Download or read book Migration and Survival of Juvenile Spring Chinook Salmon and Sockeye Salmon Determined by a Large scale Telemetry Array written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis documents the use a large-scale acoustic telemetry array to track hatchery-reared salmon smolts during their seaward migration, presents estimates of early marine survival, and describes migration behaviour in the ocean of two species of Pacific salmon from the Columbia and Fraser River basins. In the Columbia River basin, it is hypothesized that seaward migrating Snake River spring Chinook salmon suffer from "delayed mortality" due to passage through eight hydropower dams or "differential delayed mortality" from transportation via barge around the dams. I tested these hypotheses by comparing survival of in-river migrating smolts from the Snake River basin to 1) a Yakima River population that migrated past only four dams and 2) a Snake River group that was transported around all dams. Early marine survival estimates of non-transported Snake and Yakima smolts from the mouth of the Columbia River to Vancouver Island (a 485 km, one month journey) was equal in both 2006 and 2008 (2007 estimates were not available), which contradicts the delayed mortality theory. Early marine survival for the transported groups was slightly higher than for the in-river migrants, again contradicting the differential delayed mortality theory. These measurements form the first direct experimental test of key theories concerning juvenile fish survival in the coastal ocean. Cultus Lake sockeye salmon are a genetically unique population from the Fraser River basin and are now endangered due to the very low return of adults in recent years. Mean survivorship of smolts (2004-7) from release to the northern Strait of Georgia ranged from 10-50%, while survivorship to the final sub-array in Queen Charlotte Strait ranged from 7-28%. Cultus Lake smolts displayed four migratory behaviours: northward migration to enter the Pacific Ocean via Queen Charlotte Strait; westward migration through the Strait of Juan de Fuca; migration into Howe Sound before continued the migration north; and migra.

Download or read book Outmigration Survival of Juvenile Spring run Chinook Salmon in Relation to Physicochemical Conditions in the San Joaquin River written by Colby Hause and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Extirpation of Central Valley spring-run Chinook salmon ESU (Oncorhynchus tshawytscha) from the San Joaquin River is emblematic of salmonid declines across the Pacific Northwest. Previous telemetry studies monitoring reintroduction of threatened spring-run Chinook salmon to the San Joaquin River revealed low out-migration survival of juveniles from rehabilitated upriver habitats to the ocean. To evaluate the link between overall habitat conditions and survivorship, we combined state-of-the-art habitat mapping approaches (Fast Automated Limnological Measurements or "FLAMe") with classic acoustic telemetry technology along the 270 km emigration corridor in Spring of 2019. We used classification algorithms on FLAMe data to develop a zonation scheme for aquatic habitats along the mainstem San Joaquin River, including a portion of the Delta. Despite elevated flow conditions in 2019, outmigration survival of smolts was again comparatively low (5%). However, our habitat-based classification scheme described variation in survival of acoustic-tagged juvenile spring-run Chinook salmon better than other candidate models based on geography or distance. Two regional mortality sinks were evident along the water quality transect, revealing poor survival in areas with higher temperatures and low levels of chlorophyll-[alpha], fDOM, and turbidity. These findings illustrate an overall value in integrating simple classification frameworks to improve our understanding of habitat variation on survival dynamics of imperiled salmonid populations.

Download or read book Marine and Freshwater Measurement of Delayed and Differential delayed Mortality of Snake River Spring Chinook Smolts Using a Continental scale Acoustic Telemetry Array written by and published by . This book was released on 2010 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Beginning in 2006, Kintama Research developed a prototype acoustic telemetry array to assess the feasibility of directly measuring movement rates and apparent survival of Snake River spring Chinook smolts in-river and northward through 1,400 km of early ocean migration. Using this array we tested the hydrosystem-induced delayed mortality hypothesis (Budy et al. 2002, Schaller and Petrosky 2007) by comparing survival of hatchery-origin spring Chinook salmon (Oncorhynchus tshawytscha) from the Snake River that migrate in-river through eight dams on their downstream migration with a mid Columbia River population (from the Yakima River) that passes through only the four lower Columbia River dams. The Yakima population has approximately four-fold higher smolt to adult return rates and thus serves as a "control" population not exposed to Snake River dam passage.

