An experimental tank used in a thermal challenge experiment for adult salmonids

An experimental tank used in a thermal challenge experiment for adult salmonids. The upper lobe of an adult Chinook salmon (Oncorhynchus tshawytscha) caudal fin is visible in the center of the water surface. The blue cylinder in the water on the right side of the tank is the primary propane heat source to warm river water to experimental temperature. Additional electric heaters for maintaining consistent experimental temperature are suspended in the water from the perforated crossbars attached to the tank rim. Electronic controls are covered by the white plastic bag in the background as a precaution against moisture from the circulation pump spraying water back into the tank for oxygenation. Photo taken in June 2018, Pilot Station, Alaska, USA.