section_path: Ecology/Fauna
section_name: Fauna
paragraph_text: Fauna
  
  While the organisms living on the bottom of shallow waters are similar to those found in smaller lakes, the deep waters contain organisms found only in deep, cold lakes of the northern latitudes. These include the delicate opossum shrimp (order mysida), the deepwater scud (a crustacean of the order amphipoda), two types of copepods, and the deepwater sculpin (a spiny, large-headed fish).
  
  The Great Lakes are an important source of fishing. Early European settlers were astounded by both the variety and quantity of fish; there were 150 different species in the Great Lakes. Throughout history, fish populations were the early indicator of the condition of the Lakes and have remained one of the key indicators even in the current era of sophisticated analyses and measuring instruments. According to the bi-national (U.S. and Canadian) resource book, The Great Lakes: An Environmental Atlas and Resource Book: "The largest Great Lakes fish harvests were recorded in 1889 and 1899 at some 67,000 tonnes (66,000 long tons; 74,000 short tons)."
  
  By 1801, the New York Legislature found it necessary to pass regulations curtailing obstructions to the natural migrations of Atlantic salmon from Lake Erie into their spawning channels. In the early 19th century, the government of Upper Canada found it necessary to introduce similar legislation prohibiting the use of weirs and nets at the mouths of Lake Ontario's tributaries. Other protective legislation was passed, but enforcement remained difficult.
  
  On both sides of the Canada–United States border, the proliferation of dams and impoundments have multiplied, necessitating more regulatory efforts. Concerns by the mid-19th century included obstructions in the rivers which prevented salmon and lake sturgeon from reaching their spawning grounds. The Wisconsin Fisheries Commission noted a reduction of roughly 25% in general fish harvests by 1875. The states have removed dams from rivers where necessary.
  
  Overfishing has been cited as a possible reason for a decrease in population of various whitefish, important because of their culinary desirability and, hence, economic consequence. Moreover, between 1879 and 1899, reported whitefish harvests declined from some 24.3 million pounds (11 million kg) to just over 9 million pounds (4 million kg). By 1900, commercial fishermen on Lake Michigan were hauling in an average of 41 million pounds of fish annually. By 1938, Wisconsin's commercial fishing operations were motorized and mechanized, generating jobs for more than 2,000 workers, and hauling 14 million pounds per year. The population of giant freshwater mussels was eliminated as the mussels were harvested for use as buttons by early Great Lakes entrepreneurs.
  
  The Great Lakes: An Environmental Atlas and Resource Book (1972) notes: "Only pockets remain of the once large commercial fishery." Water quality improvements realized during the 1970s and 1980s, combined with successful salmonid stocking programs, have enabled the growth of a large recreational fishery. The last commercial fisherman left Milwaukee in 2011 because of overfishing and anthropogenic changes to the biosphere.