Search

Search Results

• 81. [Article] Factors Influencing the Survival of Outmigrating Juvenile Salmonids Through Multiple Dam Passages: An Individual-Based Approach

  Substantial declines of Pacific salmon populations have occurred over the past several decades related to large-scale anthropogenic and climatic changes in freshwater and marine environments. In the Columbia ...

  Citation × Citation Citation Abstract Copy Title: Factors Influencing the Survival of Outmigrating Juvenile Salmonids Through Multiple Dam Passages: An Individual-Based Approach Author: Elder, Timothy, Woodley, Christa M., Weiland, Mark A., Strecker, Angela L. Year: 2016 Substantial declines of Pacific salmon populations have occurred over the past several decades related to large-scale anthropogenic and climatic changes in freshwater and marine environments. In the Columbia River Basin, migrating juvenile salmonids may pass as many as eight large-scale hydropower projects before reaching the ocean; however, the cumulative effects of multiple dam passages are largely unknown. Using acoustic transmitters and an extensive system of hydrophone arrays in the Lower Columbia River, we calculated the survival of yearling Chinook salmon (Oncorhynchus tshawytscha) and steelhead (O. mykiss) passing one, two, or three dams. We applied a unique index of biological characteristics and environmental exposures, experienced by each fish individually as it migrated downstream, in order to examine which factors most influence salmonid survival. High outflow volumes led to involuntary spill in 2011 and created an environment of supersaturated dissolved gas concentrations. In this environment, migrating smolt survival was strongly influenced by barometric pressure, fish velocity, and water temperature. The effect of these variables on survival was compounded by multiple dam passages compared to fish passing a single dam. Despite spatial isolation between dams in the Lower Columbia River hydrosystem, migrating smolt appear to experience cumulative effects akin to a press disturbance. In general, Chinook salmon and steelhead respond similarly in terms of survival rates and responses to altered environmental conditions. Management actions that limit dissolved gas concentrations in years of high flow will benefit migrating salmonids at this life stage. Title: Factors Influencing the Survival of Outmigrating Juvenile Salmonids Through Multiple Dam Passages: An Individual-Based Approach Author: Elder, Timothy, Woodley, Christa M., Weiland, Mark A., Strecker, Angela L. Year: 2016 Substantial declines of Pacific salmon populations have occurred over the past several decades related to large-scale anthropogenic and climatic changes in freshwater and marine environments. In the Columbia River Basin, migrating juvenile salmonids may pass as many as eight large-scale hydropower projects before reaching the ocean; however, the cumulative effects of multiple dam passages are largely unknown. Using acoustic transmitters and an extensive system of hydrophone arrays in the Lower Columbia River, we calculated the survival of yearling Chinook salmon (Oncorhynchus tshawytscha) and steelhead (O. mykiss) passing one, two, or three dams. We applied a unique index of biological characteristics and environmental exposures, experienced by each fish individually as it migrated downstream, in order to examine which factors most influence salmonid survival. High outflow volumes led to involuntary spill in 2011 and created an environment of supersaturated dissolved gas concentrations. In this environment, migrating smolt survival was strongly influenced by barometric pressure, fish velocity, and water temperature. The effect of these variables on survival was compounded by multiple dam passages compared to fish passing a single dam. Despite spatial isolation between dams in the Lower Columbia River hydrosystem, migrating smolt appear to experience cumulative effects akin to a press disturbance. In general, Chinook salmon and steelhead respond similarly in terms of survival rates and responses to altered environmental conditions. Management actions that limit dissolved gas concentrations in years of high flow will benefit migrating salmonids at this life stage. Close

• 82. [Article] Coordinated Population Forecast for Grant County, its Urban Growth Boundaries (UGB), and Area Outside UGBs 2016-2066

  Grant County’s total population has declined since 2000, losing an average of about 50 persons per year between 2000 and 2010 (Figure 1). With the exception of minimal population increase among three small ...

