwide, however, its culture requires large quantities of high quality water. Objective: the aim of this study was to evaluate growth and survival of rainbow trout fry cultured in closed water recirculation systems (CRS). Methods: three sequential experiments were conducted, each with three CRS consisting of a fish tank, a gravel bio-filter, a water pump and aeration pumps. Fifty rainbow trout fry were placed in each system and fed with 45% protein pellets. Physicochemical and fish growth parameters were measured for each system at days 1, 15, and 30. Results: water parameters were maintained within normal values for the species in all the experiments. Observed fish growth was similar or greater than previously reported. Survival was lower, mainly due to the presence of Ich in some of the cultures. Although total biomass increase was small due to the low stocking density, condition factor and food conversion were within reported values. Conclusion: this study demonstrates that simple recirculation systems with a very small amount of water can be used for rainbow trout initiation