This project will provide information on the relative abundance of juvenile Chinook salmon, coho salmon, three-spine stickleback and the presence and absence of Dolly Varden char, rainbow trout and sculpin. This project will build upon ARRI’s previous juvenile salmon monitoring efforts by providing information on the significance of different streams for juvenile Chinook and coho salmon. The sampling can be used to assess the effects of human development on juvenile Chinook and coho salmon rearing and overwintering, and describe important summer rearing habitats. Sampling will be conducted for 2 years at approximately 16 stream locations in key tributaries and mainstem habitats.
Timeline: November 2015-November 2017
Objective 1 observations: Juvenile Chinook and Coho overlapped in their distribution, with both species present at most of the study sites. However, there is an indication of spatial segregation among study sites. At sites where both species were present, their relative abundances were inversely proportional, with generally low juvenile coho catch per unit trap (CPUT) at the sites with greater than average juvenile Chinook CPUT.Objective 2 observations: For Coho, the difference in relative abundance was not explained by differences in stream size or classification. For Chinook, there was no difference in relative abundance between upland and wetland streams. Relative abundance was highly variable within each stream class, but sites with relatively high CPUT (>3.0) were all large 3rd order streams, although not all large streams had high CPUT. In addition to the largest cross-section channel area, these streams had the lowest slopes, and were deeper than other stream types, however there were no other water quality or physical habitat characteristics that distinguished these streams from other classification types. There was some indication that juvenile salmon growth rates were faster in warmer streams, though other factors may explain this observation.Objective 3: Small-scale habitat characteristics were measured at each trap location in 2017 & 2017; however, habitat suitability criteria and indices are still being developed with combined 2016 & 2017 results. Habitat suitability indices will be used to evaluate differences in CPUT among sampling sites and stream classification types.