Role of Olfaction in the Behavioral and Neuronal Responses of Atlantic Salmon, Salmo salar , to Hydrographic Stratification

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Døving, Kjell B., Westerberg, Håkan, Johnsen, Peter B.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1985
• Subjects: Aquatic Science; Ecology, Evolution, Behavior and Systematics; Atlantic salmon; Salmo salar
• Online Access: http://dx.doi.org/10.1139/f85-207; http://www.nrcresearchpress.com/doi/pdf/10.1139/f85-207

The behavior of sham-operated and anosmic Atlantic salmon, Salmo salar, was studied in a fjord system with close reference to the fine-scale hydrographic features. Control fish made small-amplitude vertical movements, with sudden large-amplitude excursions. The anosmic fish made large continuous searches up and down in the water column, descended below the sill depth of the fjord, and followed the bottom contours. None of these three behaviors was seen in the control fish. The trauma caused by the surgical incision did not prevent the fish from active swimming, and a fish with unilateral sectioning of the olfactory nerve returned to the river of release. Activity of single olfactory bulb neurons was recorded during stimulation of salmon olfactory epithelium with water samples taken from different depths of the fjord. These water samples had been taken from regions that showed layering and to which migrating salmon demonstrated behavioral preferences in ultrasonic tracking experiments. Ninety percent of responding neurons showed differencial responses to the water samples, indicating the capacity of the olfactory system to discriminate among stratified water layers found in the ocean. We conclude that olfactory discrimination of fine-scale hydrographic features may provide a necessary reference system for successful orientation in nearshore regions by salmon.