RIVER TEMPERATURE VARIATIONS AND POTENTIAL EFFECTS ON FISH IN A TYPICAL YANGTZE RIVER REACH: IMPLICATIONS FOR MANAGEMENT

Operation of large reservoirs often alters the water temperature regimes in downstream reaches. Water temperature, a key environmental factor, affects the reproduction, growth, and distribution of most riverine fishes. This study reveals water temperature variations in the Yichang reach of the middle Yangtze River during 1956-2014 and the potential effects on the reproductive timing of the four major Chinese carp and Chinese sturgeon, Acipenser sinensis. Our results indicate that: 1) water temperature increased significantly in winters in the past 59 years and declined during spring in this century; 2) construction and operation of the Three Gorges Reservoirs has significantly altered the water temperature regime, i.e., delayed suitable spawning temperature; 3) changes in the water temperature regime have significantly affected the reproduction season of the four major Chinese carps and Chinese sturgeon in the reach. This study will be beneficial for national and local agencies developing adaptive management strategies, including mitigation measures in the face of increased hydropower station growth in the Yangtze River.