Several hundred specimens from laboratory tests, or from areas treated 

 for eradication of imported fire ants, have been analyzed to determine distri- 

 bution of insecticides in tissues following varying degrees of exposure. 

 Although only a few representatives of some species have been examined, it 

 appears that the quantity stored varies from compound to compound and from 

 species to species (Tables 10, 11 and 12). 



Laboratory tests with rainbow trout are beginning at the Bureau's Fish- 

 Pesticide Research Laboratory in Denver, Colorado, to measure acute toxicity 

 resulting from exposure to common insecticides, and to understand the influ- 

 ence on toxicity of size, sex, physical condition, dosage rate, water chemis- 

 try, and other factors in the environment. 



Chemical analyses for toxaphene in fish from Clayton Lake, New Mexico, 

 have been made in the Denver laboratories. The resulting data, as well as DDT 

 analyses from fish exposed in the Yellowstone River, show great variation from 

 fish to fish in the amounts retained in the tissues. However, fish show a 

 steady statistically significant increase in toxaphene concentration with time 

 of exposure (Cope, unpubl.). Residues of DDT were highest in adipose tissue} 

 all fish collected had DDT in their bodies (lO). 



IV. DIRECT EFFECTS OF PESTICIDES ON FIELD POPULATIONS 



Direct intoxication in the field is correlated with the particular habi- 

 tat, chemical, dosage rate, formulation, species involved, and a host of other 

 ecological considerations. 



A. Forest Insect Control 



Forest insect programs using a pound of DDT or less per acre have covered 

 about 20 million acres in the United States, but have not produced serious 

 widespread immediate die-offs of terrestrial forest vertebrates. In local 

 areas where operational control was faulty and dosages were considerably 

 higher than intended, mortality has been evident. However, some invertebrates, 

 which constitute important foods for many vertebrates, are seriously reduced 

 in numbers during these applications, and losses of aquatic organisms result 

 when water environments are contaminated. 



Two recent serious die-offs of fish have emphasized the importance of 

 keeping the pesticide from aquatic habitats. The first was the Miramichi 

 River in New Brunswick, Canada. In 1954, a treatment of 0.5 pound of DDT per 

 acre to control spruce budworm resulted in the loss of up to 913^ of the young 

 Atlantic salmon of three age groups and some adults in the treated area [35], 

 [37]. 



Portions of the Miramichi River drainage were treated again in 1956 and 

 1957, with very much the same results as in 1954 [34], [36]. These repetitive 

 treatments (5 million acres in 1957) have largely undone the fish restoration 

 activities of the aquatic biologists who predict a decline in the salmon runs 



[34]. 



