Emigration and stream residency of juvenile steelhead in Hurdygurdy Creek, California

I examined the emigration, growth, and stream residency of steelhead (Oncorhvnchus mykiss) in Hurdygurdy Creek, California, a tributary to the South Fork Smith River, in Del Norte County. Outmigration was monitored by weekly operation of a fyke trap from 2 April to 11 November 1988. Steelhead captured as outmigrants were measured in length to the nearest mm and weighed by displacement of water. Stream residency was monitored each month from April though November by direct snorkel observation samples of 14 habitat units. Water temperature was measured during the evening once per week throughout the study period. Discharge was calculated from South Fork Smith River stream gauge data. Age class by length was determined from a length-frequency histogram and scale analysis. A total of 11,525 steelhead were captured during the study period, 88 percent of which were captured between 17 April and 13 July. Age 0 steelhead accounted for 99.6 percent of the total number of emigrant steelhead. A total of 46 age 1 steelhead were trapped, five of which were smolts. The number of steelhead emigrating was positively correlated with stream discharge. The density of steelhead residing in the stream peaked in July and declined through August and September. The decline of steelhead residing in the stream did not coincide with an apparent increase in emigration. A comparison of age class proportions between emigrants and residents showed significantly more age 1 steelhead residing in the stream during July and August than emigrating. It is possible that a significant proportion of steelhead spawned in Hurdygurdy Creek grow to smolts lower in the Smith River basin.