The answer to the question: The construction of which dam caused the formation of Lake Powell, would be, Glen Canyon Dam.
Explanation:
This enormous Dam, which was placed near the Colorado River, on the norther side of Arizona, started working between 1956 and 1966, and it was built by the U.S Bureau of Reclamation. The dam was built when Glen Canyon, a group of deep gorges made out of sandstone from the rock formation was flooded with water, and thus, through it, Lake Powell was also formed. Lake Powell is now one of the biggest man-made reservoirs in the United States.
Usually when a fish floats to the top of the water the fish is deceased, maybe from an imbalance in the PH levels of the water or lack of nutrition, etc. Hope this helps! let me know if i can help any further
