Ocean Ecology

One of the key information gaps to be addressed by the NWFSC Ocean Ecology Team is how physical and biological processes in the estuary and ocean affect the distribution, growth, and survival of juvenile salmon and other fishes. Since we began our work in the late 1990s, salmon originating from rivers in the Pacific Northwest have undergone dramatic fluctuations in ocean survival. Juvenile salmon in the Columbia River estuary and coastal ocean may or may not be limited by estuarine and ocean habitat availability, food availability, predation, pathogens and parasites. We are presently conducting studies on the interactions among salmon, their biophysical habitat, food availability, and predation in estuarine and marine ecosystems. We are also contributing new information on the food web structure and ecosystem function in the Columbia River estuary, Columbia River plume, and coastal environments of Washington and Oregon.

Early life history studies

Under the direction of Drs. Richard Brodeur and Robert Emmett, FE scientists and their collaborators have examined ichthyoplankton samples from fixed stations off the Columbia River and Newport to investigate seasonal and interannual variability in fish recruitment. These data have been added to an existing database to examine long-term trends in ichthyoplankton abundance. From the 1970s to present, we have found major changes in the ichthyoplankton composition related to shifts in ocean conditions. In particular, sardines, anchovies, and jack mackerels have been spawning regularly off the Oregon Coast in contrast to some earlier periods. The timing of spawning of some species (e.g. anchovies) appears to be somewhat earlier than previously recorded. In 2004, a new program was initiated to examine seasonal variation in abundances of pre-recruit fishes, including rockfish. This project was funded by NOAA’s Stock Assessment Improvement Program and will examine fishery independent catch rates as an indication of relative success or failure of commercially important fish species off the Oregon Coast. Cruises are conducted monthly during summer/fall off Newport, Heceta Head, and the Columbia River. These surveys have found high numbers of juvenile rockfishes, but also found many larval and early juvenile hake, a species not regularly known to spawn off Oregon. Studies are presently underway to examine trophic interactions and growth of these juveniles and their role in the ecosystem off Oregon.

Ocean feeding ecology

Example of what the Columbia River plume front looks like. At certain phases of the tide, the boundary between the river and ocean water is visible as a long foam line between brownish water from the river and more grayish or bluish water from the ocean. All juvenile salmon exiting the Columbia River must pass through this boundary to enter the ocean. FE scientists study the interactions and ecological linkages within and between the California Current and Columbia River plume to investigate the effects of the plume and ocean conditions on growth and survival of juvenile salmonids. This project includes study of salmon feeding and relationships between feeding preferences and prey, and of the potential impact of salmonid fish predators on salmon survival. We have examined diets of salmon spanning multiple spatial and temporal scales and linked the variability in these diets to the environment and ultimate salmon survival. FE scientists also study interrelationships between salmon and sardines, anchovy, and herring. In conducting these studies, scientists use an ecosystem-based approach to investigate the biotic and abiotic factors that control growth, distribution, health and survival of important fish species and on the processes driving population fluctuations. For example, we are studying the effects of large populations of gelatinous zooplankton in coastal waters that may compete with salmon and other pelagic fish species. A steady-state ecosystem model has been developed as a tool for understanding the effects of changing fish stocks on ecosystem structure. Ultimately, this ecosystem-based research will be applied to management of fish stocks of the northern California Current.

Parasitology

Dr. Kym Jacobson and collaborators study parasites as fish pathogens and as indicators of ecosystem processes. One area of their research evaluates the potential contribution of salmon pathogens (bacteria and macroparasites) to growth and survival of juvenile salmon populations in the estuarine and ocean environments. Additional areas of research include using macroparasites to study food web structure of pelagic nekton, and to better understand migration and habitat use of pelagic fishes (with an emphasis on Pacific sardines, Sardinops sagax). These parasitology studies provide information on not only the fish host populations but also the dynamic coastal ecosystems.

Top predator studies

This component of our program is led by Dr. Jen Zamon. Her research approach uses predator-prey interactions to understand how potential salmon predators interact with salmon and other components of the coastal food web. She and her collaborators use marine bird and mammal distributions and behavior to determine what habitat types attract large numbers of predators. Common murres (Uria aalge) next to the plume front. These black-and-white seabirds are often found in large numbers at the front. Although they are only about the size of a football, they can dive up to 150 m in search of fish, krill, or other prey. Those habitats are then compared to surrounding habitat to understand what processes create predator aggregations. Predator distributions can be used to identify places and times when salmon or other fish might be vulnerable to predation, as well as to identify "ecological hot spots", areas of the ocean where energy passes rapidly through one or more links of the food web. Food web research is very useful for placing salmon or other organisms of interest in a functional ecosystem context. Such a context allows one to anticipate not only the direct effects of ecosystem change on salmon, but also the indirect effects of those changes. Dr. Zamon’s team is presently investigating the role a physical habitat feature (the Columbia River plume) plays in creating aggregations of fish-eating predators in the same location where juvenile salmon exit the Columbia River to begin life at sea. The research team uses a number of different but complementary methods to understand predator behavior, including mobile surveys on oceanographic research vessels, fixed surveys from land, satellite tracking of tagged individual predators, and diet analysis. Example of a seabird aggregation at the Columbia River plume front. The largest red and blue peaks (in the center of the graph) indicate the highest numbers of birds counted along a 27 kilometer transect. Greatest predator numbers occur at the plume front, the area where salinity (white line) changes abruptly from about 15 to 30. The plume front is the boundary between two water types: the ocean and the Columbia River.

New methods of pelagic fish assessment

Drs. Rick Brodeur and Jen Zamon are involved in a multidisciplinary study of the distribution of pelagic fishes off Oregon and Washington. The ultimate goal of this project is to substantially improve our understanding of the relationship between ecologically important key fish species (e.g. sardine, anchovy and albacore) and the physical environment by collecting synoptic measurements with improved spatial and temporal resolution of observations. Our partnership program is striving to develop a new method for detection of fish and synoptically mapping their environment at nested spatial and temporal scales. Photo of sardine schools (dark patches) around a commercial purse seine fishing vessel from the NOAA Twin Otter during LIDAR aerial surveys. This new technique involves employing aerial data collection techniques (which are able to collect data at a much larger range of temporal and spatial scales than traditional methods) and coupling them with directed and coordinated ship-based observations, buoy data, and satellite-derived information. Our aerial methodology employs the use of a state-of-the-art LIDAR system that uses lasers to analyze the distribution (vertical and horizontal) and size of fish schools in the upper water column while moving at a relatively high speed. Some technical details about the LIDAR system can be found at: (http://www.etl.noaa.gov/technology/instruments/floe/instrument.html). This nested array of observations are being analyzed and modeled in a GIS-based environment to provide qualitative and quantitative views of habitat- and behavioral-induced fish distribution patterns.

LIDAR echogram showing 6 individual fish targets at depths from 2—8 m over a distance of about 500 m along the flight track taken during August 2005.

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last modified 03/28/2007