302 BULLETIN OP THE BUREAU OF FISHERIES 



The principal species of commercial fish are the whitefish, trout, and herring. 

 The annual production has averaged about 15,000,000 pounds, of which the corego- 

 nids have comprised the bulk. 



Lake Michigan 



Lake Michigan is the only one of the Great Lakes that lies wholly within Ameri- 

 can jurisdiction. On the north and east its waters are controlled by the State of 

 Michigan, on the west by Wisconsin and Illinois, and at the extreme south by 

 Indiana. The lake is about 325 miles long, with an average width of 65 miles and 

 an area of about 22,000 square miles. In the lake bottom are two basins — one at 

 each end — separated in the center by an uneven stretch about 60 miles in length, 

 which bears several well-defined though yet uncharted reefs. From the south the 

 bottom slopes very gradually (at the rate of 1 or 2 fathoms to a mile) into a basin 

 with a maximum recorded depth of 97 fathoms. In this depression a somewhat cir- 

 cular area, about 40 miles in diameter, is inclosed by the 60-fathom contour. The 

 rise to the elevation in the center is rather abrupt and begins about 100 miles from 

 the southern shore. The most extensive depression extends for about 100 miles in 

 the northern half of the lake and is overlaid by 90 to 144 fathoms of water. The 

 90-fathom contour roughly outlines a triangle with the apex pointing north. For 

 about 50 miles the figure has an average width of 30 miles and then tapers rapidly. 

 So far as is known this area is not productive. The rest of the northern sector is 

 dotted with islands and reefs with conspicuous depressions between. Green Bay, 

 with an approximate area of 1,700 square miles and a maximum depth of about 20 

 fathoms, and Grand Traverse Bay, with an area of about 300 square miles and a 

 maximum depth of more than 100 fathoms, are the only extensive bays, and both 

 lie near the north end. The bottom along the shore is largely sand, but there are 

 stretches of clay and, in the north, of rock. The deeper waters overlie clay for tha 

 most part. 



The principal species are whitefish, chubs, herring, trout, perch, and suckers. 

 The annual production has been about 25,000,000 pounds, of which usually half or 

 more were coregonids. 



Lake Huron 



Lake Huron is situated in the center of the Great Lakes chain, and its waters 

 lie about equally within the jurisdiction of the Province of Ontario on the east and 

 the State of Michigan on the west. It receives the waters of Lake Superior through 

 St. Marys Kiver and those of Lake Michigan through the Straits of Mackinac. It 

 drains southward through the St. Clair River, Lake St. Clair, and the Detroit River 

 into Lake Erie. Its greatest length, from the head of the St. Clair River to the 

 Straits of Mackinac, is about 250 miles and the greatest width (near the middle) 

 about 100 miles. Excluding Georgian Bay and the North Channel, the lake has 

 an area of approximately 17,500 square miles. 



Lake Huron is divided into two approximately equal areas by the Big Reef, 

 which extends continuously from Point Clark, Ontario, to North Point, Mich. 

 North of the reef lie the deepest waters of the lake. Here the 30-fathom contour is 

 rarely more than 10 miles from shore, and a considerable portion of the area lies 

 within the 60-fathom curve. The maximum depth of 125 fathoms known in the 

 lake is found here. The southern portion is shallower. Here depths of 30 fathoms 



