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• 11. [Article] Pinniped and seabird predation: implications for recovery of threatened stocks of salmonids in Oregon under the Oregon Plan for Salmon and Watersheds

  This report was written by the Independent Multidisciplinary Science Team of the Oregon Plan for Salmon and Watersheds.

  Citation × Citation Citation Abstract Copy Title: Pinniped and seabird predation: implications for recovery of threatened stocks of salmonids in Oregon under the Oregon Plan for Salmon and Watersheds Author: Independent Multidisciplinary Science Team (Or.) This report was written by the Independent Multidisciplinary Science Team of the Oregon Plan for Salmon and Watersheds. Title: Pinniped and seabird predation: implications for recovery of threatened stocks of salmonids in Oregon under the Oregon Plan for Salmon and Watersheds Author: Independent Multidisciplinary Science Team (Or.) This report was written by the Independent Multidisciplinary Science Team of the Oregon Plan for Salmon and Watersheds. Close

• 12. [Article] Juvenile Salmonid Use of Freshwater Emergent Wetlands in the Floodplain and Its Implications for Conservation Management

  A recent trend of enhancing freshwater emergent wetlands for waterfowl and other wildlife has raised concern about the effects of such measures on juvenile salmonids. We undertook this study to quantify ...

  Citation × Citation Citation Abstract Copy Title: Juvenile Salmonid Use of Freshwater Emergent Wetlands in the Floodplain and Its Implications for Conservation Management Author: Gresswell, Robert E., Fleming, Ian A., Henning, Julie A. A recent trend of enhancing freshwater emergent wetlands for waterfowl and other wildlife has raised concern about the effects of such measures on juvenile salmonids. We undertook this study to quantify the degree and extent of juvenile Pacific salmon Oncorhynchus spp. utilization of enhanced and unenhanced emergent wetlands within the floodplain of the lower Chehalis River, Washington, and to determine the fate of the salmon using them. Enhanced emergent wetlands contained water control structures that provided an outlet for fish emigration and a longer hydroperiod for rearing than unenhanced wetlands. Age-0 and age-1 coho salmon O. kisutch were the most common salmonid at all sites, enhanced wetlands having significantly higher age-1 abundance than unenhanced wetlands that were a similar distance from the main-stem river. Yearling coho salmon benefited from rearing in two enhanced wetland habitats, where their specific growth rate and minimum estimates of survival (1.43%/d by weight and 30%; 1.37%/d and 57%) were comparable to those in other side-channel rearing studies. Dissolved oxygen concentrations decreased in emergent wetlands throughout the season and approached the limits lethal to juvenile salmon by May or June each year. Emigration patterns suggested that age-0 and age-1 coho salmon emigrated as habitat conditions declined. This observation was further supported by the results of an experimental release of coho salmon. Survival of fish utilizing emergent wetlands was dependent on movement to the river before water quality decreased or stranding occurred from wetland desiccation. Thus, our results suggest that enhancing freshwater wetlands via water control structures can benefit juvenile salmonids, at least in the short term, by providing conditions for greater growth, survival, and emigration. Title: Juvenile Salmonid Use of Freshwater Emergent Wetlands in the Floodplain and Its Implications for Conservation Management Author: Gresswell, Robert E., Fleming, Ian A., Henning, Julie A. A recent trend of enhancing freshwater emergent wetlands for waterfowl and other wildlife has raised concern about the effects of such measures on juvenile salmonids. We undertook this study to quantify the degree and extent of juvenile Pacific salmon Oncorhynchus spp. utilization of enhanced and unenhanced emergent wetlands within the floodplain of the lower Chehalis River, Washington, and to determine the fate of the salmon using them. Enhanced emergent wetlands contained water control structures that provided an outlet for fish emigration and a longer hydroperiod for rearing than unenhanced wetlands. Age-0 and age-1 coho salmon O. kisutch were the most common salmonid at all sites, enhanced wetlands having significantly higher age-1 abundance than unenhanced wetlands that were a similar distance from the main-stem river. Yearling coho salmon benefited from rearing in two enhanced wetland habitats, where their specific growth rate and minimum estimates of survival (1.43%/d by weight and 30%; 1.37%/d and 57%) were comparable to those in other side-channel rearing studies. Dissolved oxygen concentrations decreased in emergent wetlands throughout the season and approached the limits lethal to juvenile salmon by May or June each year. Emigration patterns suggested that age-0 and age-1 coho salmon emigrated as habitat conditions declined. This observation was further supported by the results of an experimental release of coho salmon. Survival of fish utilizing emergent wetlands was dependent on movement to the river before water quality decreased or stranding occurred from wetland desiccation. Thus, our results suggest that enhancing freshwater wetlands via water control structures can benefit juvenile salmonids, at least in the short term, by providing conditions for greater growth, survival, and emigration. Close

• 13. [Article] Geospatial depiction of spring 2009 Chinook Salmon runs for Wallowa County, Oregon

  This product is for informational purposes and may not have been prepared for, or be suitable for legal, engineering, or surveying purposes. Users of this information should review or consult the primary ...

