ABSTRACT 



The use of 3-trifluormethyl-4-nitrophenol as a selective 

 toxicant to destroy sea lamprey larvae in streams tributary to 

 the Great Lakes requires that a bioassay be conducted before 

 each application. The wide geographic distribution of the 

 streams requires further that the equipment to conduct the bio- 

 assays be mobile. The necessary facilities were installed in an 

 18 -foot housetrailer shell. This equipment is described and the 

 methods for its use are outlined. Selected data from bioassays 

 in water from streams tributary to the U. S. shore of Lake Supe- 

 rior are presented and the significance of these data explained. 



