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Rebecca A. Buchanan

Publications and source records attributed to Rebecca A. Buchanan.

8 recordsLinked to original sources
USGS2025

Modeling climate and hydropower influences on the movement decisions of an anadromous species

In large river basins, migratory fish populations are threatened by the combination of hydropower and climate change. With river temperatures rising and hydropower development increasing globally, the longstanding monitoring programs for threatened Pacific salmon populations in the Columbia River Basin present an opportunity to study these impacts over extended time scales. We fit a statistical model to 20 years of PIT-tagging data to jointly model the effects of temperature and dam operations (spill management) on the movement of Steelhead (anadromous Oncorhynchus mykiss ) during their adult pre-spawn migration. We modeled the relationship between these factors and behaviors that pose mortality risks, including natal tributary overshoot (ascending a dam upstream of a natal tributary) and non-natal tributary use. We then used the posterior distributions of model-estimated parameters to predict the homing success of fish to natal tributaries under different climate and hydropower scenarios. Across the populations in our study, movement decisions were consistently thermally influenced, with temperature having a negative relationship with natal homing and a positive relationship with both natal tributary overshoot and non-natal tributary use. Another consistent finding across the populations in our study was that higher overshoot rates were associated with lower homing rates. Despite data limitations associated with the PIT-tag array network, we found evidence for population-specific benefits of winter spill on natal homing success, which is currently being implemented to assist the downstream migration of overshooting Steelhead. We demonstrate how integrating the effects of climate and hydropower management actions with movement ecology provides powerful insights into how species may respond to future scenarios. In our case study, we found that pre-spawn mortality of Steelhead is likely to increase with future climate change due to temperature-driven interactions with the hydrosystem, but there is potential for hydropower managers to partially offset these impacts.

Idaho, Montana, Oregon, Washington↗
USGS2025

Survival, travel time, and use of migration routes by juvenile steelhead in a modified river estuary

Greater understanding of the survival, travel time, and spatial distribution of juvenile salmonids among migration routes between their natal streams and the ocean is critical to the recovery of these threatened species. In the Sacramento–San Joaquin River Delta (Delta), a highly modified estuary in central California, USA, there is a critical need to evaluate how water management (e.g., water pumping) and environmental factors (e.g., water flow) impact these populations. While management actions can affect some environmental variables in the Delta, only recently have studies begun to uncover associations between these variables and key demographic parameters. In this study, we examine the effects of freshwater flows, water exports, tidal environment, and a temporary barrier on juvenile steelhead ( Oncorhynchus mykiss ) survival, travel times, and migration routing using a multiyear acoustic telemetry dataset and recent advancements in Bayesian multistate mark-recapture modeling. We found that no single covariate explained variation in juvenile steelhead population dynamics across the entire Delta, but that separate regions within the Delta showed association with specific environmental factors.

California↗
USGS2016

Anadromous salmonids in the Delta: New science 2006–2016

As juvenile salmon enter the Sacramento–SanJoaquin River Delta (“the Delta”) they disperse among its complex channel network where they are subject to channel-specific processes that affect their rate of migration, vulnerability to predation, feeding success, growth rates, and ultimately, survival. In the decades before 2006, tools available to quantify growth, dispersal, and survival of juvenile salmon in this complex channel network were limited.Fortunately, thanks to technological advances such as acoustic telemetry and chemical and structural otolith analysis, much has been learned over the past decade about the role of the Delta in the life cycle of juvenile salmon. Here, we review new science between 2006and 2016 that sheds light on how different life stages and runs of juvenile salmon grow, move, and survive in the complex channel network of the Delta. One of the most important advances during the past decade has been the widespread adoption of acoustic telemetry techniques. Use of telemetry has shed light on how survival varies among alternative migration routes and the proportion of fish that use each migration route. Chemical and structural analysis of otoliths has provided insights about when juveniles left their natal river and provided evidence of extended rearing in the brackish or saltwater regions of the Delta. New advancements in genetics now allow individuals captured by trawls to be assigned to specific runs. Detailed information about movement and survival in the Delta has spurred development of agent-based models of juvenile salmon that are coupled to hydrodynamic models. Although much has been learned, knowledge gaps remain about how very small juvenile salmon (fry and parr) use the Delta. Understanding how all life stages of juvenile salmon grow, rear, and survive in the Delta is critical for devising management strategies that support a diversity of life history strategies.

