Comparative Dispersal Patterns for Recolonizing Cedar River Chinook Salmon above Landsburg Dam, Washington, and the Source Population below the Dam

Abstract

Anadromous salmonid populations are particularly vulnerable to migration blockages, such as dams and culverts, because access to historic spawning and rearing habitats is prevented. The process of salmonid recolonization has not been well documented for river systems where anthropogenic migration barriers have been removed or where fish passage facilities have been constructed. In September 2003, Seattle Public Utilities completed construction of a fish passage facility that circumvented Landsburg Dam on the Cedar River, Washington. Chinook Salmon Oncorhynchus tshawytscha spawned in newly available main‐stem habitats immediately after fish passage facility construction and in all subsequent years. Further dispersal into tributary habitats occurred 5 years after construction. Redds tended to be concentrated in the downstream third of the available habitat above the dam, although some fish did utilize suitable spawning sites throughout the main stem, even in the uppermost reaches of the newly available habitat. Median spawn timing for redds observed above the dam was not significantly different from spawn timing for the source population, indicating that migration delays through the fish passage facility were minimal. Male Chinook Salmon consistently outnumbered females, with annual sex ratios ranging from 1.3:1 to 4.7:1. Chinook Salmon spawning above the dam contributed between 2.7% and 14.7% of the total annual redd count (2003–2010) for Cedar River Chinook Salmon; upstream redds as a percentage of total redds increased over time, indicating that a new, naturally reproducing population above the dam was growing. The proportion of hatchery‐origin fish spawning above the dam decreased over the duration of the study but was consistently higher than the hatchery component observed below the dam.

Dispersal and productivity of Chinook (Oncorhynchus tshawytscha) and coho (Oncorhynchus kisutch) salmon colonizing newly accessible habitat

“…Salmon of both species spawn in the Cedar River below the dam. Chinook salmon abundance below the dam was assessed by counts of spawning nests or "redds" in the Cedar River (Burton et al 2013). We obtained scale and, in some cases, fin tissue samples from adult Chinook salmon carcasses from the lower river surveys in 2006-2009.…”

“…Adult Chinook and coho salmon were counted and sampled as they ascended the fish ladder and bypassed the dam (Kiffney et al 2009;Anderson et al 2010Anderson et al , 2013aBurton et al 2013). Each sampled fish was identified by species and sex, and we took a small tissue sample for subsequent DNA analysis.…”

“…For these years, we estimated coho salmon abundance based on data from the camera system or the mean proportion from 2003 to 2009 that was trapped on or prior to the last date of sampling (if camera data were not available). We used spawning surveys by inflatable raft (Cedar River) and foot (tributaries) to quantify upstream dispersal distance from the dam by adult salmon (Burton et al 2013).…”

Linking resource availability and habitat structure to stream organisms: an experimental and observational assessment

“…We did not quantify the influence of adult salmon-derived nutrients on juvenile coho growth in the field because reach-scale, cumulative spawning density estimates were extremely low in the main stem and there was no spawning in Rock Creek (Table 1; Burton et al 2013). Moreover, in previous experiments and field observations in the Cedar River, this range of adult inputs had no detectable effect on nutrient chemistry, algal biomass, invertebrate population biomass, fish growth, and stable isotope ratios of d 13 C and d 15 N of invertebrates or fish (Cram et al 2011;P.…”

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“…Once a barrier is removed, the biological response to restored sediment transport and river connectivity can also be quite rapid O'Connor et al 2015). Chinook Salmon Oncorhynchus tshawytscha immediately colonized newly accessible habitat above Landsburg Dam on the Cedar River, Washington (Anderson et al 2014a;Burton et al 2013). Milner et al (2011) found that colonization of Pink Salmon O. gorbuscha and Dolly Varden O. malma occurred within 10 years in a stream formed after glacial recession and Coho Salmon O. kisutch were in abundance shortly thereafter.…”