18 ^ U, S. BUREAU OF FISHERIES. 



fisheries steamer Fish Flawk^ and observations were taken at 29i) 

 stations. 



Although at tlie end of the fiscal year the work was not completed. 

 Doctor Galtsoff was able to make an interesting progress report. 

 The Sound receives salt water through both ends, but by far the most, 

 probably nine-tenths or more, enters through the east end known 

 as the " race." The entering sea water is diluted by the discharge 

 from numerous rivers, particularly on the north shore, so that there 

 is a marked decrease in salinity from the race tO' the head of the 

 Sound. There is also a seasonal variation. From July to November 

 the salinity rose and thereafter it gradually decreased. Highly 

 polluted water enters from East River and from many industrialized 

 and sewage-polluted streams and harbors. Accordingly, at the head 

 of the Sound the bacterial content was high, up to 4,000 per cubic 

 centimeter, and in certain harbors very high, indeed, up to 20,000 

 per cubic centimeter. However, so great is the dilution in the Sound 

 that within 2 or 3 miles off the mouths of the worst polluted harbors 

 the bacterial content was reduced to 100 per cubic centimeter or less. 

 Corresponding Avith the evidences of pollution afi'orded by the bac- 

 terial examinations, the dissolved oxygen content was low at the head 

 of the Sound and in the harbors but fairly high a short distance aw^ay 

 from these polluted areas. 



Being less affected by ocean conditions, the waters of the western 

 part of the Sound show much higher summer temperatures than 

 were found at the mouth. An increase also occurs in inshore watei's. 

 The hydrogen-ion studies revealed comparatively little variation 

 from place to place, daj- to day, or season to season. Except for the 

 one river, the pH values for the Sound and estuaries ranged only 

 from 8 to 8.3. In the Housatonic River, which receives an extreme 

 amount of acid pollution, values of 7.6 and 7.8 were recorded. Much 

 of this information is of great interest in the study of the oyster- 

 cultural problems of the region. When the examination of the ma- 

 terial is completed and the work of another year added, a fine basis 

 for the study of specific problems will have been laid. 



STUDIES or MARINE PLANKTON IN RELATION TO THE FISHERIES. 



During the past year an investigation of the seasonal variation in 

 the plankton of the Woods Hole region was carried on by Dr. 

 Charles J. Fish, assisted by Marie D. P. Fish. The jDurpcse of the 

 work was to make an exhaustive investigation of the planlrton, the 

 seasonal variation of the various species, their interrelationships, 

 and. the general factors governing their distribution. As plank- 

 tonic organisms form the sole food of the pelagic larval fish and are 

 important factors, both directly and indirectly, in the diet of the 

 adults, the results of the present investigation will serve as a basis 

 for a future study of the factore governing the seasonal variation 

 of both the fry and the adult fishes. 



Examinations of collections taken daily were made throughout 

 the year, together with records of temperature, salinity, and other 

 physical governing factors. The seasonal variation of 291 species 

 of plankton organisms, of which 36 were larval fish, were recorded. 

 It was found that salinity has little or no effect on the plankton of 

 the immediate region. No fresh-water streams of any size enter 



