Return to the River will describe a new ecosystem-based approach to the restoration of salmon and steelhead populations in the Columbia River, once one of the most productive river basins for anadromous salmonids on the west coast of North America. The approach of this work has broad applicability to all recovery efforts throughout the northern hemisphere and general applicability to fisheries and aquatic restoration efforts throughout the world. The Pacific Northwest is now embroiled in a major public policy debate over the management and restoration of Pacific salmon. The outcome of the debate has the potential to affect major segments of the region's economy - river transportation, hydroelectric production, irrigated agriculture, urban growth, commercial and sport fisheries, etc. This debate, centered as it is on the salmon in all the rivers, has created a huge demand for information. The book will be a powerful addition to that debate. - A 15 year collaboration by a diverse group of scientists working on the management and recovery of salmon, steelhead trout, and wildlife populations in the Pacific Northwest - Includes over 200 figures, with four-color throughout the book - Discusses complex issues such as habitat degradation, juvenile survival through the hydrosystem, the role of artificial production, and harvest reform

The Behavior and Ecology of Pacific Salmon and Trout explains the patterns of mate choice, the competition for nest sites, and the fate of the salmon after their death. It describes the lives of offspring during the months they spend incubating in gravel, growing in fresh water, and migrating out to sea to mature. This thorough, up-to-date survey should be on the shelf of everyone with a professional or personal interest in Pacific salmon and trout. Written in a technically accurate but engaging style, it will appeal to a wide range of readers, including students, anglers, biologists, conservationists, legislators, and armchair naturalists.

A complex mosaic of estuarine habitats is postulated to bolster the growth and survival of juvenile Chinook salmon by diversifying the availability and configuration of prey and refugia. Consequently, efforts are underway along the North American Pacific Coast to return modified coastal ecosystems to historical or near-historical conditions, but restoring habitats are often more sensitive to anthropogenic or climate-mediated disturbance than relict (unaltered) habitats. Estuaries are expected to experience longer inundation durations as sea-levels rise, leading to reductions in intertidal emergent marshes, mudflats, and eelgrass beds. Furthermore, rising ocean temperatures may have metabolic consequences for fall-run populations of Chinook salmon, which tend to out-migrate during the spring and summer. Extensive monitoring programs have allowed managers to assess the initial benefits of management efforts (including restoration) for juvenile salmon at local and regional scales, but at present they have limited options for predicting and responding to the concurrent effects of climate change in restoring and relict coastal ecosystems. For my dissertation I addressed this gap in knowledge using a comprehensive monitoring dataset from the restoring Nisqually River Delta in southern Puget Sound, Washington. I focused on the following questions: 1) How do juvenile Chinook salmon prey consumption and dietary energy density vary throughout a mosaic of estuarine habitats, and is this variation related to differences in physiological condition? 2) How do among-habitat differences in thermal regime and prey consumption affect the bioenergetic growth potential of juvenile Chinook salmon? 3) How will shifts in the estuarine habitat mosaic vary under different sea-level rise and management scenarios? and 4) How will these climate- and management-mediated shifts in the estuarine habitat mosaic impact habitat quality for juvenile Chinook salmon? To address the first question, I used stomach content and stable isotope analyses to analyze the diets of wild and hatchery Chinook salmon captured in different estuarine habitats during the out-migration season (March-July of 2014 and 2015). I also linked measures of stomach fullness and dietary energy density to body condition. To address the second question, I used a bioenergetics model to determine how among-habitat differences in water temperature and diet might affect juvenile Chinook salmon growth. To address the third question, I designed and calibrated a marsh accretion model and decision support tool using post-restoration monitoring data sets and spatial coverages. Finally, to address the fourth question, I combined output from the marsh accretion model, a hydrological model, and measurements of prey availability into a spatially explicit version of the bioenergetics model to assess the habitat quality and growth rate potential of the entire estuarine habitat mosaic under different sea-level rise and management scenarios. When considered in tandem, these chapters represent a novel approach to habitat management. Assessments of juvenile salmon diet and physiology, marsh accretion models, and bioenergetics models have been independently implemented along the Pacific Coast, but the amalgamation of all three approaches into a single, spatially explicit analysis represents a novel and significant contribution to the scientific literature. In conducting these analyses for the Nisqually River Delta, some major themes emerged regarding the importance and vulnerability of specific habitats. An integrative diet analysis using stomach contents and stable isotopes found distinct dietary niches between wild and hatchery Chinook salmon. Wild fish were more likely to utilize the freshwater tidal forested and transitional brackish marsh habitats along the main stem river, where energy-rich insect drift made up most of their dietary biomass. The availability and consumption of insect prey resulted in distinct benefits to body condition and growth, as determined by direct physiological measurements and output from the habitat-specific bioenergetics model. These findings highlight the importance of freshwater and brackish emergent marsh habitats with overhanging vegetation, which can regulate water temperatures and supply insect drift. Unfortunately, freshwater tidal forests, brackish marshes, and low and high elevation emergent salt marshes are highly vulnerable to sea-level rise, especially when geological and anthropogenic features limit sediment accretion or lateral expansion. When spatial layers from the marsh accretion model were incorporated into the spatially explicit version of the bioenergetics model, output indicated that loss of low and high salt marsh reduced the amount of prey available for juvenile salmon, thus decreasing modeled growth rate potential. In all, these findings highlight the importance of preserving the estuarine habitat mosaic for out-migrating juvenile salmon, especially as tidal regimes and ocean temperatures continue to shift through time.