  Citation × Citation Citation Abstract Copy Title: Coordinated Population Forecast for Grant County, its Urban Growth Boundaries (UGB), and Area Outside UGBs 2016-2066 Author: Portland State University. Population Research Center, Ruan, Xiaomin, Proehl, Risa, Jurjevich, Jason R., Rancik, Kevin, Kessi, Janai, Tetrick, David, Michel, Julia Year: 2016 Grant County’s total population has declined since 2000, losing an average of about 50 persons per year between 2000 and 2010 (Figure 1). With the exception of minimal population increase among three small UGBs, every sub-area recorded population loss during the 2000s. Prairie City and the area outside UGBs posted the largest losses, losing on average about 17 and 19 persons per year, respectively. Grant County’s population decline in the 2000s was the result of a consistent natural decrease as well as relatively steady net out-migration (Figure 12). The smaller number of births relative to deaths led to a natural decrease (more deaths than births) in nearly every year from 2000 to 2015. While net out-migration was common during the last decade (2000-2010), in recent years (2010-2015) net in-migration has occurred. Even so, natural decrease has persisted and generally exceeded net in-migration, leading to continued population decline. Grant County is expected to experience population decline over the 50-year forecast period. This population loss will likely occur at a relatively uniform rate among the county’s sub-areas, with losses occurring at an increasing rate as time progresses. For Grant County as a whole, increasing natural decrease and relatively steady net in-migration are expected to lead to population decline. An aging population is expected to not only lead to an increase in deaths, but a smaller proportion of women in their childbearing years will likely result in a long-term decline in births. Net in-migration is expected to persist throughout the entire forecast period, but will not fully offset the natural decrease, leading to population decline. Title: Coordinated Population Forecast for Grant County, its Urban Growth Boundaries (UGB), and Area Outside UGBs 2016-2066 Author: Portland State University. Population Research Center, Ruan, Xiaomin, Proehl, Risa, Jurjevich, Jason R., Rancik, Kevin, Kessi, Janai, Tetrick, David, Michel, Julia Year: 2016 Grant County’s total population has declined since 2000, losing an average of about 50 persons per year between 2000 and 2010 (Figure 1). With the exception of minimal population increase among three small UGBs, every sub-area recorded population loss during the 2000s. Prairie City and the area outside UGBs posted the largest losses, losing on average about 17 and 19 persons per year, respectively. Grant County’s population decline in the 2000s was the result of a consistent natural decrease as well as relatively steady net out-migration (Figure 12). The smaller number of births relative to deaths led to a natural decrease (more deaths than births) in nearly every year from 2000 to 2015. While net out-migration was common during the last decade (2000-2010), in recent years (2010-2015) net in-migration has occurred. Even so, natural decrease has persisted and generally exceeded net in-migration, leading to continued population decline. Grant County is expected to experience population decline over the 50-year forecast period. This population loss will likely occur at a relatively uniform rate among the county’s sub-areas, with losses occurring at an increasing rate as time progresses. For Grant County as a whole, increasing natural decrease and relatively steady net in-migration are expected to lead to population decline. An aging population is expected to not only lead to an increase in deaths, but a smaller proportion of women in their childbearing years will likely result in a long-term decline in births. Net in-migration is expected to persist throughout the entire forecast period, but will not fully offset the natural decrease, leading to population decline. Close

• 83. [Article] The economic incentives facing illegal Mexican aliens in the U.S. : a case study at Hood River, Oregon

  Illegal Mexican migration to the U.S. appears to have increased substantially over the past fifteen years. Most illegal Mexican aliens migrate with the aim of obtaining better employment opportunities ...