Download or read book Movement and Survival of Juvenile Chinook Salmon in California s Central Calley written by Gabriel P. Singer and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Riverine ecosystems around the world have undergone extensive anthropogenic alterations, often to the detriment of native aquatic biodiversity. Migratory fishes are particularly vulnerable to habitat fragmentation and degradation. For example, Chinook Salmon populations in the Sacramento and San Joaquin Rivers, CA have been declining for nearly a century. Its Mediterranean climate, position in a landscape dominated by urban and agricultural land use, and the presence of an inland delta that serves as the hub of California's vast water conveyance system, makes this a particularly perilous region for migrating juvenile salmon. These studies use acoustic telemetry as tool to investigate survival and routing of juvenile fall and spring-run Chinook salmon during their riverine and estuarine migratory phases in the Sacramento and San Joaquin Rivers. Survival to the ocean in these river systems is already lower relative to other Chinook Salmon populations in North American. Tracking studies included investigations of the sub-lethal effects of tagging fish with acoustic transmitters, movement ecology and survival of two distinct evolutionary significant units of Chinook Salmon during an historic drought, and the movement ecology and survival of a reintroduced population of Chinook Salmon in the San Joaquin River.

Download or read book Canadian Journal of Fisheries and Aquatic Sciences written by and published by . This book was released on 2014-05 with total page 666 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Investigations Into the Early Life History of Naturally Spring Chinook Salmon in the Grande Ronde River Basin written by and published by . This book was released on 1998 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: We determined migration timing and abundance of juvenile spring chinook salmon from three populations in the Grande Ronde River basin. We estimated 6,716 juvenile chinook salmon left upper rearing areas of the Grande Ronde River from July 1997 to June 1998; approximately 6% of the migrants left in summer, 29% in fall, 2% in winter, and 63% in spring. We estimated 8,763 juvenile chinook salmon left upper rearing areas of Catherine Creek from July 1997 to June 1998; approximately 12% of the migrants left in summer, 37% in fall, 21% in winter, and 29% in spring. We estimated 8,859 juvenile chinook salmon left the Grande Ronde Valley, located below the upper rearing areas in Catherine Creek and the Grande Ronde River, from October 1997 to June 1998; approximately 99% of the migrants left in spring. We estimated 15,738 juvenile chinook salmon left upper rearing areas of the Lostine River from July 1997 to April 1998; approximately 3% of the migrants left in summer, 61% in fall, 2% in winter, and 34% in spring. We estimated 22,754 juvenile spring chinook salmon left the Wallowa Valley, located below the mouth of the Lostine River, from September 1997 to April 1998; approximately 55% of the migrants left in fall, 5% in winter, and 40% in spring. Juvenile chinook salmon PIT-tagged on the upper Grande Ronde River were detected at Lower Granite Dam from 4 April to 26 June 1998, with a median passage date of 1 May. PIT-tagged salmon from Catherine Creek were detected at Lower Granite Dam from 3 April to 26 June 1998, with a median passage date of 8 May. PIT-tagged salmon from the Lostine River were detected at Lower Granite Dam from 31 March through 26 May 1998, with a median passage date of 28 April. Juveniles tagged as they left the upper rearing areas of the Grande Ronde and Lostine rivers in fall and that overwintered in areas downstream were detected in the hydrosystem at a higher rate than fish tagged during winter in the upper rearing areas, indicating a higher overwinter survival in the downstream areas. Fish from Catherine Creek showed no difference in detection rates between the fall and winter tag groups, indicating similar overwinter survival in the upper and lower rearing areas. Chinook salmon parr were generally associated with low velocity habitat types during winter in Catherine Creek, and both winter and summer in the Lostine River. In summer 1997, we PIT-tagged parr on Catherine Creek and the Minam and Imnaha rivers in order to monitor their subsequent migration as smolts through the Snake and Columbia River hydrosystem. We found significant differences among populations in smolt migration timing at Lower Granite Dam in 1998. Fish from Catherine Creek and the Minam and Imnaha rivers were detected in the hydrosystem at rates of 16.4, 20.5, and 28.1%, respectively. In 1998, we estimated parr abundance and the number of parr produced per redd in Catherine Creek and the Lostine River. We estimated that 429 mature, age 1+ male parr and 13,222 immature, age 0+ parr were present in Catherine Creek in August. An average of 29 mature, age 1+ male parr and 287 immature, age 0+ parr were produced from each redd constructed in 1996 and 1997, respectively. We estimated that 75 mature, age 1+ male parr and 40,748 immature, age 0+ parr were present in the Lostine River in August. An average of 3 mature, age 1+ male parr and 832 immature, age 0+ parr were produced from each redd constructed in 1996 and 1997, respectively. For every anadromous female spawner in Catherine Creek and the Lostine River in 1998, there were an estimated 13 and 3 mature male parr, respectively.

