CALCIUM-ION - ODORANT FOR NATURAL-WATER DISCRIMINATIONS AND MIGRATORY BEHAVIOR OF SOCKEYE SALMON

1. Physiological and behavioral experiments demonstrate an acute sensitivity of the olfactory system of sockeye salmon (Oncorhynchus nerka) to calcium ions. 2. Gross-potential (olfactory EEG) responses were reliably elicited by calcium at 5 × 10-6 M (a concentration well below the range found in natural fresh waters) and most animals responded differentially to calcium concentrations throughout the natural water range. 3. Mitral cell and granule layer cells of the olfactory bulbs responded to concentrations as low as 1 × 10-6 M CaCl2. Responses in each case were ion-specific. 4. In addition, behavioral experiments demonstrated that unconditioned sockeye fry would discriminate between 2 natural waters that differed only in calcium concentration (Table 1). 5. It is proposed that salmon recognize individual natural waters on the basis of the characteristic combination of odorants present and that calcium is one of these important odorant components. 6. The fact that large synchronous wave EEG responses induced by natural waters following distilled water are largely attributable to the calcium ions present (Fig. 7) may be important for the interpretation of earlier EEG studies of salmon homing. © 1978 Springer-Verlag.