  Citation × Citation Citation Abstract Copy Title: The economic incentives facing illegal Mexican aliens in the U.S. : a case study at Hood River, Oregon Author: Cuthbert, Richard W. Illegal Mexican migration to the U.S. appears to have increased substantially over the past fifteen years. Most illegal Mexican aliens migrate with the aim of obtaining better employment opportunities and higher earnings in the U.S. than are available in Mexico. The potential impacts of this migration on various U.S. interests, however, are not agreed upon by scholars in the field. In fact, little empirical data on illegal Mexican aliens in the U.S. have been collected, especially with regard to the economic incentives for their migration. This study is an attempt to obtain empirical data on illegal Mexican aliens who are employed in the U.S. The principle aim of this research is to describe a random sample of illegal Mexican aliens surveyed at Hood River, Oregon, where they were employed in agricultural harvest activities. Specific attention is placed on the earnings differential for illegal Mexican aliens in the U.S. and foregone earnings in Mexico as a measure of the economic incentive for illegal migration. The study finds that illegal Mexican aliens interviewed at Hood River generally conform to the demographic profile described in previous studies. but that the data on their earnings and expenditures are considerably different. Both wage earnings and living costs in the U.S. appear to be considerably higher for most illegal Mexican aliens than indicated by previous studies, and their differential between potential U.S. and Mexican earnings is substantial. Illegal Mexican aliens at Hood River had gross earnings of approximately six-times their foregone Mexican earnings by working in the U.S. for roughly the same period of time. By accounting for expenses that the illegal aliens face in the U.S., this amount is reduced to four-times their foregone earnings. The study concludes that considerable illegal Mexican migration will likely continue in the near future and that further research on other aspects of the phenomenon and in other geographic regions would be useful. Several specific suggestions for future research are also outlined. Title: The economic incentives facing illegal Mexican aliens in the U.S. : a case study at Hood River, Oregon Author: Cuthbert, Richard W. Illegal Mexican migration to the U.S. appears to have increased substantially over the past fifteen years. Most illegal Mexican aliens migrate with the aim of obtaining better employment opportunities and higher earnings in the U.S. than are available in Mexico. The potential impacts of this migration on various U.S. interests, however, are not agreed upon by scholars in the field. In fact, little empirical data on illegal Mexican aliens in the U.S. have been collected, especially with regard to the economic incentives for their migration. This study is an attempt to obtain empirical data on illegal Mexican aliens who are employed in the U.S. The principle aim of this research is to describe a random sample of illegal Mexican aliens surveyed at Hood River, Oregon, where they were employed in agricultural harvest activities. Specific attention is placed on the earnings differential for illegal Mexican aliens in the U.S. and foregone earnings in Mexico as a measure of the economic incentive for illegal migration. The study finds that illegal Mexican aliens interviewed at Hood River generally conform to the demographic profile described in previous studies. but that the data on their earnings and expenditures are considerably different. Both wage earnings and living costs in the U.S. appear to be considerably higher for most illegal Mexican aliens than indicated by previous studies, and their differential between potential U.S. and Mexican earnings is substantial. Illegal Mexican aliens at Hood River had gross earnings of approximately six-times their foregone Mexican earnings by working in the U.S. for roughly the same period of time. By accounting for expenses that the illegal aliens face in the U.S., this amount is reduced to four-times their foregone earnings. The study concludes that considerable illegal Mexican migration will likely continue in the near future and that further research on other aspects of the phenomenon and in other geographic regions would be useful. Several specific suggestions for future research are also outlined. Close

• 84. [Article] Bioenergetic evaluation of diel vertical migration by bull trout

  I evaluated hypotheses related to growth as a driver of depth use and diel vertical migration by bull trout (Salvelinus confluentus) in a thermally stratified reservoir. I applied a bioenergetic model ...

