Staff of the U. S. Fish and Wildlife Service and U. S. Geological Survey has responded to emerging issues relative to the recovery of Snake River fall Chinook salmon through project 199102900 for 15 years.   We propose to help managers increase fall Chinook salmon production in the free-flowing Snake River by using existing and newly collected field data to answer five critical questions: (1) is the progression of life history events changing over time; (2) is growth during rearing and seaward movement changing over time; (3) could survival to the tailrace of Lower Granite Dam be increased; (4) could interactions between wild and hatchery smolts be reduced; and (5) does summer spill benefit fall Chinook salmon migrants?  We answer these questions by accomplishing the following five objectives: (1) increasing the effectiveness of hydrosystem operations; (2) maximizing growth of wild fall Chinook salmon; (3) increasing the survival of wild fall Chinook salmon subyearlings; (4) reducing the potential for wild-hatchery fish interaction; and, (5) increasing the understanding of the efficacy of spill.  To accomplish our objectives, we will PIT tag wild subyearlings and analyze subsequent detection data to estimate survival, growth, describe run timing and life history attributes, and evaluate the effectiveness of summer spill.  We will explore the roles of food availability, growth, and habitat rearing capacity as potential limiting factors to Snake River fall Chinook salmon.

COORDINATION

This is a collaborative project conducted by staff of the U.S. Fish and Wildlife Service (USFWS), U.S. Geological Survey (USGS), and the University of Idaho (UOI).  Each of these groups brings expertise in fish tagging and data analyses specific and complimentary to the project's five objectives.  Staff of the USFWS is primarily responsible for accomplishing objective 3-5  activities that focus on tagging fish with passive integrated transponders (PIT tags), uploading the tagging data to a central database, and providing managers with in-season and post-season analyses.  Staff of the USGS is primarily responsible for accomplishing objective 2 activities that focus on analyses of new and existing PIT-tag data, new data on feeding habits, and existing data on rearing habitat availability.  Staff of the UOI are primarily responsible accomplishing objective 1 activities that focus on compiling and analyzing historical and new data .  Staff of all three groups coauthor refereed articles in international journals.  This project is cost-shared by the U. S. Army Corps of Engineers (USACE), Idaho Power Company (IPC), and the USFWS.  

GOAL

Our research goal is to provide fishery managers with in-season and post-season data for addressing emerging issues relative to systemwide hydrosystem operation.  

OBJECTIVES AND RATIONALE

Objective 1:  Increase the effectiveness of hydrosystem operations intended improve wild fall Chinook salmon survival by determining if the progression of wild fall Chinook salmon life history events is changing over time due to biological or physical alterations in the environment.

We hypothesize that wild fall Chinook salmon will disperse from natal riverine habitat and pass the lower Snake River dams earlier as adult escapement and densities in the rearing areas increases.  If this hypothesis is true, the implication for adaptive hydrosystem management would be that timing summer flow augmentation and summer spill should be dependent on variability in life history progression opposed to a fixed schedule based on historical data (e.g., June 20 to 31 August).  To accomplish objective 1 and test this hypothesis, staff of the USFWS and UOI will beach seine and PIT tag wild subyearling fall Chinook salmon along the Snake River.  Staff of UOI will use beach seining and PIT-tag data collected during 1992-2009 to determine if: (1) emergence timing varies by year and is directly proportional to winter-spring temperatures and (2) the timing of parr presence and smolt passage at dams vary by year and are indirectly proportional to redd counts, CPUE, the number of hatchery subyearlings released, maximum flow, and flow pulse rate.  The main finding of Objective 1 might be that wild fall Chinook salmon disperse from natal riverine habitat and pass the lower Snake River dams earlier than observed during the 1990s because adult escapement and densities in the rearing areas increased resulting in density-dependent downstream movement.


Objective 2: Maximize growth of wild fall Chinook salmon by determining how growth and condition of wild fall Chinook salmon during rearing and seaward movement are affected by changing biological and environmental conditions.

We hypothesize that wild fall Chinook salmon growth in fork length (mm/d), condition factor, and robustness (i.e., in body shape) will decrease and then stabilize across years as juvenile densities in the rearing areas and Lower Granite Reservoir increase and approach carrying capacity.  In the case of the reservoir, however, growth and robustness in fish sampled within a year from May to October will increase as rearing densities decrease after peak migration leaving only those fish destined to become reservoir-type juveniles.  To accomplish objective 2 and test this hypothesis; staff of the USGS will analyze growth records and body morphology established for PIT-tagged fish during 1995-2009, collect stomach contents of fish for food habitat analyses, and estimate rearing densities based on existing habitat data for the Snake River and the Hanford Reach of the Columbia River.  Analyses will determine if: 1)  if the density of wild fall Chinook salmon in riverine habitat has increased over time and then stabilized as carrying capacity was achieved at densities similar to those estimated for the Hanford Reach; 2) growth of parr and smolts was directly proportional to temperature, but dependent on an interaction between temperature and density dependent factors that caused growth to decrease at a given temperature as density increased; 3) the millions of hatchery subyearlings released for supplementation in May dispersed downstream rapidly into the reservoir and depleted the food supply available for wild fall Chinook salmon subyearlings and in contrast to earlier findings smolt growth in the warmer waters of Lower Granite Reservoir did not exceed those observed in the relatively cooler water of the riverine habitat; 4) the fish collected during the 1990s were more robust than those in the present-day samples and robustness increased from May to October within a year because rearing densities decreased after July and food was plentiful for the fish destined to become reservoir-type juveniles.  The main adaptive management implication of Objective 2 results might be that a balance exists between the benefits and detriments of supplementation; supplementation likely increases adult escapement and production, but results in a density dependent decrease in juvenile growth, condition, and body robustness.

