Warner and Fenderson (see footnote 

 8). 



Postspray samples of fish, clams, and 

 water were taken from the four study areas 

 in 1963. The concentration of DDT and DDE 

 increased progressively in fish frona Virginia 

 Creek and Virginia Lake; in Cabin Creek 

 the values increased from June through 

 August and declined in September (table 7). 

 Fish from Old Tom and Saltery Cove Creeks 

 had only traces of DDT and DDE, and traces 

 were found also in clams and in the surface 

 and intragravel water in all four systems. 



Late in August 1963, eggs takenfrom several 

 pink and chunn salmon in Old Tonn Creek were 

 fertilized and buried in the gravel in Old 

 Tom and Cabin Creeks for 19 days to test 

 the possibility that living eggs might accu- 

 mulate DDT from the intragravel water. Sub- 

 sequent analysis showed only traces of DDT 

 and DDE. 



The final postspray observations in the four 

 streams were made from June to late August 

 1964. Emphasis of the 1964 studies was on 

 measuring the repopulation of aquatic insects 

 on test stones in the sprayed streams (Cabin 

 and Virginia Creeks), the effects of annihila- 

 tion of aquatic insects in 1963 on the condition 

 of trout, and the concentrations of DDT and 

 DDE in fish in both streams. 



The seasonal changes of abundance of 

 aquatic insects in the four streams in 1964 

 were similar to those inall the streams in 1961 

 and 1962 (figs. 2 to 5). In 1963, the seasonal 

 changes of abundance in the unsprayed streams 

 were unaccountably sonnewhat different from 

 other years (figs. 2 and 4), but the significant 

 point is that the unsprayed streanns continued 

 to support flourishing insect populations and 

 were unaffected by nearby spraying. In 1964, 

 not only had the normal seasonal changes in 

 abundance been reestablished in the test 

 strean-is, but by August the numbers had ap- 

 proached prespray levels (figs. 3 and 5). 



The DDT and DDE content of rainbow trout 

 from the control streanns. Old Tom and Saltery 

 Cove Creeks, remained at the low prespray 

 levels. Both DDT and DDE in cutthroat trout 

 from Virginia Lake and rainbow trout from 

 Cabin Creek had decreased markedly from the 

 1963 postspray concentrations (table 8), Be- 

 cause the water samples of June 1964 (table 8) 

 had only trace amounts of DDT, water analyses 

 were discontinued. 



The diet of trout in the control watersheds 

 (Old Tonn and Saltery Cove Creeks) was about 

 the sanne in 1964 as in previous years (tables 1 

 and 2 and figs. 6 and 7), and that of trout in the 

 test watersheds (Cabin and Virginia Creeks) had 

 returned to the prespray conditions of 1962. 



To determine if the drastic change in diet 

 that resulted from annihilation of the aquatic 

 insects affected the condition of the trout, 

 condition factors (K) were calciilated from 

 the formula 



Weight (grams) X lO^ 

 Fork length (millinneter s)3 



Mean values of K were determined for fish 

 collected each year fronn each study area 

 in July and August (table 9). The length- 

 frequency distribution of the fish used in the 

 calculations of condition was sinnilar every 

 year. The condition of fish generally declined 

 in the two test areas but remained nearly 

 constant in the control streanns. Although 

 Diptera and Ephenneroptera were present in 

 the test streams in normal prespray numbers 

 by August 1964 (as evidenced by counts of 

 insects on stones and in stomach sannples), 

 condition did not innprove. The condition 

 factors of trout from Cabin Creek and Virginia 

 Lake reached the lowest values of the 3 yr. in 

 1964. Fish in the test streanns nnay not have 

 had time to recover fronn the poor condition 

 resulting from a long period of food shortage 

 before they were collected in August 1964. 



Table 8. — Concentrations of DDT and DDE in water and fish from two test and two control streams 

 during 1964 field season. Prince of Wales Island, Alaska 



[Trace, < 0.005 p.p.m. in water, <0.02 p.p.m. in fish] 



12 