  Citation × Citation Citation Abstract Copy Title: Bioenergetic evaluation of diel vertical migration by bull trout Author: Eckmann, Madeleine I evaluated hypotheses related to growth as a driver of depth use and diel vertical migration by bull trout (Salvelinus confluentus) in a thermally stratified reservoir. I applied a bioenergetic model to evaluate growth of bull trout in relation to potential patterns of diel depth use by bull trout in Ross Lake, Washington. Modeled patterns of growth were derived from observed vertical distributions of temperature and prey availability. I also observed bull trout depth (and corresponding temperature) use patterns to determine if observed behaviors corresponded with those predicted to maximize growth. Results of this work suggest that bull trout migrations beyond 25 m deep in Ross Lake cannot be explained exclusively by growth and survival alone, two common explanations for diel vertical migration. These deeper excursions may be explained by a third driver that has not been previously emphasized: the importance of colder water for gametogenesis. Further evaluation of this hypothesis as a means of explaining diel vertical migration for bull trout and other fish species in similar environments is warranted. Title: Bioenergetic evaluation of diel vertical migration by bull trout Author: Eckmann, Madeleine I evaluated hypotheses related to growth as a driver of depth use and diel vertical migration by bull trout (Salvelinus confluentus) in a thermally stratified reservoir. I applied a bioenergetic model to evaluate growth of bull trout in relation to potential patterns of diel depth use by bull trout in Ross Lake, Washington. Modeled patterns of growth were derived from observed vertical distributions of temperature and prey availability. I also observed bull trout depth (and corresponding temperature) use patterns to determine if observed behaviors corresponded with those predicted to maximize growth. Results of this work suggest that bull trout migrations beyond 25 m deep in Ross Lake cannot be explained exclusively by growth and survival alone, two common explanations for diel vertical migration. These deeper excursions may be explained by a third driver that has not been previously emphasized: the importance of colder water for gametogenesis. Further evaluation of this hypothesis as a means of explaining diel vertical migration for bull trout and other fish species in similar environments is warranted. Close

• 85. [Article] Factors influencing spawning migration of bull trout (Salvelinus confluentus) in the North Fork Skokomish River, Olympic National Park, Washington

  Distribution and life history characteristics of lacustrine-adfluvial bull trout (Salvelinus confluentus) were described in the North Fork Skokomish River Basin (including Lake Cushman, a reservoir) from ...

  Citation × Citation Citation Abstract Copy Title: Factors influencing spawning migration of bull trout (Salvelinus confluentus) in the North Fork Skokomish River, Olympic National Park, Washington Author: Brenkman, Samuel J. Distribution and life history characteristics of lacustrine-adfluvial bull trout (Salvelinus confluentus) were described in the North Fork Skokomish River Basin (including Lake Cushman, a reservoir) from 1994 to 1996. Day snorkeling was conducted in the river to determine initiation of the bull trout spawning migration, abundance of spawners, and duration of spawning. Declining photoperiod, increased river discharge, and decreased water temperature appeared to influence timing of migration and spawning. Lacustrine-adfluvial bull trout typically entered the North Fork Skokomish River in October although some fish entered as early as May. Mean lengths of spawners consistently increased from June to December 1996, and early migrating bull trout were shorter than those fish that entered after river discharge increased in October. The presence of two phases of the spawning migration may be indicative of two populations spawning in the river. Bull trout spawned between mid-September and December in the river and tributaries after water temperatures declined. All spawning occurred at temperatures less than 7.5°C. Comparisons with studies of other lacustrine-adfiuvial bull trout populations that inhabit river and reservoir complexes suggested that bull trout exhibit specific migratory strategies related to local environmental conditions. In the North Fork Skokomish River, changes in abundance of bull trout, mountain whitefish (Prosopium wilhamsom), cutthroat trout (Oncorhynchus dark), and rainbow trout (Oncorhynchus mykiss) revealed distinct temporal segregation among these species. Olympic National Park, a designated Biosphere Reserve, contains one of the largest remaining areas of relatively pristine habitat in the range of bull trout. Knowledge of responses of bull trout to changes in river discharge and temperature from relatively undisturbed systems, such as the North Fork Skokomish River, may be useful in understanding patterns observed in degraded environments. Title: Factors influencing spawning migration of bull trout (Salvelinus confluentus) in the North Fork Skokomish River, Olympic National Park, Washington Author: Brenkman, Samuel J. Distribution and life history characteristics of lacustrine-adfluvial bull trout (Salvelinus confluentus) were described in the North Fork Skokomish River Basin (including Lake Cushman, a reservoir) from 1994 to 1996. Day snorkeling was conducted in the river to determine initiation of the bull trout spawning migration, abundance of spawners, and duration of spawning. Declining photoperiod, increased river discharge, and decreased water temperature appeared to influence timing of migration and spawning. Lacustrine-adfluvial bull trout typically entered the North Fork Skokomish River in October although some fish entered as early as May. Mean lengths of spawners consistently increased from June to December 1996, and early migrating bull trout were shorter than those fish that entered after river discharge increased in October. The presence of two phases of the spawning migration may be indicative of two populations spawning in the river. Bull trout spawned between mid-September and December in the river and tributaries after water temperatures declined. All spawning occurred at temperatures less than 7.5°C. Comparisons with studies of other lacustrine-adfiuvial bull trout populations that inhabit river and reservoir complexes suggested that bull trout exhibit specific migratory strategies related to local environmental conditions. In the North Fork Skokomish River, changes in abundance of bull trout, mountain whitefish (Prosopium wilhamsom), cutthroat trout (Oncorhynchus dark), and rainbow trout (Oncorhynchus mykiss) revealed distinct temporal segregation among these species. Olympic National Park, a designated Biosphere Reserve, contains one of the largest remaining areas of relatively pristine habitat in the range of bull trout. Knowledge of responses of bull trout to changes in river discharge and temperature from relatively undisturbed systems, such as the North Fork Skokomish River, may be useful in understanding patterns observed in degraded environments. Close

