Search

Search Results

• 1. [Article] Integration of oceanographic information off the Washington and Oregon coasts into west coast groundfish ecology and fisheries management

  To date, the use of oceanographic data in fisheries management has been limited by the scarcity and the difficulty of accessing complete oceanographic datasets. Consequently, fish stocks are managed with ...

  Citation × Citation Citation Abstract Copy Title: Integration of oceanographic information off the Washington and Oregon coasts into west coast groundfish ecology and fisheries management Author: Juan Jorda, Maria Jose To date, the use of oceanographic data in fisheries management has been limited by the scarcity and the difficulty of accessing complete oceanographic datasets. Consequently, fish stocks are managed with limited knowledge about the habitat where fish live and incomplete understanding of what oceanographic conditions affect their populations. With the long-term goal to improve science for ecosystem-based management of the West Coast groundfish fishery, this study had three objectives. First, the assembling and merging of disperse oceanographic datasets for temperature, salinity, chlorophyll-a and current velocity from the 1930s to the year 2004 off the Washington and Oregon coasts. Second, the generation of oceanographic data products relevant for fisheries research, consisting of the computation and the plotting of climatological monthly means, standard deviations and coefficients of variation for a variety of ocean variables at several depths. Third, the development of an exploratory example of how oceanographic information collected in this study can be of use to improve the science and management of groundfish. Thus, a study was developed to investigate if groundfish distribution and abundances are associated with any ocean habitat or individual oceanographic variables, using a combination of univariate, classification and ordination techniques. The fish data were derived from a routine bottom trawl survey conducted by the National Oceanic and Atmospheric Administration Northwest Fisheries Science Center (NOAA-NWFSC). Five ocean habitats with distinct physical and biological characteristics were identified off the Washington and Oregon coast: Offshore Habitat, Upwelling Habitat, Highly Variable Upwelling Habitat, River Plume Habitat, and Highly Variable Habitat. These ocean habitats were characteristic of cold-regime summer upwelling conditions. Overall, the analyses suggested that the species composition differ among the five ocean habitats. Some species were highly indicative of some habitats; however, overall the associations were weak due to the high degree of overlap of ocean habitats in terms of species composition. All the analyses were consistent in associating shallower species with the shallowest habitats (the Highly Variable, River Plume and Upwelling habitats) and the deeper species with the deeper habitats (the Offshore and the Highly Variable Upwelling habitats), suggesting that groundfish are adapted to wide environmental ranges. In addition, the overall abundance and diversity of groundfish was higher in the shallower habitats. In contrast, groundfish species showed strong associations with individual environmental factors, primarily depth, surface chlorophyll-a, and salinity and temperature at the bottom of the seafloor, indicating that groundfish distributions are mainly organized along depth gradients. Latitudinal variations in upwelling intensity, river discharge and productivity along the coast were also important factors influencing shallow species distributions and abundances. For example, three regions with high chlorophyll-a concentrations were associated with large abundances of specific groundfish species. These regions were found over Heceta Bank, over the Juan de Fuca canyon and in the Columbia River Plume. This study began with the assembly of several ocean variables and the development of some preliminary ocean data products relevant to fisheries studies. However, the addition of other ocean variables, such as dissolved oxygen, and the computation of new ocean products, such as mixed-layer depth, and thermocline depth and strength, would be valuable. Future work should involve more interdisplinary studies between fisheries and oceanography, the integration of oceanographic information off the west coast of the U.S., and the collection of concurrent ocean data at each fish trawl location. Title: Integration of oceanographic information off the Washington and Oregon coasts into west coast groundfish ecology and fisheries management Author: Juan Jorda, Maria Jose To date, the use of oceanographic data in fisheries management has been limited by the scarcity and the difficulty of accessing complete oceanographic datasets. Consequently, fish stocks are managed with limited knowledge about the habitat where fish live and incomplete understanding of what oceanographic conditions affect their populations. With the long-term goal to improve science for ecosystem-based management of the West Coast groundfish fishery, this study had three objectives. First, the assembling and merging of disperse oceanographic datasets for temperature, salinity, chlorophyll-a and current velocity from the 1930s to the year 2004 off the Washington and Oregon coasts. Second, the generation of oceanographic data products relevant for fisheries research, consisting of the computation and the plotting of climatological monthly means, standard deviations and coefficients of variation for a variety of ocean variables at several depths. Third, the development of an exploratory example of how oceanographic information collected in this study can be of use to improve the science and management of groundfish. Thus, a study was developed to investigate if groundfish distribution and abundances are associated with any ocean habitat or individual oceanographic variables, using a combination of univariate, classification and ordination techniques. The fish data were derived from a routine bottom trawl survey conducted by the National Oceanic and Atmospheric Administration Northwest Fisheries Science Center (NOAA-NWFSC). Five ocean habitats with distinct physical and biological characteristics were identified off the Washington and Oregon coast: Offshore Habitat, Upwelling Habitat, Highly Variable Upwelling Habitat, River Plume Habitat, and Highly Variable Habitat. These ocean habitats were characteristic of cold-regime summer upwelling conditions. Overall, the analyses suggested that the species composition differ among the five ocean habitats. Some species were highly indicative of some habitats; however, overall the associations were weak due to the high degree of overlap of ocean habitats in terms of species composition. All the analyses were consistent in associating shallower species with the shallowest habitats (the Highly Variable, River Plume and Upwelling habitats) and the deeper species with the deeper habitats (the Offshore and the Highly Variable Upwelling habitats), suggesting that groundfish are adapted to wide environmental ranges. In addition, the overall abundance and diversity of groundfish was higher in the shallower habitats. In contrast, groundfish species showed strong associations with individual environmental factors, primarily depth, surface chlorophyll-a, and salinity and temperature at the bottom of the seafloor, indicating that groundfish distributions are mainly organized along depth gradients. Latitudinal variations in upwelling intensity, river discharge and productivity along the coast were also important factors influencing shallow species distributions and abundances. For example, three regions with high chlorophyll-a concentrations were associated with large abundances of specific groundfish species. These regions were found over Heceta Bank, over the Juan de Fuca canyon and in the Columbia River Plume. This study began with the assembly of several ocean variables and the development of some preliminary ocean data products relevant to fisheries studies. However, the addition of other ocean variables, such as dissolved oxygen, and the computation of new ocean products, such as mixed-layer depth, and thermocline depth and strength, would be valuable. Future work should involve more interdisplinary studies between fisheries and oceanography, the integration of oceanographic information off the west coast of the U.S., and the collection of concurrent ocean data at each fish trawl location. Close

