Survival, Population Density, Growth, and Movement of the Wild Brown Trout in Crystal Creek

Abstract

A portion of the data accumulated in a 4-year study of the trout of Crystal Creek, New York State, is reported. An annual population inventory of the same 13 sample sections of the stream each September for 4 years provided information on survival, density of fish, growth, movement, and other factors. The percentage survival of the young brown trout of the year (age-group 0) in later years was found to be as follows: Second year (age-group I), 24.1; third year (age-group II), 11.0; fourth year (age-group III), 5.49; fifth year (age-group IV), 1.25; sixth year (age-group V), 0.48. The trout were subject to angling, which accounted for about 15 per cent of the yearly losses of the legal-sized fish. A considerable mortality of the larger-sized trout, for which the cause could not be determined, was observed each year during July. Hatchery fingerlings planted in September survived to the following September at rates varying from 0.25 per cent to 6.3 per cent (the latter figure is the more reliable). The survival of wild fingerling brown trout for this same period was 24.1 per cent, but might be expected to be higher than that of the hatchery fish as the latter were stocked in riff and in the relatively unproductive flat water alike. The numbers of wild legal-sized brown trout influenced the catch by anglers, for with 526 present in the 4.17 miles of stream in 1939, 0.275 fish were taken per hour as compared to catches of 0.192 fish per hour in 1940 when 424 were present, and 0.088 fish per hour in 1941 when 245 were present. Of the number of 2-year-old brown trout (age-group II) present, 26.5 per cent were caught by anglers, as compared to 22.6 per cent of the number of 3-year-olds, 12.0 per cent of the 4-year-olds, and only 8.83 per cent of the 5-year-olds. Throughout the stream there were an estimated 1,053 wild brown trout per mile of fast water as compared with only 481 per mile of slow water. Trout under 8.4 inches (total length) were more numerous in the fast water, and those 8.4 inches long or longer were more numerous in the slow water. On a per-mile basis there were on the average 421 fingerlings, 106 yearlings, 48.6 2-year-olds, 31.1 3-year-olds, 11.2 4-year-olds and 5.0 5-year-olds each year. The average length of wild fingerlings in the fast-water areas (3.24 inches) was significantly greater than the average of 2.92 inches for those in the slow-water areas. The lengths in inches in September for the various age groups were as follows: 0 group, 3.09; I group, 5.69; II group, 7.56; III group, 10.15; IV group, 11.65; V group, 14.02. The weights in grams for fish of these ages were 4.8, 27.0, 75.1, 182.9, 263.6, and 435.2, respectively. Movement of the wild brown trout from September to September was surprisingly slight; most fish were found where originally tagged. Most ascended the stream in October and November but returned to their original locations.