FISHERY BULLETIN: VOL. 70, NO. I 



governing growth, the effect of increasing the 

 food supply to underyearling sockeye salmon 

 through artificial fertilization of Great Central 

 Lake, B.C., is presented here. It has already been 

 established (Parsons et al., in press; 1972) that 

 the waters of Great Central Lake are relatively 

 unproductive of sockeye salmon, the average size 

 of yearling smolts at the time of seaward migra- 

 tion being much smaller than in Babine Lake, 

 B.C. (63 mm versus 79 mm) (McDonald, 1969). 

 The average size of yearling smolts from 14 other 

 lakes in Washington, British Columbia, Alaska, 

 and Kamchatka is larger than the yearling smolts 

 from Great Central Lake (Foerster, 1968). In 

 the following account particular attention is 

 given to changes in size of juvenile sockeye salm- 

 on in Great Central Lake associated with changes 

 in their food supply prior to and after the addi- 

 tion of inorganic nutrients (see Parsons et al, 

 1972; LeBrasseur and Kennedy, 1972). 



STUDY AREA 



Great Central Lake (Figure 1) is located in 

 central Vancouver Island, British Columbia. 

 The lake is about 33 km long and varies between 

 1 and 2.5 km in width. The shoreline length is 

 72 km and the surface area is ca. 51 km^. Ele- 



vation of the lake surface is 83 m above sea level 

 and the mean depth is 200 m, with a maximum 

 depth of about 280 m. The outlet of the lake 

 runs into the Stamp River. Most of the shore- 

 line slopes very abruptly into deep water. This 

 feature is an important factor in regulating hor- 

 izontal distribution of juvenile salmon in the 

 lake, by providing a maximum amount of the 

 lake surface available to juvenile sockeye. 



LAKE SPAWNING 



A brief account of the spawning sites of the 

 sockeye salmon is presented here because the 

 location of the in-lake spawning grounds is an 

 important factor in the emergence of the alevin 

 and dispersal of the fry at the time of their initial 

 intake of food. Little or no published informa- 

 tion is available on the migration and spawning 

 of adults in the lake. Mr. F. C. Boyd of the De- 

 partment of the Environment has kindly granted 

 permission to refer to his internal manuscript 

 reports on the subject. 



Adult sockeye salmon bound for Great Central 

 Lake first enter the Stamp River as early as the 

 first week in June. This migration up the Stamp 

 River continues through June, peaks in July, and 

 in most years, ends in early August. The peak 



I2^°25 



20' 



49''25 



49° i^ 



05 



1250OO' 



I25°25' 



GREAT CENTRAL LAKE 



FISHING STATIONS 



20' 



15' 



10' 



49°25 



49°20' 



05' 



I25''00 



Figure 1. — Great Central Lake showing the six fishing stations and depth contours in meters. 



38 



