LIMNOLOGICAL SURVEY OF WESTERN LAKE ERIE 



General Sunmaxy 

 Introduction 



^or many decades Lake Erie supported a highly nroductive commercial 

 fishery, but within the past 2$ years there has been an alarming decline in 

 oroduction of the more highly prized species, in spite of an increase of 

 fishing intensity, following the virtual collapse of the cisco fishery in 

 1925, fishermen, conservation officers, and fisheries biologists alike real- 

 ized the necessity of a scientific investigation to determine the cause or 

 cau5=es of the decline, and to determine possible remedial measures. 



A number of explanations were offered for the decrease of the catch. 

 Fishermen were persistent in their claim that pollution had made parts of 

 the lake unsijitable for fishes. Attention was directed particularly to the 

 western part of the lake because of a number of conditions which make it 

 esoecially subject to pollution, and because of its importance in the fishery. 

 The conditions which make it especially subject to pollution are: (1) the 

 presence of large industrial communities on the shores of Maumee, Raisin, 

 and Detroit Rivers, which empty into this part of the lake: (2) the extreme 

 shallowness and consequent small volume of water: (3) the presence of two 

 peninsulas and numerous islands which partially separate this area from the 

 rest of the lake, and which tend to prevent free outflow of water. The im- 

 portance of Western Lake Erie in the fishery arises from the facts that: 

 (1) large numbers of fish are caught there; (2) the area is used as a spawn- 

 ing ground by all of the commercial species except, possibly the blue pike- 

 perch. 



The Division of Conservation of the State of Ohio war the first to inves- 

 tigate the degree and extent of pollution with reference to its effect on the 

 fishery of Lake Erie. In the month of August, 1926, and in autumn and winter 

 of 1927, special parts of the lake, particularly along the Ohio shore from 

 Toledo to Cleveland, were studied. In 1926, 1929, and 1930, work was con- 

 centrated on the part of the lake west of Point Pelee. The report is based 

 principally on there^Tilts obtained in 1929 and 1930. 



The general plan cf investigation was as follows: It was assumed that 

 the offshore areas of the lake, far from sources of pollution, would be most 

 nearly normal, and that the areas near the rivers would show the maximum ef- 

 fect of pollution. Acocrdingly the lake was divided arbitrarily into five 

 sections, and parallel studies were made in each section to facilitate com- 

 parisons of the results. The offshore area, near the islands, was designated 

 the Island Section, and areas near the mouths of the four rivers studied were 

 designated the Portage River, Maumee Bay, River Raisin, and Detroit River 

 Sections. With minor exceptions the field work was done in the months of 

 April to October, inclusive. 