Download or read book Movements of Juvenile Chinook Salmon in the Sacramento Watershed California written by Anna Edith Steel and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Juvenile Chinook salmon (Oncorhynchus tshawytscha) experience high rates of mortality as they out-migrate, frequently navigating through rivers heavily modified by human activities. Understanding patterns of movement and survival is key to informing management decisions in these human-dominated aquatic systems. Ultrasonic telemetry is a valuable tool allowing us to observe the movement patterns of aquatic animals. The first chapter of this dissertation examines the performance of an ultrasonic telemetry positioning system by comparing receiver arrays deployed in three diverse environments. It suggests that researchers utilizing a positioning system should focus on testing the geometry of receivers before the study begins, as well as minimizing receiver movements and maximizing the accuracy of speed-of-sound estimates. The second chapter uses an ultrasonic positioning system to observe the route selection of juvenile out-migrants at an artificial juncture in the tidal portion of the Sacramento River, California. The strongest predictor of ultimate migratory route was the relative water velocity at the river's junction with the water diversion channel. The third chapter describes patterns in survival through a segment of the lower Sacramento River. We applied a previously derived analytical model, the mean free-path length model, in a new way to determine whether predator densities or prey behaviors were more indicative of fine-scale mortality rates. The model indicated that the hatchery smolt were highly directional in their outmigration behavior, leading us to conclude that spatial patterns in survival of juvenile Chinook were driven by increasing density or efficiency of the predator community. Ultrasonic telemetry technologies can be valuable in habitats where direct observation of animals is difficult, including in large river systems such as the Sacramento River. Through the continuing advancement of these technologies, their careful application, and the appropriate union of empirical data and modeling approaches, we can provide valuable information about the movements and mortality patterns of species of conservation concern.

Download or read book An Analysis of Juvenile Chinook Salmon Outmigration Speed and Survival in Response to Habitat Features Sacramento River from Knights Landing to Sacramento California written by Natalie N McNair and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Outmigration is an important life stage for Chinook salmon (Oncorhynchus tshawytscha) survival in the Sacramento River, and yet our understanding of their behavior and needs during this time is limited. To gain a better understanding of their survival and movement rates during outmigration, late fall run Chinook salmon smolts were tracked using acoustic telemetry techniques. Habitat features were measured and quantified throughout the study area to evaluate how Chinook salmon respond to key levee features including shade, instream woody material, and aquatic vegetation. The overall average movement speed through the entire study area was 0.77 m/s with an overall survival of 86%. Based on multiple linear regressions, vegetation was found to have the largest effect on speed with fish slowing down with increased vegetation cover. Shade, river mile, and velocity also had significant effects on movement speeds, but instream woody material was not significant. The result for woody material was surprising since it was anticipated to have a large impact on movement speeds. A positive correlation was found between faster fish movement speeds and higher survival. No evidence of diel movement patterns was found after releasing the fish. These finding can help managers create sites better designed to help Chinook salmon in the Sacramento River system. Results from this paper indicate that the type of woody material being installed might not be appropriate for this life stage of salmon.

Download or read book Monitoring the Migrations of Wild Snake River Spring Summer Chinook Salmon Juveniles 2003 2004 Annual Report written by Stephen Achord and published by . This book was released on 2005 with total page 97 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report provides information on PIT-tagging of wild Chinook salmon parr in Idaho in 2003 and the subsequent monitoring of these fish and similarly tagged fish from Oregon. We report estimated parr-to-smolt survival and arrival timing of these fish at Lower Granite Dam, as well as interrogation data collected at several other sites throughout the Snake and Columbia River system. This research continues studies that began under Bonneville Power Administration (BPA) funding in 1991. Results from previous study years were reported by Achord et al. (1994; 1995a, b; 1996a; 1997; 1998; 2000; 2001a, b; 2002, 2003, 2004). Goals of this ongoing study are: (1) Characterize the migration timing and estimate parr-to-smolt survival of different stocks of wild Snake River spring/summer Chinook salmon smolts at Lower Granite Dam. (2) Determine whether consistent migration patterns are apparent. (3) Determine what environmental factors influence migration patterns. (4) Characterize the migration behavior and estimate survival of different wild juvenile fish stocks as they emigrate from their natal rearing areas. This study provides critical information for recovery planning, and ultimately recovery for these ESA-listed wild fish stocks. In 2003-2004, we also continued to measure water temperature, dissolved oxygen, specific conductance, turbidity, water depth, and pH at five monitoring stations in the Salmon River Basin, Idaho for the Baseline Environmental Monitoring Program. These data, along with parr/smolt migration, survival, and timing data, will help to discern patterns or characteristic relationships between fish movement/survival and environmental factors.