• 86. [Article] The influence of sex, migration distance, and latitude on expression of anadromy in Oncorhynchus mykiss

  The evolution and maintenance of multiple phenotypes within populations is an interesting evolutionary and ecological question, and is becoming increasingly important for the restoration and conservation ...

  Citation × Citation Citation Abstract Copy Title: The influence of sex, migration distance, and latitude on expression of anadromy in Oncorhynchus mykiss Author: Ohms, Haley The evolution and maintenance of multiple phenotypes within populations is an interesting evolutionary and ecological question, and is becoming increasingly important for the restoration and conservation of partially migratory species. In particular, why individuals adopt a particular phenotype has been the focus of numerous research efforts. In the partially migratory species Oncorhynchys mykiss (commonly known as steelhead and rainbow trout), I found that sex plays a strong role in whether an individual adopts an anadromous or resident life history. I observed a higher frequency of females adopting the anadromous tactic throughout the species range, and I attributed this to the relationship between body size and reproductive success in females that is not present in males. I did not observe differences in female bias along gradients of latitude or migration distance, and I hypothesize that while the frequency of tactics among populations may change along these gradients, either the change is equal between males and females, or an interaction of latitude and migration distance may control changes. I did not observe a corresponding male bias in the one resident population I sampled, and suggest that this is the result of a high frequency of residents in that population. I propose that sex ratios could be a valuable metric for measuring frequency of life-history tactics in populations and could facilitate the investigation into the controls of life-history tactics across broad scales. Title: The influence of sex, migration distance, and latitude on expression of anadromy in Oncorhynchus mykiss Author: Ohms, Haley The evolution and maintenance of multiple phenotypes within populations is an interesting evolutionary and ecological question, and is becoming increasingly important for the restoration and conservation of partially migratory species. In particular, why individuals adopt a particular phenotype has been the focus of numerous research efforts. In the partially migratory species Oncorhynchys mykiss (commonly known as steelhead and rainbow trout), I found that sex plays a strong role in whether an individual adopts an anadromous or resident life history. I observed a higher frequency of females adopting the anadromous tactic throughout the species range, and I attributed this to the relationship between body size and reproductive success in females that is not present in males. I did not observe differences in female bias along gradients of latitude or migration distance, and I hypothesize that while the frequency of tactics among populations may change along these gradients, either the change is equal between males and females, or an interaction of latitude and migration distance may control changes. I did not observe a corresponding male bias in the one resident population I sampled, and suggest that this is the result of a high frequency of residents in that population. I propose that sex ratios could be a valuable metric for measuring frequency of life-history tactics in populations and could facilitate the investigation into the controls of life-history tactics across broad scales. Close

• 87. [Article] Transhumance as an adaptive strategy of West Coast RV retirees

  This ethnography describes RV [recreational vehicle] seasonal migration as an adaptive, transhumant strategy. The study population is retired, transhumant migrants, who are members of a nation-wide, membership ...

