Table 3. — Nunber of insects and other organisms per square foot 

 {0.092m. ^) collected in riffle areas in Wilson Q7eek before chem- 

 ical treatment and 1 week after treatment, and on the same dates 

 the Little Garlic River (untreated control), Lake Superior, 1964- 



Insects: 

 Plecoptera 



Perlidae 



Chloroperlidae. . 

 I^hemeroptera 



Ephemeridae 



Caenidae 



JJihemerellidae. . 



Heptageniidae. . . 



Leptophlebiidae. 



Baetidae 



Oionata 



Gontphidae 



Megaloptera 



Sialidae 



Trichoptera 



Hhyacophilidae. . 



Philopotamidae. . 



Psychomyiidae. . . 



Ifydropsychidae. . 



Leptoceridae. . . . 



Brachycentridae. 

 Coleoptera 



ELmidae 



Diptera 



Tipulidae 



Simuliidae 



Chirt '".jmidae. . . . 



Heleidae 



Tabanidae 



Rhagionidae 



Bnpididae 



Muscidae 



Other invertebrates : 



Annelida 



Crustacea 



Isopoda 



Hydracarina 



Mollusca 



Gastropoda 



Wilson Creek 



Pretreatment 1 week 



Little Garlic River 



. Pretreatment 1 week 



Number per square foot 



Three Mile Creek was treated with a mix- 

 ture of TFM and Bayluscide. Samples were 

 taken in riffle areas 1 day before treatment, 

 and 1 week and 6 weeks after treatment; on 

 the same dates riffle areas of Little Scarboro 

 Creek were sampled as a control. The total 

 number of organisms had not changed greatly 

 in Three Mile Creek 1 week after treatment, 

 but the number of Psychomyiidae, Chiro- 

 nomidae, and Amphipoda had declined (table 

 4). If Elmidae had not increased greatly 1 

 week after treatment, the total number of 

 organisms would have been 69 percent of the 

 pretreatment count. Without the large influx 

 of Baetidae 6 weeks after treatment, the total 

 count would have been 117 percent of the 

 pretreatment number. No major adverse effect 

 of the use of TFM or of Bayluscide as a 

 synergist with TFM can be seen; indeed, in- 

 creases in numbers of organisms were rela- 

 tively greater in the treated than in the con- 

 trol stream. 



The increase in total number of organisnns 

 in Little Scarboro Creek, the control stream, 

 after 1 and 6 weeks (table 4) was brought 

 about largely by Elnnidae, as in Three Mile 



Creek. Trichoptera declined 65 percent in the 

 treated stream and increased 49 percent in the 

 control 1 week after treatment, although the 

 Hydropsychidae, the only family that was well 

 represented in this series, showed little change 

 in either strean-i. Chironomidae declined in 

 both the treated and control streams. 



Changes in Riffle and Sand-Detritus Areas 



Two habitats were sampled in the Iron River; 

 one was an area of sand, detritus, and water- 

 weed ( Anacharis sp .) and the other a riffle. 

 Posttreatnnent samples were taken 1 week 

 after exposure at each location and 1 year 

 later in the riffle area (table 5). 



One week after treatment of the Iron River, 

 the total nunnber of organisms was 64 percent 

 of the pretreatment number in the riffle area 

 and 51 percent in the sand-detritus area. The 

 76 percent decline of Trichoptera in the riffle 

 area was similar to the declines in Wilson 

 Creek and Three Mile Creek. Other aquatic 

 insects that declined were Caenidae, Elmidae, 

 and Chirononnidae in the riffle and Caenidae, 

 Elmidae, Dytiscidae, and Heleidae in the 

 sand-detritus area. Among the other organisms 

 that were represented, Cladocera, Amphipoda, 

 and Hydracarina were reduced in the sand- 

 detritus area, and Pelecypoda in the riffle 

 area. The sample taken 1 year after treatment 

 in the riffle area showed good recovery of 

 most groups; the total of all organisms was 

 108 percent of the pretreatment number. 



Collections were made at five locations on 

 the Sturgeon River 1 day before, and 1 week, 

 6 weeks, and 1 year after treatment. The three 

 upstream stations were in areas of sand and 

 detritus, and the two lower stations were in 

 riffles (table 1). The greatest reduction in 

 number of organisms (to 25 percent of the 

 pretreatment number) came 1 week after 

 treatment in the upstream sand and detritus 

 areas (table 6) where concentrations of TFM 

 were higher than in riffles (table Z). The total 

 number of organisms was 65 percent of the 

 pretreatment number in the riffle areas. 

 Some of the same groups that declined in the 

 Iron River also declined in this stream; nannely, 

 Caenidae, Heleidae, and Hydracarina in the 

 sand and detritus areas, and Elmidae in riffles. 

 After 6 weeks invertebrate populations had 

 recovered to 101 percent of the pretreatment 

 number in the riffle areas but were only 56 

 percent of the pretreatment abundance in the 

 more heavily depleted sand and detritus areas. 

 The number of organisms had recovered 

 fully in both areas after 1 year. 



Gongeau Creek was sampled in a sand and 

 detritus area 1 day before, and 1 week and 6 

 weeks after treatment. For all groups of 

 aquatic invertebrates taken in sand and detritus 

 areas of Gongeau Creek numbers were fewer 

 1 week after treatment than before treatment 



