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Report: Estimating the Abundance of Adult Steelhead in the Babine River Using Mark Recapture Methods 1992 - 1993.
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This report summarizes a stocking assessment of adult steelhead in the Babine river during the 1992 - 1993 field season. The report is 20 pages long. For an abstract, see the long description.
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Author: Bison, R.G.
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Date Published: Jan 1993
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Report ID: 1701
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Audience: Government and Public
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A mark recapture study was conducted by angling on the upper 20 kilometers of the Babine River in an attempt to estimate the abundance of overwintering adult steelhead. The initial tagging was conducted by fisheries staff and volunteers during the 1992 fishing season. A total of 473 steelhead was considered to be the first sample of this mark recapture study. This total was used to develop a sampling strategy that would produce acceptable statistical precision. The sampling strategy was also designed to ensure as much accuracy as possible by minimizing the potential violation of mark recapture assumptions. Multiple census methods were expected to be better estimators than single census methods and therefore two subsequent recovery phases were conducted. Each of these two subsequent samples required eight angler days to complete and both were conducted in early April. Three Petersen estimates with 95 percent confidence limits were 4077 (3266-5396), 3623 (2688-5234), and 4660 (3072-7915). Three multiple census estimates were consistently lower than the Petersen estimates. These were the Schumacher at 3407 (2636-4817), the Original Schnabel at 3450 (2261-7273), and the Modified Schnabel at 3399 (2717-4381). Multiple census results suggested there may have been some violation of mark recapture assumptions. A corrective method applied to the data (Tanaka Model) produced an estimate of 2083 steelhead in the study area. Confidence limits could not be derived using this method because the number of sampling periods was too few. Nevertheless, the Tanaka estimate was considered to reflect the degree of possible inaccuracy in the other estimates. A number of possible violations of mark recapture assumptions were identified. However, from a stock monitoring perspective, the most serious problem in estimating the overwintering population of the Babine River was the uncertainty about annual variability in the distribution of the population. For this reason, an annual census of the overwintering population in the Upper Babine alone may be of limited use for stock monitoring purposes. It is recommended that an attempt be made to operate the Babine River fence during the spring. If a large and constant proportion of the total river spawning population does, as assumed, utilize the spawning area immediately upstream, fence operation should provide a useful index of abundance.
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Report Type
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Fish and Aquatic Habitat Information |
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Subject
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Fish Species - Steelhead - Oncorhynchus mykiss |
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Region - Skeena |
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Fish and Fish Habitat - Stock Assessment |
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Watershed Groups - 480 - Babine River |
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