California↗
USGS2012

Snake River fall Chinook salmon life history investigations: Annual report 2010

This report summarizes three research activities conducted in 2010-2011. The first was a radiotelemetry study conducted in the lower Clearwater River. The second was a hydroacoustic study conducted in Lower Granite and Little Goose reservoirs. The third was an analysis of covariates affecting juvenile fall Chinook salmon survival and behavior. In 2010, we used radiotelemetry to evaluate the migratory behavior, delay, and relative mortality of subyearling fall Chinook salmon in the Clearwater River and Lower Granite Reservoir. We captured, tagged, and released a total of 100 run-at-large subyearlings in the Transition Zone of the lower Clearwater River in late July and monitored their downstream movement past fixed detection sites and by mobile tracking through the end of August. The Transition Zone is that portion of the river where it transitions from free-flowing to impounded habitat. Median residence time of fish that passed through the Transition Zone, Confluence, and Upper Reservoir reaches was relatively short (8.8-25.6 h). However, for fish that remained in the Transition Zone that were detected by mobile tracking, median residence time was over 30 d (N=6). Median migration rates through the study reaches were variable but slow (range 2.9-17.2 km/d) compared to that of more active migrants indicating that subyearlings from the Clearwater River were not actively migrating during July and August. The fate of radio-tagged subyearlings was determined from mobile tracking records. A total of 37 of the 71 fish detected during tracking were deemed to be dead, 22 were determined to be alive, and the fate of 16 was unknown. We also radio tagged 66 smallmouth bass in the Confluence reach and later detected 59 bass during mobile tracking. Predators were primarily located along shorelines in the Confluence reach, but a few fish did swim downstream into the Upper Reservoir reach. Most radio-tagged subyearlings that we determined to be dead were also located in shoreline areas suggesting that predation could account for some of the mortality we observed.

Oregon, Washington↗
USGS2010

Snake River Fall Chinook Salmon life history investigations annual report, 2009

In 2009, we used radio and acoustic telemetry to evaluate the migratory behavior, survival, mortality, and delay of subyearling fall Chinook salmon in the Clearwater River and Lower Granite Reservoir. We released a total of 1,000 tagged hatchery subyearlings at Cherry Lane on the Clearwater River in mid August and we monitored them as they passed downstream through various river and reservoir reaches. Survival through the free-flowing river was high (>0.85) for both radio- and acoustic-tagged fish, but dropped substantially as fish delayed in the Transition Zone and Confluence areas. Estimates of the joint probability of migration and survival through the Transition Zone and Confluence reaches combined were similar for both radio- and acoustic-tagged fish, and ranged from about 0.30 to 0.35. Estimates of the joint probability of delaying and surviving in the combined Transition Zone and Confluence peaked at the beginning of the study, ranging from 0.323 (SE =NA; radio-telemetry data) to 0.466 (SE =0.024; acoustic-telemetry data), and then steadily declined throughout the remainder of the study. By the end of October, no live tagged juvenile salmon were detected in either the Transition Zone or the Confluence. As estimates of the probability of delay decreased throughout the study, estimates of the probability of mortality increased, as evidenced by the survival estimate of 0.650 (SE =0.025) at the end of October (acoustic-telemetry data). Few fish were detected at Lower Granite Dam during our study and even fewer fish passed the dam before PIT-tag monitoring ended at the end of October. Five acoustic-tagged fish passed Lower Granite Dam in October and 12 passed the dam in November based on detections in the dam tailrace; however, too few detections were available to calculate the joint probabilities of migrating and surviving or delaying and surviving. Estimates of the joint probability of migrating and surviving through the reservoir was less than 0.2 based on acoustic-tagged fish. Migration rates of tagged fish were highest in the free-flowing river (median range = 36 to 43 km/d) but were generally less than 6 km/d in the reservoir reaches. In particular, median migration rates of radio-tagged fish through the Transition Zone and Confluence were 3.4 and 5.2 km/d, respectively. Median migration rate for acoustic-tagged fish though the Transition Zone and Confluence combined was 1 km/d. We radio tagged 84 smallmouth bass and six channel catfish in the Confluence reach and later detected 48 bass and 1 catfish during mobile tracking. Predators were primarily located along shorelines in the Confluence, but a couple of smallmouth bass did swim into the Clearwater River. Most radio-tagged subyearlings that we determined to be dead were also located in shoreline areas suggesting that predation could account for some of the mortality we observed. Our total dissolved gas (TDG) monitoring in the lower Clearwater River showed a cyclic pattern of low (~102%) TDG in the morning and higher (~110%) TDG in the late afternoon. Using a compensation depth of 1 m, we found that 15.4% (3.9 ha) of the lower 13 km of the Clearwater River would not provide fish with an opportunity for depth compensation in a low flow year. Water temperatures in the Clearwater River showed diel variations of about 2°C, and generally ranged from 10-12°C during summer flow augmentation. The Clearwater River generally showed little thermal variation while our tagged fish were at large, whereas the Snake River at the downstream boundary of the Confluence was thermally heterogeneous until mid-September. In the unimpounded Clearwater River, simulated water velocities ranged from about 1.3 to 1.5 m/s before flow augmentation ended, and were about 0.6 m/s thereafter. By comparison, velocities at the Clearwater River mouth were about 0.3 m/s during flow augmentation, and about 0.1 m/s thereafter. From October 2008 to February 2009 and from July 2009 to March 2010 we used monthly mobile hydroacoustic surveys to estimate the number of juvenile Chinook salmon in Little Goose and Lower Granite reservoirs, the first two reservoirs encountered on the lower Snake River by downstream migrants. Concurrent lampara seining was used to verify acoustic targets, calculate condition factors, and to examine spatial and temporal density patterns. Our data indicated that holdovers are larger in warmer water temperature years and smaller in colder water temperature years. Lampara catch data indicated that holdovers were seasonally the most abundant and in the best condition in November and December, whereas the hydroacoustic data showed population peaks in October in Lower Granite Reservoir and in January in Little Goose Reservoir. Maximum population estimates in Lower Granite Reservoir were 6,929 in October 2008 and 7,218 in October 2009. In Little Goose Reservoir, maximum population estimates were 9,645 in January 2009 and 10,419 in January 2010. By February, abundances and relative condition factors decreased as most holdovers had probably moved past Lower Granite and Little Goose dams. Spatial differences were primarily longitudinal with greater holdover abundances in the lower reaches of both reservoirs.