Download or read book Migratory Characteristics of Juvenile Spring Chinook Salmon in the Willamette River written by and published by . This book was released on 1994 with total page 121 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this research was to examine in detail the migration of juvenile spring chinook salmon (Oncorhynchus tshawytscha) in the Willamette River, Oregon. The authors wanted to determine characteristics of seaward migration of spring chinook smolts in relation to the oxygen supplementation practices at the Oregon Department of Fish and Wildlife (ODFW) Willamette Hatchery and use this information to strengthen the design of the oxygen supplementation project. There is little information available on the effects of oxygen supplementation at hatcheries on the migratory characteristics of juvenile salmon. Such information is required to assess the use of oxygen supplementation as a means of improving hatchery production, its effect on imprinting of juveniles, and finally the return of adults. In the event that oxygen supplementation provides for improved production and survival of juvenile chinook salmon at Willamette Hatchery, background information on the migration characteristics of these fish will be required to effectively utilize the increased production within the goals of the Willamette Fish Management Plan. Furthermore this technology may be instrumental in the goal of doubling the runs of spring Chinook salmon in the Columbia River. While evaluation of success is dependent on evaluation of the return of adults with coded wire tags, examination of the migratory characteristics of hatchery smolts may prove to be equally informative. Through this research it is possible to determine the rate at which individuals from various oxygenation treatment groups leave the Willamette River system, a factor which may be strongly related to adult return rate.

Download or read book Acoustic Telemetry Studies of Juvenile Chinook Salmon Survival at the Lower Columbia Projects in 2006 written by Gene R. Ploskey and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Year class Regulation of Mid upper Columbia River Spring Chinook Salmon Oncorhynchus Tshawytscha written by Londi M. Tomaro and published by . This book was released on 2011 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt: Early ocean residence is assumed to be a critical period for juvenile Pacific salmon Oncorhynchus spp. However, the specific mechanisms influencing growth and survival in the ocean have not been identified for most populations. Therefore, three hypotheses regarding the relationship between early marine residence and subsequent survival of mid-upper Columbia River spring Chinook salmon were evaluated: the 'bigger is better', 'stage duration', and 'match-mistmatch' hypotheses. Six metrics describing juvenile migration history and condition were developed, including 1) size at freshwater exit; 2) size at ocean capture; 3) initial ocean growth rates; 4) timing of ocean entrance; 5) duration of ocean residence; and 6) marine migration rates. Retrospective estimates of size and growth using otolith analyses rely on the assumption that otolith and somatic size are related. Therefore, I verified this assumption for mid-upper Columbia River Chinook salmon and determined that a body-proportional back-calculation method was the best approach for this population. Fish length and otolith width were positively correlated (r > 0.92) and growth rates estimated from back-calculated sizes were positively correlated with observed growth rates (r = 0.96). I also evaluated the utility of using the otolith Sr:Ca pattern as a marker of hatchery-origin and investigated potential mechanisms for the observed Sr:Ca pattern. Visual and quantitative criteria were developed using otoliths of hatchery fish and were used to correctly classify 85% and 78%, respectively, of a sample of known hatchery-origin fish (n = 114) that were collected in coastal waters. Although Sr:Ca in water and hatchery food did not fully account for the observed pattern in otolith Sr:Ca, the pattern can be used to identify mid-upper Columbia River spring Chinook salmon of hatchery-origin with relatively high accuracy (>75%). The six juvenile metrics were used to evaluate mechanisms potentially regulating establishment of year-class abundance. The only metrics found to be significantly related to future adult abundance were size at freshwater exit (r2 = 0.56) and capture (r2 = 0.60). These data support the 'bigger is better' hypothesis and indicate that factors influencing size and growth during freshwater residence should be investigated further. Juveniles resided in the brackish/ocean for one to two months prior to capture in May and June; therefore, ocean conditions after this period may be related to the 40% of variation in adult abundance unexplained by interannual variation in body size.

