The Plankton Algae of the Palisades Interstate Park 133 



that the algae surviving the treatment would develop a strain resistant 

 to copper sulphace in small quantities has not been realized, and algae 

 yield to treatment in reservoirs where the method of eradication has 

 been practiced since it was discovered twenty years ago. 



EFFECT OF THE COPPER SULPHATE TREATMENT ON FISH 



The plan for the recreational and educational development of the 

 Palisades Interstate Park includes the cultivation of fish in its ponds 

 and lakes, in order to increase their utility and the recreational pos- 

 sibilities of the Park. A preliminary report on a general fish cultural 

 policy for the Park has been published (Adams, Hankinson and 

 Kendall, '19) based on field studies during the summers of 1918 and 

 1919. 



The superabundance of algae, particularly in ponds abounding 

 in decaying plant remains (as in Carr Pond) has been given as the 

 cause for the death of fish. Among the records of the sudden dying 

 of fish where it is ascribed to algae are the observations of Haine 

 ('18), Hyams and Richards ('01), Baldwin and Whipple ('06) and 

 an anonymous report in the Bulletin of the New York Zoological 

 Society ('13). The investigations of Baldwin and Whipple were 

 the most complete and they show that while the algae killed the fish 

 they did not poison them directly, but that the death of the algae 

 following their blooming caused an exhaustion of the oxygen supply, 

 which, in turn, caused the death of the fish. That this death of fish 

 in connection with a blooming of the pond is due to the exhaustion 

 of the oxygen is borne out by the observations of Haine ('18), who 

 shows that when algae have been killed by copper sulphate there is a 

 sharp decrease in the oxygen content of the water following such 

 treatment, due to the bacterial oxidation of the dead algae, and that 

 this oxygen reduction may afifect the fish. 



The question of the eflfect of copper sulphate upon fish as well ay 

 upon algae is of great importance. This question was raised soon 

 after the introduction of Moore and Kellerman's method, especially 

 in its application to aquaria and fish cultural waters. A more recent 

 use of copper sulphate is in the application of it in sufficient quanti- 

 ties to kill undesirable fish before restocking with certain game fish 

 (Titcomb, '14). When these different points of view are taken into 

 consideration we have a greater knowledge of the reaction to this 

 compound than might be expected, although attention should be 

 called to the fact that any particular species of fish shows a greater 

 range of susceptibility in different sections of the country than do the 

 algae. This may be due to the fact that there are physiological dif- 

 ferences between species of fish in different localities, even when fish 

 from different localities appear to be identical. This indicates that 

 local investigations must be made the basis of practical remedial 

 work. Fortunately fish are less susceptible than algae and, although 

 the toxic limits of the two frequently approach, it is often possible to 

 eradicate algae without seriously harming the fish. The followins^ 

 table shows the reported responses of fish to different concentrations 

 of copper sulphate. 



