Juvenile Coho Salmon Growth and Survival across Stream Network Seasonal Habitats

Abstract

Understanding watershed-scale variation in juvenile salmonid survival and growth can provide insights into factors influencing demographics and can help target restoration and mitigation efforts for imperiled fish populations. We assessed growth, movement, and apparent overwinter survival of individually tagged juvenile coho salmon Oncorhynchus kisutch in a coastal Oregon watershed from June 2002 to June 2003 and related growth and survival parameters to stream characteristics. Fall body size of juvenile coho salmon was a good predictor of smolt size and survival, but smolt size was also influenced by overwintering location. This was due to strong spatial patterns in winter growth rates associated with residency and movement into a small intermittent tributary. Though nearly dry in midsummer, this stream supported high densities of spawning coho salmon in the fall, and juveniles rearing there exhibited relatively high growth rates and emigrated as larger smolts. Improved winter growth and survival of juvenile coho salmon utilizing tributary habitats underscore the importance of maintaining connectivity between seasonal habitats and providing a diversity of sheltering and foraging opportunities, particularly where main-stem habitats have been simplified by human land uses.

Changes in fish communities following recolonization of the Cedar River, WA, USA by Pacific salmon after 103 years of local extirpation

“…Also, if exotic species are below or above the barrier, management measures should be implemented to limit their dispersal and interactions with targeted species. Our study also showed that access to small streams was particularly important for juvenile rearing, and tributaries of larger rivers can provide important growth and survival benefits to juvenile salmon (Ebersole et al 2006). …”

Geomorphic and Ecological Consequences of Riprap Placement in River Systems

“…Many individual species require a narrow range of substrate textures in order to thrive. Species that bury eggs in gravel substrate, such as salmonids, require material that is not too coarse to mobilize, but not so fine as to restrict water and oxygen circulation, and that remains mostly submerged through the incubation period (Beschta and Platts, 1986;Ebersole et al, 2006). In summary, transported sediment and in-channel features (such as log jams and complex banks) provide a varied and refreshed substrate that can accommodate the requirements of many species.…”

Winter stream temperature in the rain-on-snow zone of the Pacific Northwest: influences of hillslope runoff and transient snow cover

“…In contrast to the depth and breadth of research on summer stream temperature, few studies have examined winter stream temperature processes despite its recognized importance for aquatic ecosystems (Beschta et al, 1987;Holtby, 1988;Ebersole et al, 2006;Brown et al, 2011;Shuter et al, 2012). Salmonids are poikilothermic, so decreases in stream temperature correspond with declines in metabolic processes and the ability of fish to swim, feed, and avoid predators (Brown et al, 2011).…”