Download or read book Comparing the Survival Rate of Juvenile Chinook Salmon Migrating Through Hydropower Systems Using Injectable and Surgical Acoustic Transmitters written by and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Acoustic telemetry is one of the primary technologies for studying the behavior and survival of fishes throughout the world. The size and performance of the transmitters is still the key limiting factor despite that considerable effort has been expended to understand the biological effects of implantation of acoustic transmitters in yearling and subyearling Chinook salmon. The newly developed injectable transmitter is the first active acoustic tag that can be implanted via injection instead of surgery. It also lasts more than four times longer than the commercially-available transmitters. A two-part field study was conducted to evaluate the performance of the injectable transmitter and its effect on the survival of implanted fish. The injectable transmitter performed well and similarly to the other commercially-available transmitters tested. Snake River subyearling Chinook salmon smolts implanted with the injectable tag had a higher survival probability from release to each of 11 downstream detection arrays than concurrent releases of fish surgically implanted with commercially-available tags. In addition, reach-specific survival estimates were significantly higher for the injectable group in three of the eleven reaches examined. Overall, the injectable group had a 0.263 (SE = 0.017) survival probability over the entire 500 km study area compared to 0.199 (0.012) for the surgically implanted group. The differences in survival may have been caused by warm water temperatures and higher rates of infection experienced by the surgically implanted group due to the presence of sutures acting as an attachment site for pathogens. The reduction in size and ability to implant the new transmitter via injection has further reduced the tag or tagging effect bias associated with studying small fishes. As a result, the information gathered with this new technology is helping minimize the impact of dams on fish, leading to more environmentally sustainable energy systems.

Download or read book Temperature Timing and Seaward Migration of Juvenile Chinook Salmon from the Central Columbia River written by Clarence Dale Becker and published by . This book was released on 1970 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Death of a Salmon written by Ian Geoffrey Brosnan and published by . This book was released on 2014 with total page 366 pages. Available in PDF, EPUB and Kindle. Book excerpt: From 2008 to 2011, migrating acoustic-tagged juvenile yearling Chinook salmon smolts (Oncorhynchus tshawytscha) were detected on receivers deployed across the Columbia River and continental shelf at Cascade Head (Oregon), Willapa Bay (Washington), and Vancouver Island (British Columbia). The telemetry data were used to estimate survival and record migration parameters. These were evaluated against oceanographic and freshwater hydrologic variables in statistical and individual-based models. Plume survival was found to be variable, but daily survival rates were more constant and survival was effectively modeled as exponential decay. Correlates of early marine survival that do not have direct effects may act on plume survival by controlling the period of exposure to plume predation. In 2011, half of smolts released were exposed to total dissolved gas levels (TDG) above 120%, the water quality limit for TDG below Columbia River dams. This exposure appears to have negatively affected daily survival rates in the lower river and plume, and has important implications for a proposal to increase the TDG limit to 125% to support spring fish passage. Finally, consistent with the critical size, critical period hypothesis of salmon production, it appears that smolts select habitat to maximize their growth as they migrate north through the plume, rather than selectively using local currents to speed their passage. These findings shed new light on perennial questions in salmon early marine ecology. They lay the groundwork for future research aimed at understanding the effects of changing oceanography and freshwater hydrology on salmon migration and survival.

Download or read book Ecological Drivers of Variation in Juvenile Sockeye Salmon Marine Migrations written by Cameron Freshwater and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Animal migrations are often associated with high mortality due to increased energy expenditure, reduced foraging opportunities, and increased predation risk. Migratory traits such as body size, phenology, or use of stopover habitats may moderate individual risk to mortality mechanisms and influence patterns of survival. However, variability in migratory traits is rarely quantified in detail because tracking many individuals over large areas is logistically challenging. In this dissertation, I used otoliths to examine migratory variability among and within sockeye salmon (Oncorhynchus nerka) populations, a species that has recently experienced declines associated with poor survival during juvenile marine migrations. Broadly, I examined the individual and environmental drivers of migratory patterns, as well as how variation across ecological scales (individuals, populations, and years) contributed to migratory diversity. First, I conducted a laboratory study to validate the use of otolith microstructure techniques in sockeye salmon post-smolts. Next, I assessed how a suite of ecological processes could interact to create a latitudinal gradient in sockeye salmon body size. By reconstructing individual growth and migration histories I determined that variation in size was correlated with ocean entry size and phenology, rather than differential marine growth or size-selective mortality. I then used estimates of migratory rate from otoliths to demonstrate that juvenile sockeye salmon exhibited distinct migratory phenotypes associated with ocean entry traits. Larger individuals migrated rapidly offshore, while smaller fish reared for several weeks in nearshore regions. Furthermore, a subset of the smallest individuals entered the ocean late in the year, migrated particularly slowly, and may have overwintered on the continental shelf. These linkages between ocean entry and migratory traits suggest juvenile sockeye salmon exhibit substantial migratory plasticity associated with carry-over effects from freshwater residence; however juvenile salmon may also respond strongly to variable conditions in marine habitats. In my fifth chapter, I compared marine growth and migration phenology in years with low and high competitor densities. After accounting for freshwater density-dependent effects, growth rates were similar in both years, but mean migration rates were nearly 50% faster in the high-density year. Migratory behavior may be used to buffer individuals from the effect of competitive interactions. In my final chapter, I sampled 16 Fraser River sockeye salmon populations to explore variation in the timing and duration of early marine migrations. Although populations differed in downstream migration timing, as well as their duration of residence within nearshore habitats, there was substantial variation within each population and between sampling years. These findings suggest individual characteristics and stochastic processes interact with population-specific strategies to shape migratory phenologies in this metapopulation. Management actions should account for and preserve migratory diversity at multiple ecological scales to maintain resilient salmon populations into the future.

