Plankton was obtained fronn the ocean in 

 the vicinity of each study area before and 

 after the spraying. A plankton net about 

 45.7 cm. in diameter (No. 20 nnesh) was 

 towed behind a boat at a depth of about 

 1.2 m. The san-iples were put in quart jars-- 

 about one-half quart of plankton and the 

 rest sea water. They were frozen and later 

 analyzed for DDT. 



INSECTICIDE APPLICATION 



DDT was applied to the test watersheds, 

 Virginia and Cabin Creeks, at 0.28 kg. per 

 hectare. Fuel oil was used as a vehicle, and 

 the mixture was sprayed from an airplane. 

 No attempt was made to avoid spraying the 

 streanns. 



The plan was to spray both watersheds the 

 same day. Spraying began on Virginia Creek 

 on June 18, 1963, but was halted when high 

 winds arose, after only one-third of the 

 watershed had been covered. The rest of the 

 Virginia Creek watershed and all of the Cabin 

 Creek watershed were sprayed under ideal 

 conditions on June 21, 1963. Technical details 

 of the application, not pertinent to this report, 

 are described in a report by the Forest Serv- 



INSECTICIDE ANALYSES 



Samples of water, fish, clams, and plankton 

 were sent to the Wisconsin Alumni Research 

 Foundation for analyses of DDT and its bio- 

 logical derivative DDE. The early analyses 

 were by paper chromatography and the later 

 ones by electron-capture gas chronnatography. 

 The concentrations of insecticides were ex- 

 pressed in parts per nnillion. The lower 

 linnits of reliable sensitivity of analytical 

 procedure were 0.005 p. p.m. for DDT in the 

 water samples and 0.002 p. p.m. for DDT 

 and DDE in fish (whole), clams (excluding 

 shells), and plankton. 



PRESPRAY OBSERVATIONS 



Prespray observations in the study areas 

 from August 1961 to mid- June 1963 estab- 

 lished normal levels and seasonal variation 

 of abundance of aquatic insects, diet of trout, 

 and concentrations of DDT in water, fish, 

 clams, and plankton. The numbers of insects 

 drifting downstream were sampled a few 

 days before spraying and on the day of spray- 

 ing. 



^ U.S. Forest Serv. Skowl Arm DDT pilot project, 46 p. 

 On file Forest Serv., Reg. 10, Juneau, Alaska. 



The average abundance of Diptera and 

 Ephemeroptera on test stones at weekly inter- 

 vals during the summers are shown in figures 

 2 to 5. In all four streams abundance normally 

 increased from low levels in early June to a 

 high in late July and early August and then 

 declined gradually to early September (except 

 in Saltery Cove Creek in 1963). Samples of 

 the larvae of aquatic insects from test stones 

 were identified to genus. The four most abun- 

 dant orders and the genera of each were: 

 (1) Plecoptera: Arcynopteryx , Hastaperla , 

 Claassenia , and Acroneuria ; (2) Ephemerop- 

 tera; Cinygmula , Iron , Anepeorus , Ameletus , 

 Paraleptophlebia , Ephemerella , Baetis , and 

 Apobaetis ; (3) Trichoptera: Glossosoma , 

 Chimarra, and Ochrotrichia ; (4) Diptera: 

 Tipula , Dixa, Simulium , and Dolichopus . 



Drifting aquatic insects were sampled for 

 three 5-min. periods in each of the four 

 streams on June 16, 1963, a few days before 

 spraying. Only Diptera were caught in the 

 nets-- 10 in Virginia Creek, 7 in Old Tom 

 Creek, 4 in Cabin Creek, and none in Saltery 

 Cove Creek. 



Rainbow trout were collected in Old Tom, 

 Cabin, and Saltery Cove Creeks and cutthroat 

 trout in Virginia Lake in July 1962 to study 

 the normal diet. The contents of the stomachs 

 of fish collected from the four systems are 

 presented graphically by major groupings in 

 figures 6 and 7 and in more detail in tables 

 1 and 2. For comparative purposes, the figures 

 and tables give both prespray (1962) and 

 postspray (1963 and 1964) data. The normal 

 diet contained about 25 to 50 percent aquatic 

 insects by volume. The "debris" category 

 was composed principally of sand and bits 

 of leaves and twigs. 



I could find no record of any earlier large- 

 scale use of chemical insecticides on Prince 

 of Wales Island; therefore, I did not expect 

 to find DDT in water samples collected before 

 the test spraying of this program. Yet the 

 samples of water collected in 1961 from the 

 Cabin Creek watershed contained an unusually 

 high level of DDT for an unsprayed area 

 (table 3). I made a thorough but unsuccessful 

 search for clues as to the source of the con- 

 tamination. The validity of the DDT deter- 

 minations made in 1961 was supported by the 

 analyses of fish collected in 1962--fish sampled 

 from Cabin Creek and Virginia Lake contained 

 concentrations of DDT and DDE greater than 

 usual for an unsprayed area, though normal 

 levels existed in Old Tom and Saltery Cove 

 Creeks (table 3). The concentrations of DDT 

 and DDE in water, fish, clan-is, and plankton 

 were normal in all the study areas in June 

 1963 before spraying. 



The prespray data thus established the 

 normal summer abundance of aquatic Diptera 

 and Ephemeroptera in the streams, the diet 

 of the fish, and the prespray levels of DDT 

 in water, clams, plankton, and fish. 



