American Eel Dynamics (Anguilla rostrata) in Hudson River Tributaries, New York Leonard S. Machut 1, Karin E. Limburg 1, and Robert E. Schmidt SUNY College of Environmental Science & Forestry 2 – Simons Rock College

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

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

Table 1: Watershed Characteristics for Censused Hudson River Tributaries Tributary Name WatershedStreamEelNumber ofDistance to% Artificial Area (km 2 )Length (km)Penetration (km) a Barriers1st Barrier (m)Barrier Wynants Kill Hannacroix Creek Saw Kill Black Creek Peekskill Hollow Minisceongo Creek a - Approximate distance upstream at which no eels were collected. We take this as an index of the degree to which eels penetrate and occupy a particular tributary.

Barriers: An Important Role

Barriers: An Important Role (cont’d.)

Tributary Populations Multiple Regression Ln(P) = – 2.730*Ln(B) – 0.165*D *U where: P = Population B = Number of Barriers D = Distance Group U = Subcatchment Urbanization –r 2 = 0.65, p < 0.001

Size Distribution Length of Hudson River mainstem eels

Size matters!

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

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

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 nematodes/eel

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 = Hannacroix P = 35.7% I = 2.60 Saw Kill P = 34.5% I = 1.70 Black Creek P = 31.6% I = 2.25 Minisceonga P = 40.4% I = 2.57 Peekskill P = 43.6% I = 2.77 Morrison and Secor, 2003 Prevalence = 60% Intensity =

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

The Silver Lining… Barriers are slowing nematode invasion Barriers are slowing nematode invasion

Eel Condition No significant difference

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

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

Questions?