Adjustment of Buoyancy in Young Atlantic Salmon and Brook Trout by Changes in Swimbladder Volume

• Published in: Journal of the Fisheries Research Board of Canada
• Main Author: Saunders, Richard L.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1965
• Subjects: General Medicine; Atlantic salmon
• Online Access: http://dx.doi.org/10.1139/f65-034; http://www.nrcresearchpress.com/doi/pdf/10.1139/f65-034

The adjustment of swimbladder volume and the consequent effects on buoyancy in young Atlantic salmon and brook trout at various stages of development were measured in relation to current velocity. This was done by measuring pressure of neutral buoyancy — the pressure at which an anesthetized fish just reached neutral buoyancy as the total (atmospheric plus hydrostatic) pressure was gradually reduced — or by measuring flotation pressure — the ratio of volume of gas in the swimbladder to weight of the gas-free fish in water. Whether in static or flowing water, salmon parr were less buoyant than brook trout. Individuals of both species were more buoyant when held in still water than when held in rapidly flowing water. Adjustment in buoyancy took place when these fishes were subjected to a change in water current. Buoyancy was reduced if they were moved from still water to rapidly flowing water and was increased if they were moved from flowing to still water. Salmon smolts were more buoyant than salmon parr. This greater buoyancy of smolts is not owing to their being larger than parr. Initial filling of the swimbladder in salmon alevins can be delayed by subjecting them to strong water currents.