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If you have any questions on the information presented, or require additional report data or attachments, please contact the Report Contact
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This report contains information on adult summer and winter steelhead in the Nass River Watershed, gathered from a variety of sources covering the years from 1974 to 1996.
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Author: Cascadia Natural Resource Consulting
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Old Reference Number: sk110
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Date Published: Jul 1997
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Report ID: 2605
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Audience: Government and Public
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Information on populations of adult summer (Cranberry River, Damdochax Creek, Kwinageese River, Meziadin River, Nass River fishwheels) and winter (Chambers Creek, Ishkheenickh River, Tseax River) steelhead in the Nass River
watershed was gathered from a variety published technical reports and unpublished data from the Skeena Region Ministry of Environment, Lands and
Parks files (Smithers). The information was pooled among years (1974 to 1996) and sampling methods to increase sample sizes and improve inferences on the life history characteristics specific to the Nass habitat capability model. Male and female steelhead were generally similar in
body size within tributary populations. Among summer steelhead, Damdochax steelhead were similar in body size to Kwinageese and Meziadin steelhead, however Damdochax steelhead were larger than Cranberry steelhead. Winter
steelhead populations were similar in body size, and they were generally larger than summer steelhead populations. Mean smolt age ranged from 3.00 years (Meziadin River) to 3.74 years (Damdochax Creek) and steelhead were most frequently freshwater age 3 or 4 in the Nass River watershed. Fecundity estimates ranged from 2597 eggs per fish (Cranberry River) to 4264 eggs per fish (Chambers Creek) and were generally higher for winter than summer steelhead, due to the larger body size of winter steelhead. Life history characteristics and provincial biostandards were used to estimate the relative productivity of Nass River steelhead populations. Winter steelhead populations were generally more productive than summer steelhead populations due to larger body size. For winter steelhead, Chambers Creek was
the most productive and Tseax River was the least productive. Among summer steelhead, the Meziadin River population was the most productive and the Cranberry River population was the least productive. Life history model estimates (i.e. recruits per spawner, allowable harvest rates, Beverton-Holts A value) were lower when calculated with updated biostandards than with biostandards used in the Skeena steelhead
carrying capacity model. Monte Carlo simulations indicated the high variability in the updated
biostandards increased the probability of populations not meeting sufficient recruitment levels for replacement due to natural (random) variability. The most sensitive life history model parameter was mean smolt age, followed by egg to fry Nass River steelhead life history characteristics
survival, smolt to adult survival and female length, when older biostandards were used (from 1992). However, when the variability of the updated biostandards was incorporated, the most sensitive parameter was smolt to adult survival, followed by
egg to fry survival, mean smolt age and female length. Mean smolt age was probably underestimated for Nass River populations because of limitations in scale aging techniques and the short growing season that probably exists for a number of rearing streams in the Nass River watershed. These negative bias errors in
mean smolt age result in overestimates of recruits per spawner, allowable harvest rates and Beverton-Holts A value.
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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 - Management |
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Watershed Groups - 500 - Nass River |
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