  Citation × Citation Citation Abstract Copy Title: Geospatial depiction of spring 2009 Chinook Salmon runs for Wallowa County, Oregon Author: Thomas, Samuel, Oregon State University, Department of Fish and Wildlife, State of Oregon This product is for informational purposes and may not have been prepared for, or be suitable for legal, engineering, or surveying purposes. Users of this information should review or consult the primary data and information sources to verify the purpose and limitations. The data is provided as-is, without warranty. Title: Geospatial depiction of spring 2009 Chinook Salmon runs for Wallowa County, Oregon Author: Thomas, Samuel, Oregon State University, Department of Fish and Wildlife, State of Oregon This product is for informational purposes and may not have been prepared for, or be suitable for legal, engineering, or surveying purposes. Users of this information should review or consult the primary data and information sources to verify the purpose and limitations. The data is provided as-is, without warranty. Close

• 14. [Article] Kodiak brown bears surf the salmon red wave: direct evidence from GPS collared individuals

  To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The article is copyrighted by the Ecological ...

  Citation × Citation Citation Abstract Copy Title: Kodiak brown bears surf the salmon red wave: direct evidence from GPS collared individuals Author: Leacock, William, Stanford, Jack A., Deacy, William, Armstrong, Jonathan B. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The article is copyrighted by the Ecological Society of America and published by John Wiley & Sons, Inc. It can be found at: http://esajournals.onlinelibrary.wiley.com/hub/journal/10.1002/%28ISSN%291939-9170/ Title: Kodiak brown bears surf the salmon red wave: direct evidence from GPS collared individuals Author: Leacock, William, Stanford, Jack A., Deacy, William, Armstrong, Jonathan B. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The article is copyrighted by the Ecological Society of America and published by John Wiley & Sons, Inc. It can be found at: http://esajournals.onlinelibrary.wiley.com/hub/journal/10.1002/%28ISSN%291939-9170/ Close

• 15. [Article] Investigating Demographic and Evolutionary Factors Important for Fish Reintroduction

  Reintroduction programs are used to re-establish species back into their historical habitat. Most reintroduction programs have failed and few papers have evaluated factors that may be important to Pacific ...

