50 TJ. S. BUREAU OF FISHERIES. 



On Jul}'^ 10 and 11 the obstructions were removed and most of the 

 choked area (D 1) opened to fishes. On the hitter day large numbers 

 of mud minnows and common sunfishes had entered these waters. 

 Most of the hitter, which were very numerous, were yearling fish 

 from 2 to 3 inches long. Of the stomachs of 10 examined (Table 7, 

 No. 2331, p. 41) mosquito larvae were detected in four, the remaining 

 food being of the mixed character found in fishes taken outside of this 

 area and consisting chiefly of chironomid larvoe with some other 

 insects, mollusks, minute crustaceans, and a small amount of plant 

 remains. 



The rate of breeding in different parts of this area on July 10 

 averaged from 16 to 60 per 10 samples at each j)oint, or 32 for the 

 entire area. 



On July 15 the rate of breeding had fallen greatly in all places 

 accessible to the fishes but remained undiminished where still barred 

 to them. 



The area was next seined on July 24, when large numbers of sun- 

 fishes were taken close inshore throughout the experimental area. 

 Of seven (Table 7, No. 2360a, b) examined, mosquito larvte and 

 pupae were detected in three, and in one of these were several. The 

 breeding rate had fallen to an average of below 4 for the opened 

 area, while in unaltered checks, natural cut-off pools, and pens it 

 averaged 28, including some pupse of both Culex pipiens and Aedes 

 sylvestris. 



On July 30 only an occasional mosquito la;rva could be found in 

 the opened waters while in the checks the rate was undiminished. 

 Of 3 stomachs of sunfishes (Table 7, No. 2364b) taken here which 

 were examined 1 contained 3 Culex pipiens larvse. 



On August 23 breeding averaged 1 larva to 5 dippers except in an 

 occasional sheltered spot where <&g^ boats or newly hatched larvae 

 were found. In the latter case counts ran as high as 6 per dipper. 

 In the checks the averages for each ran from 8 to 20 larvre and 

 pupaa in addition to many Q^g boats. On this date, of 13 stomachs 

 (Table 7, Nos. 2377a and 2377b) examined, only 2 contained mosquito 

 larvae, showing a falling off in their use as food as their numbers 

 diminish. 



Similar treatment was given to a shallow bay (fig. 1) at Globe 

 Camp (J 3) on Car Pond. This exceeds 500 feet in length and 

 averages 300 feet w^ide. At its head and along its eastern side was 

 a heavy growth of emergent vegetation, chiefly grasses, while in the 

 open water just oft' the shore was a dense barrier of Ceratophyllum 

 and Utricuhiria. Along this side and about the head a low rocky 

 shore was favorable to the formation of many small pools isohited by 

 rocks and other barriers from the open Avaters (fig. 4). When first ex- 

 amined on July 7, 1919, an area exceeding an acre was badly choked 

 with driftwood and debris in addition to the vegetation. In this 

 stagnant area Utricuhiria, Lemna, and filamentous algae were groov- 

 ing luxuriantly, the water was somewhat contaminated by kitchen 

 drainage from one of the camps, and conditions were ideal for 

 breeding of Culex pipiens. Large numbers of the larvae and ^gg 

 boats of this species were found not only in the choked part of the 

 bay, but also associated with Aedes sylvestns, especially in the iso- 

 lated pools (40-|- per sample). Fishes (mud minnows, common sun- 