• 2. [Article] thesisFIGS.PPT

  Citation × Citation Citation Abstract Copy Title: thesisFIGS.PPT Author: Nasby, Nicole M. Title: thesisFIGS.PPT Author: Nasby, Nicole M. Close

• 3. [Article] Nasby_Thesis.doc

  Citation × Citation Citation Abstract Copy Title: Nasby_Thesis.doc Author: Nasby, Nicole M. Title: Nasby_Thesis.doc Author: Nasby, Nicole M. Close

• 4. [Article] Integration of submersible transect data and high-resolution sonar imagery for a habitat-based groundfish assessment of Heceta Bank, Oregon

  Citation × Citation Citation Abstract Copy Title: Integration of submersible transect data and high-resolution sonar imagery for a habitat-based groundfish assessment of Heceta Bank, Oregon Author: Nasby, Nicole M. Title: Integration of submersible transect data and high-resolution sonar imagery for a habitat-based groundfish assessment of Heceta Bank, Oregon Author: Nasby, Nicole M. Close

• 5. [Article] The Responses of Slope-spawning Flatfish to Environmental Variability in the Eastern Bering Sea

  When adult spawning and juvenile settling locations of marine fishes are geographically separated, their early life history stages must rely on transport and their own behavior to move them toward suitable ...

