Section Page 



4 Schematic diagram of the environmental hazard evalua- 

 tion process 55 



6 Commercial production of lake trout in Lake Michigan .... 76 



6 Mortality of fry of Lake Michigan lake trout exposed to 



DDE and PCBs at concentrations simulating those found 

 in water and plankton of Lake Michigan and at concen- 

 trations 5 and 25 times higher 81 



7 Acetycholinesterase in nervous ganglia of molluscs with 



varying resistance to Dylox 88 



7 Inhibition by Dylox of acetycholinesterase in nervous 



ganglia of Limnaea stagnalis and Planorbis corneas .... 89 



7 Change in the activity of acetylcholinesterase in perch 



brain after exposure to Dylox 91 



7 Densitograms of the molecular form of acetylcholine- 



sterase in carp and the snail unexposed and exposed 



to Dylox 92 



8 Map of the United States illustrating the National 



Pesticide Monitoring Program stations where freshwater 



fish are collected for routine contaminants analyses . . . 100 



8 Geometric mean total DDT residues in freshwater fish, 



1969-1976/77 104 



8 Percent occurrences of polychlorinated biphenyl (PCB) 



residues in freshwater fish, 1976/77 108 



8 Occurrence of toxaphene residues exceeding 1.0 mg/kg in 



freshwater fish (1976-1977) 109 



10 Effect of prior ammonia acclimation on the acute toxicity 



of ammonia to rainbow trout 123 



10 Effect of reduced temperature on the acute toxicity of 



ammonia to fathead minnows 125 



10 Acute toxicity of ammonia vs. temperature for fathead 



minnows 126 



10 Effect of dissolved oxygen on the acute toxicity of 



ammonia to fathead minnows and rainbow trout 128 



