TABLE 15. — Parasites and their hosts found in catches of fish from Brooks Lake, 1957 



Juvenile Adult ^^^^^^^ ^ake Dolly , , . Stickle- 

 sockeye sockeye ^^^^^ ^^^^^ ^^^^^ Sculpins ^^^^^ 

 salmon salmon 



■"■ Mature forms in sockeye salmon and immature forms in sculpins and sticklebacks . 

 ^ Lake trout stomachs contained immature and adult forms. 



that they acquire the parasite after entering 

 the lake and that infestation is very rapid. There 

 were no apparent effects from these ecto- 

 parasites, and they probably do little harm. 

 Infestations were heaviest during July and 

 diminished in August and September. 



Sculpins and sticklebacks were often heavily 

 infested with trematode cysts and the trema- 

 tode Schistocephalus solidus. 



Lake trout were t le most heavily parasitized 

 fish in Brooks Lak , most commonly by the 

 cestode Eubothnum ip., but also by Salmincola 

 and TriaenophoTus. These same parasites are 

 characteristic in lake trout of Great Bear Lake 

 (Miller and Kennedy, 1946). The large heads 

 and thin, emaciated bodies of the trout were 

 evidence of the infestation. 



The occurrence of plerocercoids of 

 Dibothriocephalus latus in sockeye salmon and 

 rainbow trout was expected because adults 

 of this parasite were often observed in bear 

 feces in streams where bears fed on salmon. 



Probably parasites have little effect on 

 sockeye salmon in Brooks Lake, except bene- 

 ficially in possibly limiting the predatory lake 

 trout population. 



SCUBA 



SCUBA has been used with considerable 

 success in fish behavior research in relatively 

 warm tropical and temperate waters wherever 

 transparency is high enough to permit good 

 visibility. A limited trial was made at Brooks 

 Lake in 1957 to evaluate its potential in ob- 

 serving, in cold water, the distribution and 

 behavior of sockeye salmon during their 

 lacustrine life. Equipment included the follow- 

 ing: compressed air tanks and regulator, 

 rubber dry suit with hood and gloves, long 

 wool underwear, wool socks, swim fins, face 

 mask, and safety line. 



On the afternoon of August 3, three dives 

 were made in calm water under an overcast 

 sky. Figure 26 shows the diver preparing to 

 dive. His verbatim description of each dive 

 follows: 



Dive 1 — Dive was of 10 minute's duration 

 and extended from station I in 5 to 6 meters 

 of water 100 yards south along the bottom, 

 which was completely covered with a mat of 

 vegetation. No fish were observed. 



Dive 2 — Dive was made in immediate 

 vicinity of station II over 120 feet of water. 



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