  Citation × Citation Citation Abstract Copy Title: Transhumance as an adaptive strategy of West Coast RV retirees Author: Williams, Diane This ethnography describes RV [recreational vehicle] seasonal migration as an adaptive, transhumant strategy. The study population is retired, transhumant migrants, who are members of a nation-wide, membership camping organization. Fieldwork was conducted over a period of seven months at two sites located on the West Coast. These sites reflect northern and southern locations corresponding to seasonal migration patterns. Standard scholarly orientations to the study of retired RV seasonal migrants manifest ethnocentrism and a tendency to stereotype RVers as amenity-migrants. An original and primary objective of the present study was to reach beyond these conceptualizations and popularized images through first-hand, descriptive accounts collected within the context of the culture. This research expands on two existing studies focusing on social and cultural aspects of RV seasonal migration. In contrast to these accounts, the present study provides cultural description of the daily life of retired RVers focusing on the distinctive ways that members of this subculture express mainstream American cultural values underlying their adaptive strategies. This study proposes an alternative conceptualization of RV seasonal migration, derived from the culture itself. The conclusion is that these adaptive strategies reflect patterns of social organization, patterns of resource management, and patterns of social, familial, and interpersonal relationships, that are congruent with mainstream American cultural values of self-reliant individualism, equality, and material comfort; values that have historical, philosophical roots in the Protestant Work Ethic. The RVers' identity derives from maintaining membership in a temporary, fluid, mobile community. They have cohesive social networks with well-defined boundaries, which they defend against threats to group identity. This study contributes to an understanding of what RV seasonal migration means to the participants themselves, and by extension, to their families, to communities, and to our aging society. Title: Transhumance as an adaptive strategy of West Coast RV retirees Author: Williams, Diane This ethnography describes RV [recreational vehicle] seasonal migration as an adaptive, transhumant strategy. The study population is retired, transhumant migrants, who are members of a nation-wide, membership camping organization. Fieldwork was conducted over a period of seven months at two sites located on the West Coast. These sites reflect northern and southern locations corresponding to seasonal migration patterns. Standard scholarly orientations to the study of retired RV seasonal migrants manifest ethnocentrism and a tendency to stereotype RVers as amenity-migrants. An original and primary objective of the present study was to reach beyond these conceptualizations and popularized images through first-hand, descriptive accounts collected within the context of the culture. This research expands on two existing studies focusing on social and cultural aspects of RV seasonal migration. In contrast to these accounts, the present study provides cultural description of the daily life of retired RVers focusing on the distinctive ways that members of this subculture express mainstream American cultural values underlying their adaptive strategies. This study proposes an alternative conceptualization of RV seasonal migration, derived from the culture itself. The conclusion is that these adaptive strategies reflect patterns of social organization, patterns of resource management, and patterns of social, familial, and interpersonal relationships, that are congruent with mainstream American cultural values of self-reliant individualism, equality, and material comfort; values that have historical, philosophical roots in the Protestant Work Ethic. The RVers' identity derives from maintaining membership in a temporary, fluid, mobile community. They have cohesive social networks with well-defined boundaries, which they defend against threats to group identity. This study contributes to an understanding of what RV seasonal migration means to the participants themselves, and by extension, to their families, to communities, and to our aging society. Close

• 88. [Article] Housing Prices and Inter-urban Migration

  This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/regional-science...

  Citation × Citation Citation Abstract Copy Title: Housing Prices and Inter-urban Migration Author: Plantinga, Andrew J., Detang-Dessendre, Cécile, Hunt, Gary L., Piguet, Virginie This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/regional-science-and-urban-economics/. Title: Housing Prices and Inter-urban Migration Author: Plantinga, Andrew J., Detang-Dessendre, Cécile, Hunt, Gary L., Piguet, Virginie This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/regional-science-and-urban-economics/. Close

• 89. [Article] Utilization of the Columbia River Estuary by American shad, Alosa sapidissima (Wilson)

  The migrations, distribution, and feeding of American shad, Alosa sapidissima (Wilson), were studied from February 1980 through January 1981 in the Columbia River Estuary, an important rearing zone for young-of-the-year ...

