After the first major dam was built near Turners Falls, Massachusetts, thirteen additional dams have ended the Connecticut River's great anadromous fish runs. Fish ladders constructed since the first fish passage in 1980 at Turners Falls, have enabled migrating fish to return to some of their former spawning grounds. In addition to dams, warm water discharges between 1978 and 1992 from Vermont Yankee Nuclear Power Plant in Vernon, Vermont released water up to degrees and the thermal plume reached downstream to Holyoke. This thermal pollution appears to be associated with an 80% decline in American shad fish numbers from 1992 to 2005 at Holyoke dam. This decline may have been exacerbated by over-fishing in the mid-Atlantic and predation from resurging striped bass populations. The nuclear plant was closed at the end of 2014, and the shad population increased.