This study evaluated the use of vertically-suspended structure as a form of environmental enrichment during hatchery rearing of rainbow trout Oncorhynchus mykiss. This experiment was broken up into two rearing periods, with fish remaining in the same treatment throughout the study. The first period began with initial feeding and lasted for 48 days. The second commenced immediately after the first and lasted for 132 days. At the end of the first period, final tank weight, gain, and feed conversion ratio were not significantly different between the tanks of fish with or without vertically-suspended structure. At the end of the second period, final tank weight and gain were significantly greater in tanks with vertically-suspended environmental enrichment compared to the unenriched control tanks. Condition factor was also significantly higher in the fish reared with structure. The results of this study indicate that vertically-suspended environmental enrichment use is not harmful during the period of rainbow trout initial feeding and positive impacts on growth occur at the later stages of juvenile rearing.
Benj Morris, Nathan Huysman, Eric Krebs, Jill M. Voorhees, and Michael E. Barnes