  Citation × Citation Citation Abstract Copy Title: Investigating Demographic and Evolutionary Factors Important for Fish Reintroduction Author: Sard, Nicholas M. Reintroduction programs are used to re-establish species back into their historical habitat. Most reintroduction programs have failed and few papers have evaluated factors that may be important to Pacific salmon. The 158 meter tall Cougar Dam has blocked Chinook salmon (Oncorhynchus tshawytscha) from accessing 40 kilometers of historical spawning and rearing habitat for over 50 years. Here, I evaluated a Chinook salmon trap and transport reintroduction program above Cougar Dam on the South Fork McKenzie River, Oregon from 2007 to 2015. First, I evaluated if release location and date correlated with two measures of fitness based on adult assignments to age-0 juveniles collected above the dam and adult offspring returning to the South Fork McKenzie River, respectively. I found that release location and date had little to no effect on either measure of fitness. I also evaluated if there were fitness differences between hatchery and natural origin (HOR and NOR, respectively) adults. I found consistent fitness differences between males (RRS=0.48, p<0.001), but not females (RRS=0.72, p=0.81). In addition, I found that origin (p=0.352) no longer explained variation in fitness after accounting for variation in fork-length, which suggests that HOR fish may be less fit, in part, because they are 2-4 cm (95% CI) smaller, or perhaps younger. I also evaluated a measure of population productivity known as cohort replacement rate (CRR) - defined as the number of future spawners produced by a spawner. Based on genetic parentage assignments to NOR adults returning to the trap and transport facility, hereafter Cougar Trap, I found that adults reintroduced in 2007 and 2008 did not meet demographic replacement (CRR: 0.40 and 0.31, respectively). I also found a seasonal decline in the proportion of NOR adults produced above the dam that returned to the Cougar Trap. I also developed grandparentage assignment methods to determine how many precocial males and adfluvial Chinook salmon, two non-anadromous life history tactics, contributed to population productivity. I found 31 unsampled precocial males, as well as 48 age-4 and -5 probable adfluvial male and female adults contributed to the reintroduced population. My discovery of adfluvial Chinook salmon contributing to population productivity is significant because little is known about this life history tactic, and they provide resiliency to a reintroduced population. I show that adfluvial adults can be produced by anadromous mate pairs. Adfluvial adults increased CRR estimates; however, neither the 2007 or 2008 cohorts met replacement after incorporating this non-anadromous life history tactic (CRR: 0.46 and 0.35, respectively). Finally, I assessed if genetic variation in founding cohorts was maintained in their returning adult offspring returning to the South Fork McKenzie River, hereafter F₁ offspring. On average, 6 alleles were lost per locus between founding cohorts and their F₁ offspring. N[subscript e] estimates were high using either demographic or genetic methods (range: 344 to 893). My dissertation research provides valuable information on factors that may be important to population productivity, as well as the maintenance of genetic variation in nascent populations established through reintroduction. Title: Investigating Demographic and Evolutionary Factors Important for Fish Reintroduction Author: Sard, Nicholas M. Reintroduction programs are used to re-establish species back into their historical habitat. Most reintroduction programs have failed and few papers have evaluated factors that may be important to Pacific salmon. The 158 meter tall Cougar Dam has blocked Chinook salmon (Oncorhynchus tshawytscha) from accessing 40 kilometers of historical spawning and rearing habitat for over 50 years. Here, I evaluated a Chinook salmon trap and transport reintroduction program above Cougar Dam on the South Fork McKenzie River, Oregon from 2007 to 2015. First, I evaluated if release location and date correlated with two measures of fitness based on adult assignments to age-0 juveniles collected above the dam and adult offspring returning to the South Fork McKenzie River, respectively. I found that release location and date had little to no effect on either measure of fitness. I also evaluated if there were fitness differences between hatchery and natural origin (HOR and NOR, respectively) adults. I found consistent fitness differences between males (RRS=0.48, p<0.001), but not females (RRS=0.72, p=0.81). In addition, I found that origin (p=0.352) no longer explained variation in fitness after accounting for variation in fork-length, which suggests that HOR fish may be less fit, in part, because they are 2-4 cm (95% CI) smaller, or perhaps younger. I also evaluated a measure of population productivity known as cohort replacement rate (CRR) - defined as the number of future spawners produced by a spawner. Based on genetic parentage assignments to NOR adults returning to the trap and transport facility, hereafter Cougar Trap, I found that adults reintroduced in 2007 and 2008 did not meet demographic replacement (CRR: 0.40 and 0.31, respectively). I also found a seasonal decline in the proportion of NOR adults produced above the dam that returned to the Cougar Trap. I also developed grandparentage assignment methods to determine how many precocial males and adfluvial Chinook salmon, two non-anadromous life history tactics, contributed to population productivity. I found 31 unsampled precocial males, as well as 48 age-4 and -5 probable adfluvial male and female adults contributed to the reintroduced population. My discovery of adfluvial Chinook salmon contributing to population productivity is significant because little is known about this life history tactic, and they provide resiliency to a reintroduced population. I show that adfluvial adults can be produced by anadromous mate pairs. Adfluvial adults increased CRR estimates; however, neither the 2007 or 2008 cohorts met replacement after incorporating this non-anadromous life history tactic (CRR: 0.46 and 0.35, respectively). Finally, I assessed if genetic variation in founding cohorts was maintained in their returning adult offspring returning to the South Fork McKenzie River, hereafter F₁ offspring. On average, 6 alleles were lost per locus between founding cohorts and their F₁ offspring. N[subscript e] estimates were high using either demographic or genetic methods (range: 344 to 893). My dissertation research provides valuable information on factors that may be important to population productivity, as well as the maintenance of genetic variation in nascent populations established through reintroduction. Close

• 16. [Article] Recovery of wild salmonids in western Oregon forests: Oregon Forest Practices Act rules and the measures in the Oregon Plan for Salmon and Watersheds

  This report and addendum was written by the Independent Multidisciplinary Science Team of the Oregon Plan for Salmon and Watersheds

