title: Observations on side-swimming rainbow trout in water recirculation aquaculture systems.
abstract: During a controlled 6-month study using six replicated water recirculation aquaculture systems (WRASs), it was observed that Rainbow Trout Oncorhynchus mykiss in all WRASs exhibited a higher-than-normal prevalence of side swimming (i.e., controlled, forward swimming but with misaligned orientation such that the fish's sagittal axis is approximately parallel to the horizontal plane). To further our understanding of this abnormality, a substudy was conducted wherein side swimmers and normally swimming fish were selectively sampled from each WRAS and growth performance (length, weight), processing attributes (fillet yield, visceral index, ventrum [i.e., thickness of the ventral "belly flap"] index), blood gas and chemistry parameters, and swim bladder morphology and positioning were compared. Side swimmers were found to be significantly smaller in length and weight and had less fillet yield but higher ventrum indices. Whole-blood analyses demonstrated that, among other things, side swimmers had significantly lower whole-blood pH and higher Pco2. Side swimmers typically exhibited swim bladder malformations, although the positive predictive value of this subjective assessment was only 73%. Overall, this study found several anatomical and physiological differences between side-swimming and normally swimming Rainbow Trout. Given the reduced weight and fillet yield of market-age side swimmers, producers would benefit from additional research to reduce side-swimming prevalence in their fish stocks.
authors.affiliation: a The Conservation Fund's Freshwater Institute, 1098 Turner Road , Shepherdstown , West Virginia 25443 , USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Good
authors.forename: John
authors.initials: J
authors.lastname: Davidson
authors.forename: Christin
authors.initials: C
authors.lastname: Kinman
authors.forename: P Brett
authors.initials: PB
authors.lastname: Kenney
authors.forename: Grete
authors.initials: G
authors.lastname: Bæverfjord
authors.forename: Steven
authors.initials: S
authors.lastname: Summerfelt
mesh_terms: D000400:Air Sacs / Q000002:abnormalities* / Q000033:anatomy & histology*; D000822:Animal Husbandry / Q000379:methods*; D000818:Animals; D017756:Aquaculture; D017686:Oncorhynchus mykiss / Q000502:physiology*; D013550:Swimming / Q000502:physiology*