Managers of salmon in Lake Michigan must soon decide how many fish to put into the lake each year. The salmon fishery is a man-made industry in the Great Lakes, produced by planting millions and millions of fish in the lakes. Keeping the salmon population in balance with the food supply is a challenge these days. Some scientists are raising new questions about the salmon’s demise in Lake Huron and whether it can be stopped in Lake Michigan.
From the NYTs:
The water levels in all five Great Lakes — Superior, Michigan, Huron, Erie and Ontario — are below long-term averages and are likely to stay that way until at least March, according to the Army Corps of Engineers. (The same is true at Lake St. Clair, which straddles the border between the state of Michigan and the province of Ontario and is between Lake Huron and Lake Erie; it is not considered one of the Great Lakes, although it is part of the Great Lakes system.)
“Most environmental researchers say that low precipitation, mild winters and high evaporation, due largely to a lack of heavy ice covers to shield cold lake waters from the warmer air above, are depleting the lakes. The Great Lakes follow a natural cycle, their levels rising in the spring, peaking in the summer and reaching a low in the winter, as the evaporation rate rises.”
- Overall, drought affected 46 percent of the nation, including the Upper Midwest, where persistently dry and warmer than average conditions have helped bring Lake Superior’s water level to its lowest point on record for this time of year, according to NOAA’s Great Lakes Environmental Research Laboratory.
- Levels of all the Great Lakes, which together make up about 20 percent of the world’s fresh surface water, have been in decline since the late 1990s. Lakes Huron and Michigan were about two feet below their long-term average levels, while Lake Superior was about 20 inches off, Lake Ontario seven inches below, and Lake Erie three inches below normal in September.