Download or read book Fine scale Structure in the Ecology of Juvenile Chinook Salmon at Sea written by William Duguid and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Fisheries oceanography often aims to link large scale atmospheric and oceanic processes to variability and trends in the productivity of economically and ecologically valuable fish species. Declines in productivity of multiple species of Pacific Salmon (genus Oncorhynchus) in recent decades have spurred the search for a 'smoking gun;' an explanation that could explain trends in productivity across populations, regions and species. Despite extensive investment of research effort and funding, such an explanation remains elusive. The lack of a unifying explanation for declining productivity of Pacific Salmon may be due to the spatial and temporal complexity of their interactions with the marine environment. This complexity has historically been understudied, in part due to logistical limitations of research on Pacific Salmon at sea. This dissertation reports the results of a detailed study of how juvenile Chinook Salmon O. tshawytscha interact with marine habitats during their first summer and fall at sea. I first developed and validated a novel, hook and line-based method of sampling juvenile Chinook Salmon (microtrolling). I then reviewed and empirically compared methods (insulin like growth factor-1 concentration, RNA to DNA ratio, and scale circulus spacing) for indexing growth rate of juvenile salmon sampled in the ocean, a variable which is hypothesized to be related to subsequent survival. I integrated microtrolling with small vessel oceanography to relate distribution, diet, size and growth of juvenile Chinook Salmon to local scale variation in water column properties (stratification) and zooplankton community composition and abundance for five sites in the Southern Gulf Islands of the Salish Sea during a single summer (2015). While both stratification and zooplankton abundance and composition varied between sites, I failed to find support for the hypothesis that juvenile salmon distribution and growth was positively related to water column stratification at fine spatial scales. Juvenile Chinook Salmon were larger and faster growing where juvenile Pacific Herring Clupea pallasii were important in their diets, suggesting that Pacific Herring may play an important role in structuring the ecology of juvenile Chinook Salmon at sea. I built on 2015 results to conduct a detailed case study of juvenile Chinook Salmon ecology at two sites in the Southern Gulf Islands: Sansum Narrows and Maple Bay. Juvenile Chinook Salmon were consistently larger, more piscivorous, and faster growing at Sansum Narrows than Maple Bay across two years (2015 and 2016) despite lower zooplankton abundance at Sansum Narrows. Hydroacoustic surveys in September 2017 confirmed prior qualitative observations of elevated occurrence of forage fish schools (likely age-0 Pacific Herring) at Sansum Narrows, and a novel, mobile acoustic tag tracking survey suggested that fish tagged at Sansum Narrows may co-locate with juvenile Pacific Herring over the tidal cycle. By relating a scale circulus spacing-based growth index to reconstructed size intervals I found that juvenile Chinook Salmon at Sansum Narrows had been faster growing that those at Maple Bay before the transition to piscivory, and perhaps before migration to the ocean. These results suggest that intrinsic growth potential, or growth conditions during freshwater rearing or the transition to marine residence, interact with fine-scale structure in marine habitats to regulate growth potential of juvenile Chinook Salmon at sea. These factors also likely interact with the basin and interannual scale processes that have received extensive study as regulators of marine survival of juvenile Pacific salmon. These complex interactions should be taken into account when designing or interpreting studies to determine factors limiting productivity of Pacific Salmon populations.