  Citation × Citation Citation Abstract Copy Title: The Responses of Slope-spawning Flatfish to Environmental Variability in the Eastern Bering Sea Author: Vestfals, Cathleen D. When adult spawning and juvenile settling locations of marine fishes are geographically separated, their early life history stages must rely on transport and their own behavior to move them toward suitable habitats for successful recruitment to the juvenile phase. Variations in climate may reduce the availability of spawning and juvenile nursery habitats and alter ocean circulation patterns, which can disrupt dispersal pathways and affect life cycle closure. This research focused on two commercially- and ecologically-important flatfish species in the eastern Bering Sea (EBS), Greenland halibut (Reinhardtius hippoglossoides) and Pacific halibut (Hippoglossus stenolepis), which may be especially sensitive to climate variability due to strong seasonally and ontogenetically variable distributions and extended pelagic larval phases. Data from fishery-dependent and fishery-independent sources were analyzed to determine the influence of environmental variability on adult habitat use, thus gaining a uniquely comprehensive range of seasonal and geographic coverage of each species' distribution. Transport along and across the Bering Slope was characterized from 23 years (1982 - 2004) of simulations from a Regional Ocean Modeling System (ROMS) ocean circulation model, with the expectation that changes in the strength and position of the Bering Slope Current (BSC) would affect recruitment, and that circulation features along and across the shelf edge would be strongly influenced by atmospheric forcing. To understand the physical mechanisms of larval delivery to shelf nursery areas, Greenland and Pacific halibut dispersal pathways were simulated from their source (e.g., spawning areas over the continental slope) to settlement locations (e.g., juvenile nursery areas on the continental shelf) using DisMELS (Dispersal Model for Early Life Stages), an individual-based particle-tracking model. Spatial patterns of dispersal were characterized for each species and for years with contrasting settlement success to understand the influence of local oceanographic and atmospheric conditions on dispersal corridor use. Adult Greenland and Pacific halibut exhibited strong and contrasting responses to changes in temperature on the shelf, with catches decreasing and increasing, respectively, at approximately 1°C. The effect of temperature was not as prominent along the slope, suggesting that slope habitats may provide some insulation from shelf-associated environmental variability, particularly for Greenland halibut. With warming, Greenland halibut exhibited more of a bathymetric shift in distribution, while the shift was more latitudinal for Pacific halibut. Habitat partitioning may, in part, explain differences in Greenland and Pacific halibut adult distributions. Analysis of modeled circulation revealed strong variations in the strength and position of the BSC, with changes in along-shelf and cross-shelf flow associated with changes in recruitment. Greenland halibut benefitted from decreased along-shelf and on-shelf flow, while Pacific halibut benefitted from on-shelf flows through Bering and Pribilof canyons. Variability in transport and the BSC position was strongly influenced by winds, ice cover, and large-scale climatic drivers. Greenland and Pacific halibut dispersal pathways varied between years, with distinct differences in dispersal characteristics found between the two species. In general, Greenland halibut connected to shelf nursery areas via more northern corridors, while Pacific halibut connected through more southern ones. In years with poor settlement success, the reverse pattern was observed. Greenland halibut dispersal metrics were strongly correlated with along- and cross-shelf transport, as well as NW along-shelf winds and ice, while Pacific halibut had strong associations with SW onshelf winds. Spawning time and location, along with climate-induced changes in circulation, appear to differentially affect Greenland and Pacific halibut dispersal pathways, which can lead to variations in their recruitment. Overall, Greenland and Pacific halibut had contrasting responses to similar environmental forcing, and predicted climate change is expected to impact these species in different ways. With increasing warming on the EBS shelf, they will likely further partition their habitats, with Greenland halibut finding colder refuges along the slope and Pacific halibut inhabiting larger portions of the shelf. Climate-induced changes in circulation were found to affect the transport of halibut eggs and larvae and their recruitment to the juvenile phase, which suggests an important role in their slope-shelf connectivity. Results of this study suggest that Greenland and Pacific halibut use different mechanisms to move from their spawning locations along the slope to their settlement areas on the shelf, and that environmental conditions that increase slope-shelf connectivity for one species will likely result in reduced connectivity for the other. This research improves our understanding of how slopespawning flatfish respond to a changing ocean environment, which is important for effective management of their populations, as predicted climate change will likely alter their habitat use and