  Citation × Citation Citation Abstract Copy Title: Recovery of wild salmonids in western Oregon forests: Oregon Forest Practices Act rules and the measures in the Oregon Plan for Salmon and Watersheds Author: Independent Multidisciplinary Science Team (Or.) This report and addendum was written by the Independent Multidisciplinary Science Team of the Oregon Plan for Salmon and Watersheds Title: Recovery of wild salmonids in western Oregon forests: Oregon Forest Practices Act rules and the measures in the Oregon Plan for Salmon and Watersheds Author: Independent Multidisciplinary Science Team (Or.) This report and addendum was written by the Independent Multidisciplinary Science Team of the Oregon Plan for Salmon and Watersheds Close

• 17. [Article] Umpqua Coho Salmon Genetic Pedigree

  Suggested citation: "Blouin, Michael S.; Banks, Michael A.; Moyer, Gregory R.; Theriault, Veronique; Whitcomb, Amelia; Loomis, David; Jackson, Laura S. (2013): Umpqua Coho Salmon Genetic Pedigree. Oregon ...

  Citation × Citation Citation Abstract Copy Title: Umpqua Coho Salmon Genetic Pedigree Author: Blouin, Michael S., Jackson, Laura S., Loomis, David, Theriault, Veronique, Moyer, Gregory R., Whitcomb, Amelia, Banks, Michael A. Suggested citation: "Blouin, Michael S.; Banks, Michael A.; Moyer, Gregory R.; Theriault, Veronique; Whitcomb, Amelia; Loomis, David; Jackson, Laura S. (2013): Umpqua Coho Salmon Genetic Pedigree. Oregon State University Libraries. Dataset. doi:10.7267/N9H41PB9." Title: Umpqua Coho Salmon Genetic Pedigree Author: Blouin, Michael S., Jackson, Laura S., Loomis, David, Theriault, Veronique, Moyer, Gregory R., Whitcomb, Amelia, Banks, Michael A. Suggested citation: "Blouin, Michael S.; Banks, Michael A.; Moyer, Gregory R.; Theriault, Veronique; Whitcomb, Amelia; Loomis, David; Jackson, Laura S. (2013): Umpqua Coho Salmon Genetic Pedigree. Oregon State University Libraries. Dataset. doi:10.7267/N9H41PB9." Close

• 18. [Article] Turning Points in the Development of the British Columbia Salmon Fishery

  Research Paper

  Citation × Citation Citation Abstract Copy Title: Turning Points in the Development of the British Columbia Salmon Fishery Author: Millerd, Frank Research Paper Title: Turning Points in the Development of the British Columbia Salmon Fishery Author: Millerd, Frank Research Paper Close

• 19. [Article] DNA-based identification of commercially important salmon and trout species (genera Oncorhynchus and Salmo) in North America

  There are seven commercially important species of salmon and trout (genera Oncorhynchus and Salmo) in North America, many of which are closely related but command markedly different prices. The purpose ...

