Breeding site selection by coho salmon (Oncorhynchus kisutch) in relation to large wood additions and factors that influence reproductive success

Abstract

The fitness of female Pacific salmon (Oncorhynchus spp.) with respect to breeding behavior can be partitioned into at least four fitness components: survival to reproduction, competition for breeding sites, success of egg incubation, and suitability of the local environment near breeding sites for early rearing of juveniles. We evaluated the relative influences of habitat features linked to these fitness components with respect to selection of breeding sites by coho salmon (Oncorhynchus kisutch). We also evaluated associations between breeding site selection and additions of large wood, as the latter were introduced into the study system as a means of restoring habitat conditions to benefit coho salmon. We used a model selection approach to organize specific habitat features into groupings reflecting fitness components and influences of large wood. Results of this work suggest that female coho salmon likely select breeding sites based on a wide range of habitat features linked to all four hypothesized fitness components. More specifically, model parameter estimates indicated that breeding site selection was most strongly influenced by proximity to pool-tail crests and deeper water (mean and maximum depths). Linkages between large wood and breeding site selection were less clear. Overall, our findings suggest that breeding site selection by coho salmon is influenced by a suite of fitness components in addition to the egg incubation environment, which has been the emphasis of much work in the past.

Patterns of River Discharge and Temperature Differentially Influence Migration and Spawn Timing for Coho Salmon in the Umpqua River Basin, Oregon

“…Delays in spawning have been documented in many salmon species due to warm water temperatures (Webb and McLay 1996;Richter and Kolmes 2005;Quinn 2018). These results are also consistent with prior anecdotal observations (Neave 1943;Sandercock 1991;Clark 2013), which reported that initial annual peak discharge events tend to occur before the initiation of redd building for Coho Salmon.…”

Spatial Variability of Chinook Salmon Spawning Distribution and Habitat Preferences

“…We observed an increased frequency of multiple channels and pools with wood cover near the confluences of large tributaries, and in some cases (e.g., downstream reaches), we attributed the increased sediment and wood supply to the creation of patches of spawning habitat. Proximity of spawning habitat to complex cover is important for spawning site selection, but previous studies have focused on the proximity of redds to cover rather than the potential importance of cover as a driver of redd density (Senter and Pasternack 2011;Clark et al 2014). This is consistent with our observation of greater spawning within complex reaches, where adult holding pools and cover occurred in close proximity, but our modeling approach directly linked cover to increased redd densities in 3-km reaches.…”

“…Recent research suggests that spawning sites are associated with complex habitat types that support offspring after emergence (Falke et al 2013). For example, Clark at al. (2014) found that the proximity to complex juvenile rearing habitat, which likely increases reproductive success by conferring a survival advantage to juveniles, was important for spawning site selection.…”

“…The spawning habitat requirements of Pacific salmon at broad scales (i.e., watershed or segment scales) have been linked to habitat size and connectivity Isaak et al 2007), substrate quality, channel morphology (Coulombe-Pontbriand and LaPointe 2004), bedform morphology, hyporheic flow, and temperature (Hanrahan 2007a(Hanrahan , 2007b. Intermediatescale (i.e., reach or channel-unit scale) spawning habitat associations include sinuosity (Fukushima 2001), hydraulic gradient (Baxter and Hauer 2000), and pool tails (Clark et al 2014). Redd-scale spawning habitat characteristics have primarily been associated with depth, velocity, substrate size (Kondolf and Wolman 1993;McHugh and Budy 2004;Kondolf et al 2008), and hyporheic exchange (Geist et al 2002).…”

Large Wood and Instream Habitat for Juvenile Coho Salmon and Larval Lampreys in a Pacific Northwest Stream

“…Wood was arranged into 37 log jams. Large wood, as considered herein, consisted of pieces ≥ 15 cm in diameter and 3 m in length (Clark et al 2014;Jones et al 2014).…”