The use of electromyogram telemetry to estimate energy expenditure of adult fall chinook salmon

Excess energy expenditure during the upstream migration of adult fall chino ok salmon Oncorhynchas tshawytscha may reduce spawning success or lead to i ncreased prespawning mortality. Recent advances in biotelemetry make it pos sible to assess the energetic costs of upstream migration. Our objectives w ere to evaluate the use of physiological telemetry to estimate the energy e xpended by adult fall chinook salmon at different swimming velocities and t o compare these data to those associated with other species of salmonids. A n electromyogram (EMG) telemetry system was used to obtain, transmit, and r ecord an integrated EMG pulse signal that represented the time between musc le contractions. The EMG telemetry system provides a means to evaluate the effects of structural or operational changes in the hydropower system on en ergy expenditure and reproductive success of upstream migrant adult salmon. Seven adult salmon (71.5 to 106 cm fork length [FL]) were tagged and exerc ised in a respirometer at 15 and 20 degrees C. The EMG pulse rates were sim ilar between temperatures tested, but small fish (less than or equal to 90 cm FL) had a greater pulse rate than did large fish (>90 cm FL). Oxygen con sumption was related to swimming velocity, and approximately 76% of the var iance in oxygen consumption could be explained by a model that included EMG pulse rate and fish size-class designation. The results of our study showe d that adult fall chinook salmon had similar swimming performances when com pared with other salmonids, and EMG transmitters could be used to assess ac tivity rates (and oxygen consumption) in wild migrating fall chinook salmon .