Juvenile coho salmon movement, growth and survival in a coastal basin of southern Oregon

Abstract

Juvenile salmonids display highly variable spatial and temporal patterns of early dispersal that are influenced by density-dependent and density-independent factors.Although juvenile coho salmon (Oncorhynchus kisutch) movement patterns in streams and their relationship with body mass and growth have been examined in previous studies, most observations were limited to one season or one stream section. In this study, we monitored the movement of juvenile coho salmon throughout their period of residence in a coastal basin to identify prevalent dispersal strategies and their relationships with body mass, growth rates and survival. Our results revealed seasonally and spatially variable movement patterns. Juvenile coho salmon that dispersed to tidally affected reaches soon after emergence remained more mobile and expressed lower site fidelity than those individuals that remained in upper riverine reaches. We did not detect significantly different growth rates between sedentary and mobile individuals. Although a greater proportion of sedentary than mobile fish survived winter to emigrate from the creek in the spring, reach of residence at the onset of winter influenced these survival estimates. Hence, apparent summer-to-smolt survival for mobile individuals was greater than for sedentary fish in tidally influenced reaches, whereas in riverine reaches the sedentary strategy seemed to be favoured. Our research identified complex movement patterns that reflect phenotypic and life history variation, and underscores the importance of maintaining diverse freshwater and estuarine habitats that support juvenile coho salmon before marine migration. K E Y W O R D Scoho salmon, condition dependence, life history, movement, tide gate

Using Applied Science for Effective Watershed Restoration and Coho Salmon Recovery in Coastal Oregon Streams

“…Collectively, the LCM studies advanced the understanding of coho salmon, revealing at least two different life history strategies: (1) remain sedentary during the juvenile rearing period, and 2be mobile throughout the stream system, likely in response to food availability and stream temperatures, and apparently correlated with greater marine survival [13]. These multiple coho life histories are likely bolstering their resilience in highly dynamic and frequently perturbed systems, as has been found in other cases [15,16].…”

“…Streams were fenced to prevent livestock from trampling banks, and 63,700 willows and other (1) generated estimates of juvenile freshwater survival and adult marine survival over five brood years (see Figure 6), and provided reliable estimates of natural-origin coho jack returns [11][12][13];…”

“…(3) monitored juvenile and adult coho movement using PIT tags to show a correlation between higher coho mobility during winter months and lower winter survival, suggesting that a lack of accessible refugia puts fish at greater risk when seeking refuge from highvelocity flows [13];…”

Longitudinal Patterns of Juvenile Coho Salmon Distribution and Densities in Headwater Streams of the Little Susitna River, Alaska

“…Further, the contrasting thermal environment presented by headwater streams peripheral to areas of core production may contribute to a more complex thermal landscape, which provides opportunities for juveniles to engage in behavioral thermal regulation (Armstrong and Schindler ; Baldock et al. ) or exhibit life history diversity in terms of out‐migration timing (Johnson ; Weybright and Giannico ).…”

“…Although high-gradient systems with low groundwater influence may not provide a core habitat type, they may provide habitat features consistent with the needs of juvenile Coho Salmon at different life stages. Further, the contrasting thermal environment presented by headwater streams peripheral to areas of core production may contribute to a more complex thermal landscape, which provides opportunities for juveniles to engage in behavioral thermal regulation (Armstrong and Schindler 2013;Baldock et al 2016) or exhibit life history diversity in terms of out-migration timing (Johnson 2016;Weybright and Giannico 2018).…”