20-3. Disentangling the complex interplay between life history characteristics and landscape and climatic stressors of commercially and culturally important fish species

CLOSED

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A distinct challenge in management of key fish species across large geographical extents is a limited understanding of the interplay between life history characteristics and changing landscape and climatic stressors.  A clear example of this is the limited understanding of the American eel, a commercially and culturally important fish species. The American eel (Anquilla rostrata) is a catadromous fish species native to eastern North America and the Caribbean and is of management interest to the US Fish and Wildlife Service (USFWS), the Atlantic States Marine Fisheries Commission (ASMFC), and multiple U.S. States.  American eel are long-lived and they have a complex life history as they spawn in the Atlantic Ocean (Sargasso Sea), are carried by ocean currents as larvae into coastal waters and estuaries, migrate up coastal rivers and streams as juveniles (elvers), mature as yellow eels, and ultimately out-migrate as silver eels to the Sargasso Sea to breed after which they die. Much remains unknown about this process and spawning has never been witnessed in the wild.  American eels once comprised up to a quarter of the biomass of fish species in Atlantic Coastal streams and were an important food source for American Indians and European settlers. Although not currently listed as endangered or threatened by USFWS, the populations are thought to be depleted due to restrictions on inland habitat access by dam building, habitat degradation, pollution, introduced parasites, and commercial harvest.  The status of the American eel fish stock is currently under assessment by the ASMFC and the species is ranked as one of the top Species of Greatest Conservation Need by multiple State Wildlife Action Plans. 

The USGS Eastern Ecological Science Center is continuing a successful history of research in support the ASMFC by building GIS-based habitat models to support American eel stock assessment activities.  Although there are data sets on American eel distribution and occurrence dating back over 100 years, there are many remaining scientific unknowns regarding life history characteristics, which limits assessments of the population status, particularly for the inland portion of the American eel range. These unknowns are driven by difficulty sampling for various life stages, little studied local habitat associations, and the broad geographic range that encompasses multiple habitat and climatic regimes. The sampling limitations are particularly acute for silver stage (out-migrating) eels, which cannot be legally harvested except in limited circumstances. Potential impacts from climate changes on American eel, including changing stream flow regimes (timing, flow frequency, and flow magnitude), increasing stream temperatures, and changes in ocean circulation patterns are almost completely unaddressed.  Particularly lacking is information on the interaction of changes in seasonal weather patterns and climatic conditions and triggering cues for key American eel life stages (e.g. silver eel outmigration).  Additionally, American eel populations are impacted by an invasive nematode worm (Anguillicoloides crassus), which affects the swim bladder, and these additional stressors may interact with climate change impacts to reduce population viability.  Without additional information, it is difficult to accurately design management regimes for protection and restoration of this culturally and commercially important species. Additionally, the lead PIs on this proposal are developing a regional approach to fish habitat assessments in the Chesapeake Bay watershed to augment the National Fish Habitat Partnership with finer scale and more management relevant analyses that will both inform and be informed by this research. 

There are multiple opportunities for a recent PhD graduate to conduct independent research within the overall goals of American eel and fisheries research projects of the EESC.  Many questions relevant to understanding life history characteristics of American eel remain unresolved, and there are information needs that are acutely relevant to assessment and management of the species from the perspective of the ASMFC and other agencies (e.g. USFWS).  For instance, the population status of the inland portion of the species range in the eastern U.S. is not well understood.  While the habitat access restrictions due to dams on in-migrating eels is broadly appreciated, the amount (length, area, volume) of potential habitat available but not currently used behind impassible barriers has not been quantified to date.  Likewise, the passability of barriers to out-migrating silver eels, and the temporal cues (water temperature, lunar phase) that trigger outmigration are not well understood.  Several temporal datasets exist that may inform this topic, including yearly monitoring of eel weirs in the Delaware River, and EESC research on fish passage structures. Additionally, the EESC has developed a rich spatial dataset on eel occurrence records and riverine and watershed habitat characteristics in the Chesapeake Bay and Delaware Bay watersheds, as well as other areas in the northeast U.S that would be applicable to these questions.  Any of these topics, as well as others related to climate change impacts, interactions with Anguillicoloides crassus, ecological flow needs, and local habitat characteristics would provide critical information to managers as well as to provide data, information, and models that would be of substantial impact to the wider scientific community. While these topics are specific to American eel, the ultimate goal is to build research frameworks applicable to information needs of multiple fish species. 

Interested applicants are strongly encouraged to contact the Research Advisor(s) early in the application process to discuss project ideas.

Proposed Duty Station: Leetown, West Virginia

Areas of PhD: Biology, ecology, environmental science, or related fields (candidates holding a Ph.D. in other disciplines, but with extensive knowledge and skills relevant to the Research Opportunity may be considered).

Qualifications:  Applicants must meet the qualifications for:  Research Biologist

(This type of research is performed by those who have backgrounds for the occupations stated above.  However, other titles may be applicable depending on the applicant's background, education, and research proposal. The final classification of the position will be made by the Human Resources specialist.)

Human Resources Office Contact:  Audrey Tsujita, 916-278-9395, atsujita@usgs.gov