Short Term Exposure of Migratory Coho Salmon Oncorhynchus kisutch to Increased CO2 Concentrations Impairs Olfactory Sensitivity to Homing Cues

The present study was conducted to examine the effects of elevated CO2 concentrations on coho salmon’s olfactory sensitivity to homing cues during migration. Migratory coho salmon were treated with ambient (450 ppm) and elevated CO2 (1500 ppm) tensions for two weeks. Two choice maze experiments were performed to evaluate their preference for control water and 5% hatchery water containing homing cues. Then the staying time and frequency to visit either side of the channel were measured. The control fish group displayed preference to the homing cues (staying time: 683.50±187.60 sec, frequency: 5.50±2.16) over control water (staying time: 22.67±16.81 sec, frequency: 0.83±0.54). However, the fish group treated with 1500ppm CO2 tension did not display preference behavior to 5% hatchery water (staying time: 354.83±192.88 sec, frequency: 2.17±1.33) compared to control water (staying time: 268.00±190.98 sec, frequency: 1.17±0.60). Results from the present study indicate that short term exposure to elevated CO2 concentrations can impair migratory salmon’s olfactory sensitivity, with the potential to disrupt homing migration. Further studies on physiological and molecular mechanisms underlying CO2 induced olfactory impairment are underway.