Objective 3: Increase the survival of wild fall Chinook salmon subyearlings by determining if the joint probability of active migration and survival to the tailrace of Lower Granite Dam is affected by biological or physical alterations in the free-flowing river environment during the latter period of rearing.

We hypothesize that the joint probability of wild fall Chinook salmon actively migrating and surviving to the tailrace of Lower Granite Dam is influenced to a larger extent by reservoir conditions during the early period of seaward movement than by riverine conditions during the latter period of rearing; however, additional increases in this joint probability could be realized by elevating or pulsing discharge from the Hells Canyon Complex during the latter portion of shoreline rearing.  To accomplish objective 3 and test this hypothesis, staff of the USFWS will use the PIT-tag data (1998-2009) collected for objective 1 together with flow and temperature data to determine if: the regression model with the best fit for predicting the joint probability of active migration and survival to the tailrace of Lower Granite Dam includes the predictor variables mean temperature during the early period of seaward movement in Lower Granite Reservoir (negative regression coefficient), the interaction term mean fork length during the latter period of rearing in riverine habitat x mean temperature during the early period of seaward movement (positive coefficient), and the interaction term mean flow during the latter period of rearing in riverine habitat x mean temperature during the early period of seaward movement (positive coefficient).  The interaction terms would function to increase the predicted joint probability of wild fall Chinook salmon actively migrating and surviving to pass Lower Granite Dam when temperature is held constant, but fork length and flow are increased.  These results would support the adaptive management alternative of increasing flow from the Hells Canyon Complex during the latter period of rearing in riverine habitat in May and June.

Objective 4: Reduce the potential for wild-hatchery fish interaction by determining if acclimating hatchery fall Chinook salmon subyearlings leads to different behavioral and life history patterns when contrasted to hatchery subyearlings that are released directly and wild fall Chinook salmon subyearlings.

We hypothesize that Lyons Ferry Hatchery fall Chinook salmon subyearlings that are acclimated prior to release into the free-flowing Snake River upstream of Lower Granite Reservoir will pass the lower Snake River dams earlier, take fewer days after release to pass these dams, have a higher probability of actively migrating and surviving to pass these dams, exhibit faster growth and higher condition, and be more likely to express an ocean-type juvenile life history than Lyons Ferry Hatchery fall Chinook salmon subyearlings that are directly released and wild fall Chinook salmon subyearlings.  To accomplish objective 4 and test this hypothesis, staff of the USFWS will use existing and new PIT-tag data (2005-2009; cost-shared by USACE and USFWS) to determine if: 1) Lyons Ferry Hatchery fall Chinook salmon subyearlings that were acclimated prior to release into the free-flowing Snake River upstream of Lower Granite Reservoir passed the lower Snake River dams earlier, 2) took fewer days after release to pass these dams, 3) had a higher probability of actively migrating and surviving to pass these dams, 4) exhibited faster growth and higher condition, and 5) were more likely to express an ocean-type juvenile life history than Lyons Ferry Hatchery fall Chinook salmon subyearlings that were directly released and wild fall Chinook salmon subyearlings.  The adaptive management implications of these findings might be that acclimation is a beneficial process because it reduces the potential for interaction between hatchery and wild subyearlings.

Objective 5:  Increase the understanding of the efficacy of spill by determining if summer spill decreases travel time and increases the joint probability of fall Chinook salmon actively migrating and surviving from Lower Granite Dam to the tailrace of McNary Dam.

We hypothesize that summer spill will reduce forebay delay at each of the Lower Snake River dams; thereby decreasing the time it takes fall Chinook salmon subyearlings to pass from Lower Granite Dam to McNary Dam, reducing the duration of exposure to warm summer temperatures and predators, and increasing the joint probability of active seaward migration and survival from Lower Granite Dam to the tailrace of McNary Dam.  To accomplish objective 5 and test this hypothesis, staff of the USFWS will use PIT-tag data (2005-2009; cost shared by USACE) to determine if: 1) summer spill reduced forebay delay at each of the Lower Snake River dams; thereby, decreasing the time it took fall Chinook salmon subyearlings to pass from Lower Granite Dam to McNary Dam and reducing the duration of exposure to warm summer temperatures and predators, and 2) increased the joint probability of active seaward migration and survival from Lower Granite Dam to the tailrace of McNary Dam.  The adaptive management implication of these joint findings might be that some level of summer spill should be implemented annually.