  Citation × Citation Citation Abstract Copy Title: DNA-based identification of commercially important salmon and trout species (genera Oncorhynchus and Salmo) in North America Author: Rasmussen, Rosalee S. There are seven commercially important species of salmon and trout (genera Oncorhynchus and Salmo) in North America, many of which are closely related but command markedly different prices. The purpose of this research was to provide improved and novel methods for the detection of salmon species substitution on the commercial market. This work took place in three parts: first an existing method was optimized and improved upon, then a comprehensive collection of reference salmon sequences was built for use in species identification with DNA barcoding, and finally, based on these sequences, a novel species-specific multiplex polymerase chain reaction (PCR) assay was developed. In the first study, a PCR-restriction fragment length polymorphism (RFLP) method for salmon species identification was optimized for use with U.S. commercial products. The restriction digest was shortened to 1 h rather than overnight and the method was successful with lightly processed products. However, heavily processed samples could not be identified. Next, DNA barcoding was examined as a method for salmon species identification. Sequence information was collected for 924 reference samples from a wide geographic range. Sequences showed low intraspecies divergences (mean 0.26%), and the mean congeneric divergence was 32-fold greater, at 8.22%. The minimum interspecies divergence was always greater than the maximum intraspecies divergence, indicating that these species can be differentiated using DNA barcodes. In the next study, species-specific primers and probes were developed based on DNA barcode sequence information to diagnose salmon species in both real-time and conventional PCR systems. The primers and probes were combined into multiplex assays and tested for specificity against 94-112 reference samples representing 19-25 species. Strong signals were detected for the target species in both systems, and nonspecific amplification was minimal. Both assays showed high sensitivity, with detection levels of 0.05 to 5.0 ng (0.1 to 10% in DNA admixtures). Overall, this study presents a rapid, specific and sensitive method for salmon species identification that can be applied to mixed-species and heavily processed samples in either a conventional or real-time format. Title: DNA-based identification of commercially important salmon and trout species (genera Oncorhynchus and Salmo) in North America Author: Rasmussen, Rosalee S. There are seven commercially important species of salmon and trout (genera Oncorhynchus and Salmo) in North America, many of which are closely related but command markedly different prices. The purpose of this research was to provide improved and novel methods for the detection of salmon species substitution on the commercial market. This work took place in three parts: first an existing method was optimized and improved upon, then a comprehensive collection of reference salmon sequences was built for use in species identification with DNA barcoding, and finally, based on these sequences, a novel species-specific multiplex polymerase chain reaction (PCR) assay was developed. In the first study, a PCR-restriction fragment length polymorphism (RFLP) method for salmon species identification was optimized for use with U.S. commercial products. The restriction digest was shortened to 1 h rather than overnight and the method was successful with lightly processed products. However, heavily processed samples could not be identified. Next, DNA barcoding was examined as a method for salmon species identification. Sequence information was collected for 924 reference samples from a wide geographic range. Sequences showed low intraspecies divergences (mean 0.26%), and the mean congeneric divergence was 32-fold greater, at 8.22%. The minimum interspecies divergence was always greater than the maximum intraspecies divergence, indicating that these species can be differentiated using DNA barcodes. In the next study, species-specific primers and probes were developed based on DNA barcode sequence information to diagnose salmon species in both real-time and conventional PCR systems. The primers and probes were combined into multiplex assays and tested for specificity against 94-112 reference samples representing 19-25 species. Strong signals were detected for the target species in both systems, and nonspecific amplification was minimal. Both assays showed high sensitivity, with detection levels of 0.05 to 5.0 ng (0.1 to 10% in DNA admixtures). Overall, this study presents a rapid, specific and sensitive method for salmon species identification that can be applied to mixed-species and heavily processed samples in either a conventional or real-time format. Close

• 20. [Article] Juvenile coho salmon movement and migration through tide gates

  Tidal marshlands in the upper estuary ecotone provide essential habitat for juvenile salmonids. In this environment, salmonids grow rapidly and acclimate to saltwater. Worldwide, tidal marshes have been ...

