Table 25. --Stomach contents of IS lake trout 1 captured by angling in 1963 in Grosvenor Lake near 

 the mouth of Coville River on July 3-5 (before presmolt sockeye salmon migration) and of 21 lake 

 trout 2 captured on August 4-5 (during migration). 



Dates of 

 capture 



Stomachs 



containing 



food 



Stomachs with 

 sockeye salmon 



Sockeye salmon 

 per stomach 



Mean 



Range 



Stomachs with 

 other fish 



Me 



Other fish 

 er st omach 

 Range 



Mean 



July 3-5 

 August 4-5 



9 



21 





 21 



41 



4-167 



6 

 21 



3 0.1 

 u 6.6 



0-2 

 1-20 



! Mideye fork length range 47.0-60.9. 

 2 Mideye fork length range 46.2-58.9. 



3 Some of these were salmonlike but were too digested for positive identification. 

 4 Most of these were too digested to be identified, but many were the size of sockeye salmon 

 found in some stomachs. 



Coville River during the summer migration of pre- 

 smolt sockeye salmon from Coville Lake and are read- 

 ily taken by angling in the vicinity both before and 

 during this migration. In 1963, 39 lake trout were cap- 

 tured by angling — 18 on 3-5 July before the presmolt 

 migration and 21 on 4-5 August when many age sock- 

 eye salmon were migrating from Coville Lake. The 

 stomach contents were examined. None of the trout 

 captured on 3-5 July contained sockeye salmon and half 

 of the stomachs were empty (Table 23). In the trout 

 collected on 4 and 5 August every stomach contained 

 sockeye salmon. 



Lake trout have been observed in this area all sum- 

 mer (June to September) and it is possible that they 

 constitute a local resident population rather than being 

 fish attracted from wide areas of the lake. On 12 Au- 

 gust 1964 I fished with sport gear in Grosvenor Lake 

 near each of the four smaller stream tributaries (omit- 

 ting Hardscrabble Creek) and hooked lake trout read- 

 ily in each area. Visual observation from a slowly 

 moving boat along the shores of the south side of 

 Grosvenor Lake (the tributaries are all on the north 

 side) revealed many solitary lake trout. 



Two lake trout (both about 47 cm long) were taken 

 by angling in Grosvenor River near Grosvenor Lake 

 on 20 May 1962. These fish contained age sockeye 

 salmon, ninespine sticklebacks, and sculpins. 



I determined the length frequencies for 70 lake trout 

 collected by angling in Grosvenor Lake at the 

 mouth of Coville River and for 26 taken in gill nets 

 (about 10-cm stretch mesh) in areas C-4 and C-5 of 

 Coville Lake in 1963 (Table 24) and for 94 collected by 

 angling in Grosvenor Lake near the mouth of Coville 

 River in 1964 (Table 25). The gill nets fished in Coville 

 Lake included small mesh sizes down to those which 

 held ninespine sticklebacks and so could have cap- 

 tured smaller lake trout, which are notably absent in 

 the length frequencies. Most of the fish fell in the 45- 

 to 58-cm size range, but fish as short as 40 cm and as 

 long as 69 cm were collected. The length frequency 

 data indicate the presence of several year classes (be- 

 cause of the wide range in length and an expected slow 



growth) and the absence of the larger lake trout found 

 in some northern lakes (for example. Great Slave 

 Lake [Rawson, 1951]) and of the smaller sizes. 



Humpback Whitefish 



Humpback whitefish are widely distributed in the 



Table 24. --Length frequencies of lake trout 

 captured in Grosvenor Lake at the mouth of 

 Coville River by angling, June 22 to August 5, 

 and in units C-4 and C-5 of Coville Lake in 

 gill nets, 1 June 22 to July 20, 1963. The mid- 

 eye- fork lengths of fresh dead fish were mea- 

 sured with calipers to the nearest millimeter. 



^e net was 10-cm stretch mesh and the 

 other consisted of equal length sections of 

 different sizes: 9.5 mm, 12.7 mm, 19.0 mm, 

 22.2 mm, and 25.4 mm. About half the trout 

 were captured in the 10-cm net and the rest 

 in the smaller sizes, but the exact sizes were 

 not recorded. 



48 