Estuaries provide juvenile salmonids with highly productive feeding grounds, refugia from tidal fluctuations and predators, and acclimation areas for smoltification. However, these dynamic, fluctuating salinity environments may also be physiologically stressful to growing juvenile fish. In order to evaluate the costs and benefits of estuarine marshes to juvenile Chinook salmon, I observed habitat use, diet, and growth of fish in the Nehalem Estuary on the Oregon coast. I also examined physiological costs associated with salmon living in fluctuating salinities and growth rates in laboratory experiments. I collected growth, diet and osmoregulation information from juvenile Chinook salmon in three tidal marsh sites in the Nehalem Bay and from juveniles in the Nehalem River. Stomach contents indicated that a high proportion of the diet is derived from terrestrial prey. These allochthonous prey resources likely become available during the flood stages of tidal cycles when drift, emergent and terrestrial insects would become available from the grasses surrounding the water. This field study confirmed that juvenile Chinook salmon utilized fluctuating salinity habitats to feed on a wide range of items including terrestrial-derived resources. Although field studies indicate that fish in estuarine habitats grow well and have access to quality prey resources, experimental manipulations of salinities were used to quantify the physiological costs of residing in the freshwater-saltwater transitional zone. In the laboratory, I designed an experiment to investigate the physiological responses to fluctuating salinities. Experimental treatments consisted of freshwater (FW), saltwater (SW) (22-25%o); and a fluctuating salinity (SW/FW) (2 - 25%o). These treatments were based on typical salinity fluctuations found in estuarine habitats. I measured length, weight, plasma electrolytes and cortisol concentrations for indications of growth and osmoregulatory function. The fluctuating salinity treatment had a negative effect on growth rate and initial osmoregulatory ability when compared with constant freshwater and saltwater treatments. The results indicated that fluctuating salinities had a small but marginally significant reduction in growth rate, possibly due to the additional energetic requirements of switching between hyper- and hypo-osmoregulation. However, 24-hour saltwater challenge results indicated that all fish were capable of osmoregulating in full-strength seawater. In a second experiment, I manipulated feed consumption rates of juvenile spring Chinook salmon to investigate the effects of variable growth rates on osmoregulatory ability and to test the validity of RNA:DNA ratios as indication of recent growth. The treatments consisted of three different feeding rates: three tanks of fish fed 0.7 5% (LOW) body weight; three tanks fed 3% (HIGH) body weight; and three tanks were fasted (NONE) during the experiment. These laboratory results showed a significant difference in the osmoregulatory ability of the NONE treatment compared to the LOW and HIGH treatments which indicates that a reduction in caloric intake significantly effected osmoregulatory capabilities during a 24 hour saltwater challenge. Furthermore, this suggests that there is a minimum energetic requirement in order to maintain proper ion- and osmoregulation in marine conditions. Estuarine marshes have the potential to provide productive feeding grounds with sufficient prey input from terrestrial systems. However, utilization of these marshes in sub-optimal conditions could alter behavior or impair physiological condition of juvenile Chinook salmon prior to their seaward migration by providing insufficient prey resources in a potentially stressful, fluctuating environment. Therefore, the physiological costs associated with estuarine habitat use should be well understood in order to aid future restoration planning.