CONTENTS 



Page 



Introduction 1 



The study area 2 



Methods and equipment 4 



Sampling units 4 



Types of gear 4 



Measurements of fish 5 



General distribution and abundance of all fish species 6 



Abundance of juvenile sockeye salmon 6 



Trends in abundance for the entire system 11 



Comparative abundance among lakes 14 



Abundance in each lake of the system 16 



Coville Lake 16 



Grosvenor Lake 19 



Iliuk Arm 20 



South Bay 20 



West End 20 



North Arm 21 



Northwest Basin 21 



Brooks Lake 21 



Abundance of associated species 21 



Pond smelt 21 



Threespine sticklebacks 24 



Ninespine sticklebacks 24 



Interlake migration of presmolt sockeye salmon 25 



Migration from Coville Lake to Grosvenor Lake 26 



1961 26 



1962 26 



1963 27 



1964 27 



Migration from Grosvenor Lake to Iliuk Arm 27 



Significance of the summer outmigrations from Coville Lake 28 



Diel timing of migrations 29 



Behavior of schools of age fish at outlet of Coville Lake 31 



Early rearing areas of sockeye salmon fry from Grosvenor River and Hardscrabble Creek 31 



Size, length frequency, and growth 32 



Juvenile sockeye salmon 33 



Coville Lake and Coville River 35 



Grosvenor Lake and Grosvenor River 36 



Iliuk Arm 36 



South Bay 36 



West End 39 



North Arm 41 



Northwest Basin 41 



Brooks Lake 41 



Causes of differences in size of juvenile sockeye salmon on 1 September 41 



Real differences in rates of growth 41 



Differences in time of recruitment of fry 43 



Differences in rates of dispersion of large and small or fast- and slow-growing fish 43 



Differences in size of fry at time of emergence 44 



Species commonly associated with juvenile sockeye salmon 44 



Threespine sticklebacks 44 



Ninespine sticklebacks 44 



Pond smelt 44 



Pygmy whitefish and least cisco 46 



Predation on juvenile sockeye salmon 46 



Lake trout 46 



H umpback whitefish 48 



iii 