  Citation × Citation Citation Abstract Copy Title: Juvenile coho salmon movement and migration through tide gates Author: Bass, Arthur Langer Tidal marshlands in the upper estuary ecotone provide essential habitat for juvenile salmonids. In this environment, salmonids grow rapidly and acclimate to saltwater. Worldwide, tidal marshes have been diked and drained to provide agricultural and residential land. Tide gates are one-way doors integrated into dike systems that prevent saltwater flooding and allow upland drainage to the estuary during low tide. By preventing tidal exchange, tide gates have significant upstream effects on water temperature and chemistry, plant and animal community structure, and geomorphology. Since they are closed most of the day and may be difficult to pass when open, tide gates may act as fish passage barriers for juvenile salmonids. They may also affect juvenile salmon migration timing by altering environmental variables that influence emigration rate in upstream habitats. We conducted our research in Coos Bay, one of the many Oregon estuaries with extensive use of tide gates. We studied three streams, one with a top-hinged tide gate, one with a side-hinged gate, and one without any tide gates that acted as our reference site. Our study species was coho salmon, Oncorhynchus kisutch, which may encounter tide gates both in the subyearling and smolt life stages in our study streams. Our objectives were to: 1) quantify upstream and downstream fish passage occurrence at all three sites, 2) determine whether juvenile coho salmon passage is associated with a specific range of gate conditions, and 3) identify any associations between coho smolt emigration rate and environmental variables that are influenced by tide gates. We installed stationary passive integrated transponder (PIT) antennae around both tide gates and a tidal channel in the non-gated stream to record the movement of PIT tagged juvenile coho salmon. Coho salmon smolts passed upstream most frequently at the non-gated channel (48% of all smolts detected at the array), next the side-hinged gate (28%), and lastly, the top-hinged gate (3%). Juvenile coho salmon passed more frequently at a specific range of gate angles and tailwater depths at both top hinged and side-hinged tide gates. Smolts passed downstream more frequently at greater gate angles and tailwater depths than available on average at both tide gates. Subyearlings passed upstream more frequently during small gate angles and a narrow range of tailwater depths at the top-hinged gate but did not pass more frequently under a particular range of conditions at the side-hinged gate. At the top-hinged gate, conditions favorable for subyearling upstream passage occurred towards the end of the gate open period and therefore subyearlings were severely limited in their opportunities for passage. At multiple sites, emigration rate was associated with environmental variables that may be altered by tide gates. Increases in water temperature were associated with an increasing likelihood of smolt emigration at multiple sites. At a tide gate that allowed upstream estuarine influence, increasing salinity was associated with a decreasing likelihood of emigration. Our results suggest that tide gates may interfere with salmonid movement and migration by creating physical barriers to fish passage and potentially influencing migratory timing by altering environmental variables. When installing or retrofitting tide gates, these factors should be taken into consideration since a tide gate's design may determine the severity of its effects on salmonids. Our work should be considered a case study and the findings should not be assumed to be transferable due to the great diversity of tide gate installations in use. We recommend further research, including a more in depth analysis of the affects of tide gates on subyearling coho salmon and an investigation of piscivorous predator exploitation of tide gates. Title: Juvenile coho salmon movement and migration through tide gates Author: Bass, Arthur Langer Tidal marshlands in the upper estuary ecotone provide essential habitat for juvenile salmonids. In this environment, salmonids grow rapidly and acclimate to saltwater. Worldwide, tidal marshes have been diked and drained to provide agricultural and residential land. Tide gates are one-way doors integrated into dike systems that prevent saltwater flooding and allow upland drainage to the estuary during low tide. By preventing tidal exchange, tide gates have significant upstream effects on water temperature and chemistry, plant and animal community structure, and geomorphology. Since they are closed most of the day and may be difficult to pass when open, tide gates may act as fish passage barriers for juvenile salmonids. They may also affect juvenile salmon migration timing by altering environmental variables that influence emigration rate in upstream habitats. We conducted our research in Coos Bay, one of the many Oregon estuaries with extensive use of tide gates. We studied three streams, one with a top-hinged tide gate, one with a side-hinged gate, and one without any tide gates that acted as our reference site. Our study species was coho salmon, Oncorhynchus kisutch, which may encounter tide gates both in the subyearling and smolt life stages in our study streams. Our objectives were to: 1) quantify upstream and downstream fish passage occurrence at all three sites, 2) determine whether juvenile coho salmon passage is associated with a specific range of gate conditions, and 3) identify any associations between coho smolt emigration rate and environmental variables that are influenced by tide gates. We installed stationary passive integrated transponder (PIT) antennae around both tide gates and a tidal channel in the non-gated stream to record the movement of PIT tagged juvenile coho salmon. Coho salmon smolts passed upstream most frequently at the non-gated channel (48% of all smolts detected at the array), next the side-hinged gate (28%), and lastly, the top-hinged gate (3%). Juvenile coho salmon passed more frequently at a specific range of gate angles and tailwater depths at both top hinged and side-hinged tide gates. Smolts passed downstream more frequently at greater gate angles and tailwater depths than available on average at both tide gates. Subyearlings passed upstream more frequently during small gate angles and a narrow range of tailwater depths at the top-hinged gate but did not pass more frequently under a particular range of conditions at the side-hinged gate. At the top-hinged gate, conditions favorable for subyearling upstream passage occurred towards the end of the gate open period and therefore subyearlings were severely limited in their opportunities for passage. At multiple sites, emigration rate was associated with environmental variables that may be altered by tide gates. Increases in water temperature were associated with an increasing likelihood of smolt emigration at multiple sites. At a tide gate that allowed upstream estuarine influence, increasing salinity was associated with a decreasing likelihood of emigration. Our results suggest that tide gates may interfere with salmonid movement and migration by creating physical barriers to fish passage and potentially influencing migratory timing by altering environmental variables. When installing or retrofitting tide gates, these factors should be taken into consideration since a tide gate's design may determine the severity of its effects on salmonids. Our work should be considered a case study and the findings should not be assumed to be transferable due to the great diversity of tide gate installations in use. We recommend further research, including a more in depth analysis of the affects of tide gates on subyearling coho salmon and an investigation of piscivorous predator exploitation of tide gates. Close