food by rooting about in the mud (Cole, 1905, p. 567), and presumably 

 it would ingest the worms, although Cole did not list tubificids as 

 an item of food in the carp of Lake Erie. Stewart (1926, p. l8o) 

 pointed out that the adult sucker ( Catostomus commersonii ) holds large 

 food particles in the mouth and rejects the sand before swallowing. 

 Such a habit would result in the loss of many small organisms like the 

 tubificid worms. Other bottom feeders such as the perch, catfish, and 

 sheepshead are also more discriminating in their food habits than the 

 carp and might profit little from the presence of the worms. The 

 whitefish need not be considered in this connection because it is 

 present in this area of the lake only during the spawning period, when 

 it takes little or no food. 



On the whole it seems probable that, even though the 

 tubificids are not used to a great extent, the sphaeriid and other 

 molluscs are abundant enought on polluted bottom to prevent a food 

 shortage for the bottom-feeding fish. 



Wide acceptance has been given to the idea that the decline 

 of the whitefish (Coregonus clupeaformis) has resulted from pollution of 

 its spawning grounds. Formerly the whitefish was extremely plentiful 

 in Lake Erie. It spent most of the year in the deeper water east of 

 the islands, but in autumn migrated westward to spawn. Large numbers 

 entered Detroit River to spawn in the river, in Lake St. Clair, and 

 even in St. Clair River. For many years the v^itefish has not entered 

 Detroit River in commercial quantities, VJithin recent years the 

 Federal hatchery at Put-in-Day has been unable to get sufficient eggs 

 along the west shore of the lake to fill the hatchery. The fact that 

 considerable numbers still ^awn in the vicinity of the island makes 

 the case against pollution a strong one. However, other possible ex- 

 planations present themselves. 



Rapid decrease in the abundance of whitefish in the Great Lakes 

 had been noted prior to I870 (Milner, 187U) , In the last decade of the 

 centurj'- the decline of the Lake Erie whitefish had become alarming. 

 The fishery of Detroit River, described by Milner as highly successful, 

 had been abandoned (Rathbbun and Wakeham, l897, p, II6) , These writers 

 mentioned the possible effect of sewage pollution on the river fishery, 

 but expressed the opinion that overfishing, both in the river and in the 

 lake below it, was the principal factor involved (p. II6 and pp. 101 - 

 102), This suggests the possibility that there are distinct strains or 

 races of whitefish, and that the one which formerly spawned on the west 



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