Biological Survey — Erie-Niagara Watershed 137 



present/ Not only is 12 miles of what might be a valuable bass 

 stream destroyed, but the sludge deposits extend out into Lake Erie, 

 there causing a clogging of the fishing nets and undoubtedly affect- 

 ing the bottom life and fish food in that vicinity. 



Some effort was put forth this past summer to obtain further 

 information on the biological indicators of pollution. With this 

 end in view several collections of bottom forms were made in 

 Dunkirk and Buffalo harbors and the Niagara river and also 

 in the streams in the watershed. The presence or absence of any 

 particular plant or animal is not, ipso facto, an indication of the 



Seining a hole in polluted water 



condition of a body of water. There must be some few foul water 

 organisms present in fresh water before it becomes polluted or 

 they would not be present to thrive in it after pollution. Thus 

 the sludge worm, Tuhifex tuhifex, is present often in clean water 

 but it abounds under conditions of severe pollution. It is the 

 relative abundance of certain foul water organisms and the 

 scarcity of fresh water loving forms that indicate the degree of 

 pollution. 



From 31 collections of diatoms, desmicls and algae made in 

 polluted waters, over 50 forms have been identified to the genus 

 or species.^ This number will be greatly increased when the 

 difficult work of separating the many species is completed. From 

 the data obtained the species which showed the greatest abun- 

 dance throughout a particular type of pollution were selected to be 

 included in the table of indicators given on p. — : Of the 12 different 

 species of mollusks^ collected 4 are considered as indicative of 

 pollution. 



Of the total of 54 miles of stream polluted in the watershed 49 

 miles would be suitable for fishing streams. 



^ See report of Mr. Greeley, p. 164. 

 ^ Identifications by P. R. Burkholder. 



^ Identifications by Mrs. I. C. Robertson, Conchologist, Buffalo Museum of 

 Science. 



