PROGRESS IN BIOLOGICAL. INQUIRIES, 1922. 23 



summer and fall, the salinity of the rivers and the upper part of the 

 bay was much above normal. An apparent correlation between 

 the distribution of the mussel and salinity was found. With the ab- 

 normally high salinity, the hook mussel extended as far toward 

 fresh water as oysters occur, or a very little farther, but not to a 

 freshness equal to that which is usually to be found at the upper 

 limit of oyster's growth. In the streams it was found to extend 

 as far toward salt water as is represented by a surface density of 

 1.0121 to 1.0127. The evidence of the.se data seems strongly to indi- 

 cate that the distribution is limited to a rather short range in 

 salinity and that the presence of tjie mussels in numbers in a large 

 part of the area was made possible by the preceding dry season and 

 the consequent increase in salinity. Nothing definite was learned of 

 the cause of the remarkable abundance of the mussels. The mild 

 preceding winter and the lack of extremely strong spring freshets 

 are possible contributing factors. 



POLLUTION OF WATERS. 



During recent times no subject has been of more acute interest to 

 fishermen and dealers in fishery products than that of pollution bv 

 oils and industrial wastes. The conditions that notoriously prevail 

 in man}^ rivers and that occur, spasmodically at least, in other 

 streams and at various points of the seacoasts are proper cause for 

 concern not only to fishermen and to all interested in the fishery 

 resources, but also to consumers of water, to bathers, and to farmers 

 and other property owners. As relating to the fisheries, few sujpjects 

 are more complex and needy of special personnel and equipment for 

 effective investigation. Tliere is evidently required for the adequate 

 study of practicable means of alleviation of effects of pollutions upon 

 fisheries a special provision of funds. Although in the absence of 

 such provision the bureau has not been able to conduct continuous 

 studies of pollutions it has endeavored, as opportunities afforded and 

 means j^ermitted, to contribute to a solution of the problems involved. 

 Allusion has been made on another page (p. 13) to the special atten- 

 tion that will be given to the matter of pollutions as affecting oyster 

 culture and fisheries in Long Island Sound. 



In October and November, 1921, Carl L. Hubbs, curator of fishes in 

 the museum of zoology. University of Michigan, investigated the 

 pollution of the streams of the Saginaw water drainage in central 

 Michigan. The studies were made for the Bureau of Fisheries in 

 cooperation with the University of Michigan and the Michigan 

 Department of Health, and much of the field work was done in com- 

 pany with E. F. Badger, chemical engineer of that department. Par- 

 ticular attention was given to the several large sugar factories that 

 are located on the Saginaw River or its tributaries. Little evidence 

 was found to indicate that any definite toxic wastes are responsible 

 for the death of fishes in the streams studied ; most of the wastes are 

 of the oxygen-consuming type and kill fishes by depleting the water 

 of its natural supply of dissolved oxygen. Both sanitary sewerage 

 and the sugar-plant wastes are of this type. Below the smaller cities 

 containing sugar plants the sugar wastes are of the greater impor- 

 tance in the pollution of the streams, while on the Saginaw Eiver 



