342 THE AMERICAN NATURALIST [Vol. LII ' 



if this policy should not be restricted and adjusted. One 

 or two trout hatcheries would probably be able to pro- 

 duce all of the trout needed, while the rest might be 

 turned over to the production of food fish which should 

 be placed in the larger bodies of water that support an 

 abundant aquatic plant life. The conditions in Oneida 

 Lake are in such striking contrast to those in the Adiron- 

 dacks that one can unhesitatingly suggest that this lake 

 could support an incredible number of fish. 



Intimately associated with this general problem is the 

 question of disease in fishes. Under this heading are in- 

 cluded the several forms of parasitism. Reference will 

 be made to two or three only. This is the field in which 

 the greatest progress has been made in the cure and pre- 

 vention of the diseases affecting man. But before pre- 

 vention can be applied, the life history of the parasite 

 must be understood. In the main, the work of the na- 

 tional and state governments has been confined solely to 

 hatchery problems. Here is a field that they should en- 

 ter, as many of the problems are too large and involve 

 too much expense for the individual. 

 Salmincola edwardsii (Olsson). 



This parasite belongs to the copepod group of crus- 

 taceans, many of which are familiarly known as "fish- 

 lice." Wilson says: "This family (LernaBOpodidse) of 

 parasites is widely distributed amongst fishes in both salt 

 and fresh water. Some of our best food and game fish 

 are infested with them, and when they once obtain en- 

 trance to a stock pond, fish hatchery, or aquarium they 

 usually multiply so rapidly as to become a serious 

 nuisance, and may even kill the fish" (p. 569). There 

 are some one hundred and thirty-six different species of 

 animals that belong to this family, all of which are para- 

 istic during their adult life. In the genus to which our 

 specimens belong, there are twenty species, eighteen of 

 which live exclusively upon the several kinds of trout. 



Salmincola edwardsii is found exclusively infesting the 

 brook trout (Salvelinus fontinalis). All of the specimens 