population dynamics. Title: The Responses of Slope-spawning Flatfish to Environmental Variability in the Eastern Bering Sea Author: Vestfals, Cathleen D. When adult spawning and juvenile settling locations of marine fishes are geographically separated, their early life history stages must rely on transport and their own behavior to move them toward suitable habitats for successful recruitment to the juvenile phase. Variations in climate may reduce the availability of spawning and juvenile nursery habitats and alter ocean circulation patterns, which can disrupt dispersal pathways and affect life cycle closure. This research focused on two commercially- and ecologically-important flatfish species in the eastern Bering Sea (EBS), Greenland halibut (Reinhardtius hippoglossoides) and Pacific halibut (Hippoglossus stenolepis), which may be especially sensitive to climate variability due to strong seasonally and ontogenetically variable distributions and extended pelagic larval phases. Data from fishery-dependent and fishery-independent sources were analyzed to determine the influence of environmental variability on adult habitat use, thus gaining a uniquely comprehensive range of seasonal and geographic coverage of each species' distribution. Transport along and across the Bering Slope was characterized from 23 years (1982 - 2004) of simulations from a Regional Ocean Modeling System (ROMS) ocean circulation model, with the expectation that changes in the strength and position of the Bering Slope Current (BSC) would affect recruitment, and that circulation features along and across the shelf edge would be strongly influenced by atmospheric forcing. To understand the physical mechanisms of larval delivery to shelf nursery areas, Greenland and Pacific halibut dispersal pathways were simulated from their source (e.g., spawning areas over the continental slope) to settlement locations (e.g., juvenile nursery areas on the continental shelf) using DisMELS (Dispersal Model for Early Life Stages), an individual-based particle-tracking model. Spatial patterns of dispersal were characterized for each species and for years with contrasting settlement success to understand the influence of local oceanographic and atmospheric conditions on dispersal corridor use. Adult Greenland and Pacific halibut exhibited strong and contrasting responses to changes in temperature on the shelf, with catches decreasing and increasing, respectively, at approximately 1°C. The effect of temperature was not as prominent along the slope, suggesting that slope habitats may provide some insulation from shelf-associated environmental variability, particularly for Greenland halibut. With warming, Greenland halibut exhibited more of a bathymetric shift in distribution, while the shift was more latitudinal for Pacific halibut. Habitat partitioning may, in part, explain differences in Greenland and Pacific halibut adult distributions. Analysis of modeled circulation revealed strong variations in the strength and position of the BSC, with changes in along-shelf and cross-shelf flow associated with changes in recruitment. Greenland halibut benefitted from decreased along-shelf and on-shelf flow, while Pacific halibut benefitted from on-shelf flows through Bering and Pribilof canyons. Variability in transport and the BSC position was strongly influenced by winds, ice cover, and large-scale climatic drivers. Greenland and Pacific halibut dispersal pathways varied between years, with distinct differences in dispersal characteristics found between the two species. In general, Greenland halibut connected to shelf nursery areas via more northern corridors, while Pacific halibut connected through more southern ones. In years with poor settlement success, the reverse pattern was observed. Greenland halibut dispersal metrics were strongly correlated with along- and cross-shelf transport, as well as NW along-shelf winds and ice, while Pacific halibut had strong associations with SW onshelf winds. Spawning time and location, along with climate-induced changes in circulation, appear to differentially affect Greenland and Pacific halibut dispersal pathways, which can lead to variations in their recruitment. Overall, Greenland and Pacific halibut had contrasting responses to similar environmental forcing, and predicted climate change is expected to impact these species in different ways. With increasing warming on the EBS shelf, they will likely further partition their habitats, with Greenland halibut finding colder refuges along the slope and Pacific halibut inhabiting larger portions of the shelf. Climate-induced changes in circulation were found to affect the transport of halibut eggs and larvae and their recruitment to the juvenile phase, which suggests an important role in their slope-shelf connectivity. Results of this study suggest that Greenland and Pacific halibut use different mechanisms to move from their spawning locations along the slope to their settlement areas on the shelf, and that environmental conditions that increase slope-shelf connectivity for one species will likely result in reduced connectivity for the other. This research improves our understanding of how slopespawning flatfish respond to a changing ocean environment, which is important for effective management of their populations, as predicted climate change will likely alter their habitat use and population dynamics. Close