Age and Growth of Trout in Sagehen Creek, California

MASTERS THESIS: Age and growth studies of eastern brook, rainbow, and brown trout were conducted from samples collected in 1951 through 1954 in Sagehen Creek, a tributary of the Truckee River, in east-central California. There was a general increase in size in all species of trout in the downstream direction. The average lengths of untagged trout in four study sections were compared. The eastern brook and rainbow trout grew at about the same rate; both, however, grew more slowly than the brown trout for the same section. The maximum growth for eastern brook trout occurred in the lower section with the average length decreasing both upstream and downstream from this area. Rainbow and brown trout both showed maximum growth in the lowest section from which samples were studied, with generally increasing size upstream. The differences in average size of the trout are best explained through influence of different water temperature upon physiological activity and on food consumption. In Sagehen Creek there is an increase of 13.8 degrees F in mean water temperatures from the upper to the lower sections. Each species of trout has an optimum temperature for growth which is reflected in the growth patterns between the different areas of the stream. The growth patterns of the eastern brook and brown trout demonstrate that the temperatures for maximum growth for eastern brook are lower than for brown trout. Population density affects growth through competition for food. There was no apparent correlation between the population density of all fishes of Sagehen Creek combined, and the growth rate of the trout Jaw-tagged eastern brook and rainbow trout grew more slowly than untagged fish of the same age, demonstrating that tagging in some manner is deleterious to growth. However, tagging had no apparent affect on the growth of brown trout. Examination of scales from 1953 sample demonstrated that rapid summer growth commenced about mid-June... Younger fish began growing sooner than older fish. There was no apparent difference in the time of commencement of summer growth in the various sections of the stream. Correlation of season growth patterns with the mean maximum and minimum water temperatures indicates that the summer growth period extends from mid-June to about October in Sagehen creek. Differences in average temperatures may extend or shorten the summer growth period by a few weeks in a given year. Both the eastern brook and rainbow trout of Sagehen Creek formed scales in their first summer of life; rainbow trout first forming scales at about 40mm in total lengt