Chinook salmon (Oncorhynchus tshawytscha) density, growth, mortality, and movement in two Lake Michigan tributaries

Abstract

Spawning density and the time of spawning (October) were similar in two tributaries of Lake Michigan in 1977 and 1978. Drift of recently emerged fry began in April and continued into June. During 1977–1979, the density of chinook salmon juveniles increased rapidly in early May to 0.3–2.9 fish/m2 and then declined to 0.2–0.8 fish/m2 by late June when most of the fish smolted. Instantaneous mortality estimates were variable between years and sites in both creeks, but overall mortality was similar in both streams with an average daily rate of 0.024 for Baldwin Creek and 0.025 for Pine Creek. A regression of the mortality rates versus initial density indicated the mortality rates were dependent on the initial fry density. There was no correlation between an index of spawner density and the number of smolts produced. No correlation was found between initial resident fry density and emergent fry colonization. Size-selective mortality was indicated in some stream sections. The daily growth rates for fish in both streams varied between 0.28 and 1.01 mm per day. These rates were similar to or higher than rates reported in the literature from other stocks of chinook salmon on the west coast of North America and Lake Ontario.