Report↗
USGS2010

Snake River fall Chinook salmon life history investigations, annual report 2008

In 2009, we used radio and acoustic telemetry to evaluate the migratory behavior, survival, mortality, and delay of subyearling fall Chinook salmon in the Clearwater River and Lower Granite Reservoir. We released a total of 1,000 tagged hatchery subyearlings at Cherry Lane on the Clearwater River in mid August and we monitored them as they passed downstream through various river and reservoir reaches. Survival through the free-flowing river was high (>0.85) for both radio- and acoustic-tagged fish, but dropped substantially as fish delayed in the Transition Zone and Confluence areas. Estimates of the joint probability of migration and survival through the Transition Zone and Confluence reaches combined were similar for both radio- and acoustic-tagged fish, and ranged from about 0.30 to 0.35. Estimates of the joint probability of delaying and surviving in the combined Transition Zone and Confluence peaked at the beginning of the study, ranging from 0.323 ( SE =NA; radio-telemetry data) to 0.466 ( SE =0.024; acoustic-telemetry data), and then steadily declined throughout the remainder of the study. By the end of October, no live tagged juvenile salmon were detected in either the Transition Zone or the Confluence. As estimates of the probability of delay decreased throughout the study, estimates of the probability of mortality increased, as evidenced by the survival estimate of 0.650 ( SE =0.025) at the end of October (acoustic-telemetry data). Few fish were detected at Lower Granite Dam during our study and even fewer fish passed the dam before PIT-tag monitoring ended at the end of October. Five acoustic-tagged fish passed Lower Granite Dam in October and 12 passed the dam in November based on detections in the dam tailrace; however, too few detections were available to calculate the joint probabilities of migrating and surviving or delaying and surviving. Estimates of the joint probability of migrating and surviving through the reservoir was less than 0.2 based on acoustic-tagged fish. Migration rates of tagged fish were highest in the free-flowing river (median range = 36 to 43 km/d) but were generally less than 6 km/d in the reservoir reaches. In particular, median migration rates of radio-tagged fish through the Transition Zone and Confluence were 3.4 and 5.2 km/d, respectively. Median migration rate for acoustic-tagged fish though the Transition Zone and Confluence combined was 1 km/d.

Idaho, Washington↗
USGS2009

Snake River fall Chinook salmon life history investigation, annual report 2007

In 2007, we used radio and acoustic telemetry to evaluate the migratory behavior, survival, mortality, and delay of subyearling fall Chinook salmon in the Clearwater River and Lower Granite Reservoir. Monthly releases of radio-tagged fish (~95/month) were made from May through October and releases of 122-149/month acoustic-tagged fish per month were made from August through October. We compared the size at release of our tagged fish to that which could have been obtained at the same time from in-river, beach seine collections made by the Nez Perce Tribe. Had we relied on in-river collections to obtain our fish, we would have obtained very few in June from the free-flowing river but by late July and August over 90% of collected fish in the transition zone were large enough for tagging.

Idaho, Washington↗