  Citation × Citation Citation Abstract Copy Title: Utilization of the Columbia River Estuary by American shad, Alosa sapidissima (Wilson) Author: Hammann, Mark Gregory The migrations, distribution, and feeding of American shad, Alosa sapidissima (Wilson), were studied from February 1980 through January 1981 in the Columbia River Estuary, an important rearing zone for young-of-the-year shad. Sampling was performed with purse seine, beach seine, and otter trawl. Adult shad and large numbers of juveniles from the 1979 spawning (age group I) entered the estuary from the ocean in May 1980. Adults continued on their upstream migration while age group I juveniles appeared to congregate in the estuary, joining those (age group I) that had over-wintered there. Many young-of-the-year shad (age group 0) reached the estuary on their seaward migration in September 1980, during which time most of the age group I juveniles migrated back to the ocean. By January 1981, large numbers of young-of-the-year shad migrated to the ocean, although a few remained in the estuary. The stomachs of 26 adult shad and 503 juveniles were analyzed. Adults did not appear to feed during their upstream migration, but juvenile shad fed extensively. Diet varied with season, gear type, and salinity zone. Calanoid copepods were important throughout the year, but Corophium salmonis and Neomysis mercedis were important during fall, winter, and spring. Freshwater prey were consumed during summer and fall. The most important of these were Daphnia spp., Chironomidae larvae and pupae, and Trichoptera adults for shad feeding in shallow water near beaches. Title: Utilization of the Columbia River Estuary by American shad, Alosa sapidissima (Wilson) Author: Hammann, Mark Gregory The migrations, distribution, and feeding of American shad, Alosa sapidissima (Wilson), were studied from February 1980 through January 1981 in the Columbia River Estuary, an important rearing zone for young-of-the-year shad. Sampling was performed with purse seine, beach seine, and otter trawl. Adult shad and large numbers of juveniles from the 1979 spawning (age group I) entered the estuary from the ocean in May 1980. Adults continued on their upstream migration while age group I juveniles appeared to congregate in the estuary, joining those (age group I) that had over-wintered there. Many young-of-the-year shad (age group 0) reached the estuary on their seaward migration in September 1980, during which time most of the age group I juveniles migrated back to the ocean. By January 1981, large numbers of young-of-the-year shad migrated to the ocean, although a few remained in the estuary. The stomachs of 26 adult shad and 503 juveniles were analyzed. Adults did not appear to feed during their upstream migration, but juvenile shad fed extensively. Diet varied with season, gear type, and salinity zone. Calanoid copepods were important throughout the year, but Corophium salmonis and Neomysis mercedis were important during fall, winter, and spring. Freshwater prey were consumed during summer and fall. The most important of these were Daphnia spp., Chironomidae larvae and pupae, and Trichoptera adults for shad feeding in shallow water near beaches. Close

• 90. [Article] Cooperative Management of Trans-Boundary Fish Stocks: Implications for Tropical Tuna Management in the Pacific Island Region

  Suggested Bibliographic Reference: NAAFE Forum 2017 Proceedings, March 22-24, 2017. Compiled by Ann L. Shriver with assistance from Stefani Evers. North American Association of Fisheries Economists (NAAFE), ...

  Citation × Citation Citation Abstract Copy Title: Cooperative Management of Trans-Boundary Fish Stocks: Implications for Tropical Tuna Management in the Pacific Island Region Author: Tokunaga, Kanae Suggested Bibliographic Reference: NAAFE Forum 2017 Proceedings, March 22-24, 2017. Compiled by Ann L. Shriver with assistance from Stefani Evers. North American Association of Fisheries Economists (NAAFE), Corvallis, 2017. Title: Cooperative Management of Trans-Boundary Fish Stocks: Implications for Tropical Tuna Management in the Pacific Island Region Author: Tokunaga, Kanae Suggested Bibliographic Reference: NAAFE Forum 2017 Proceedings, March 22-24, 2017. Compiled by Ann L. Shriver with assistance from Stefani Evers. North American Association of Fisheries Economists (NAAFE), Corvallis, 2017. Close