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American Eel Dynamics ( Anguilla rostrata ) in Hudson River Tributaries, New York

American Eel Dynamics ( Anguilla rostrata ) in Hudson River Tributaries, New York. Leonard S. Machut 1 , Karin E. Limburg 1 , and Robert E. Schmidt 2 1 - SUNY College of Environmental Science & Forestry 2 – Simons Rock College. http://www.nanfa.org/akiweb/974.JPG. Goals/Research Questions.

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American Eel Dynamics ( Anguilla rostrata ) in Hudson River Tributaries, New York

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  1. American Eel Dynamics (Anguilla rostrata) in Hudson River Tributaries, New York Leonard S. Machut1, Karin E. Limburg1, and Robert E. Schmidt2 1 - SUNY College of Environmental Science & Forestry 2 – Simons Rock College http://www.nanfa.org/akiweb/974.JPG

  2. Goals/Research Questions • Extend results of previous studies into tributaries of the Hudson River • EelPopulation • Where are they? • What are their condition? • Nematode infection • Prevalence? • Intensity?

  3. Wynants Kill, 7 Barriers Hannacroix Creek 5 Barriers Saw Kill, 7 Barriers Black Creek 9 Barriers • Stratified random sampling for lab analysis • 232 of 1938 captured Peekskill Hollow 4 Barriers Minisceongo Creek 7 Barriers

  4. Barriers: An Important Role

  5. Barriers: An Important Role(cont’d.)

  6. Tributary Populations • Multiple Regression Ln(P) = 26.166 – 2.730*Ln(B) – 0.165*D + 1.359*U where: P = Population B = Number of Barriers D = Distance Group U = Subcatchment Urbanization • r2 = 0.65, p < 0.001

  7. Size Distribution Length of Hudson River mainstem eels

  8. Size matters! 8 4 2 1 355 594 317 215 202 35 22 131 22 12 15

  9. Eel Condition • Standardized residuals of eel wet weight • regressed against total length • Ex.) An eel of -1 is 1 S. D. lighter than average Percent Riparian Urbanization Determined by Gap Analysis BII = Barrier Intensity Index

  10. Impacts of Barrier Intensity • As barrier intensity increases, eels able to reach these habitats grow faster

  11. Nematode Infection • Anguillicola Crassus - swimbladder parasite • Morrison & Secor, 2003 – Hudson River • 1997 – prevalence less than 20% • 2000 – prevalence over 60% • Intensity rose from <4 to 3.2 - 23.7 nematodes/eel

  12. Tributary Invasion • 2003 & 04 Sampling • Range = 0-20 nematodes/eel • Prevalence (P) = 39.2% • Intensity (I) = 2.44 nematodes/infected eel Wynants Kill P = 51.9% I = 2.36 Hannacroix P = 35.7% I = 2.60 Black Creek P = 31.6% I = 2.25 Saw Kill P = 34.5% I = 1.70 Minisceonga P = 40.4% I = 2.57 Peekskill P = 43.6% I = 2.77 Morrison and Secor, 2003 Prevalence = 60% Intensity = 3.2-23.7 - http://www.dnr.cornell.edu/hydro2/hmap.gif

  13. Country Eels? • Not significant (p = 0.14) but an upward trend as urbanization increases • What does this mean?

  14. The Silver Lining… • Barriers are slowing nematode invasion

  15. Eel Condition • No significant difference

  16. In Summary • The first barrier appears to reduce eel densities by at least a factor of 10 • Increased urbanization negatively affects eel health • Infection with Anguillicola crassus is lower in tributaries than the Hudson mainstem • A. crassus invasion is ongoing – dams may slow infection rates in tributaries

  17. A special thanks to: Evan Leibu, Adlai Lang, Nsekan Smith, Jackie Andersen, Emilio Menvielle, Omar Gordon, Paul Simonin, Bob Daniels, and the Hudson River Foundation References available upon request @ lsmachut@syr.edu

  18. Questions? http://www.nanfa.org/akiweb/974.JPG

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