# Presentation: 683498

## 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

## Goals/Research Questions

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

## Stratified random sampling for lab analysis

***Wynants Kill, ***
***7 Barriers***

***Saw Kill,***
***7 Barriers***

***Hannacroix Creek***
***5 Barriers***

***Black Creek***
***9 Barriers***

***Minisceongo Creek***
***7 Barriers***

***Peekskill Hollow***
***4 Barriers***

-  232 of 1938 captured

**Notes:**
Talk about methods here: electrofished, Binomial Depletion Method, stratified random subsample, otoliths removal, and swimbladder dissection

## Slide 4

| Table 1: Watershed Characteristics for Censused Hudson River Tributaries |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- |
| Tributary Name | Watershed | Stream  | Eel | Number of | Distance to  | % Artificial |
|  | Area (km2) | Length (km) | Penetration (km)a | Barriers | 1st Barrier (m) | Barrier |
| Wynants Kill | 85.47 | 25.95 | 5 | 7 | 20 | 43 |
| Hannacroix Creek | 166.24 | 37.81 | 31 | 4 | 1985 | 40 |
| Saw Kill | 66.29 | 22.62 | 11 | 7 | 255 | 43 |
| Black Creek | 87.77 | 29.55 | 27.5 | 9 | 2620 | 22 |
| Peekskill Hollow | 135.51 | 28.11 | 23.5 | 4 | 3825 | 100 |
| Minisceongo Creek | 47.9 | 18.86 | 9 | 6 | 1900 | 100 |
| 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.)

- _Barriers: An Important Role__(cont’d.)_

## 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

## Size Distribution

**Length of Hudson River mainstem eels**

**Notes:**
Make sure to mention dramatic difference between mainstem & tribs (mainstem average length of ~450 mm vs. our average of 185 mm)
Tribs can be viewed a nursery area

## Size matters!

- _Size matters!_

- 355  594 317  215 202         35   22

-    8     4     2     1

- 131

- 22   12   15

**Notes:**
Walk people through graph – a breakdown of frequency graph

## Eel Condition

-     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

**Notes:**
Error bars are 1 S.E.
BII partially addresses the 1/19/06 Threat Characterization - Barriers to upstream migration 

## Impacts of Barrier Intensity

-  As barrier intensity increases, eels able to reach these habitats grow faster

**Notes:**
As barrier intensity increases, surprisingly so does eel growth
Remember to tell that BII is a function of barriers/km and cumulative dam height

## 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

**Notes:**
During talk make sure to define P & I

## 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

- - http://www.dnr.cornell.edu/hydro2/hmap.gif

- 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 = 3.2-23.7

**Notes:**
No North-South gradient found
Mention that intensity not correlated to eel length
But then, what is? Well, next slide...

## Country Eels?

-  Not significant (p = 0.14) but an upward trend as urbanization increases

-  What does this mean?

**Notes:**
A threshold of roughly 15% seems to be important...
RELATE back to Riparian urbanization for eel condition
Can mention that nematode Abundance can be predicted by Barrier # and subcatchment urbanization (r2 = .48, p < .001)

## The Silver Lining...

-  Barriers are slowing nematode invasion

**Notes:**
Error bars are 1 S. D.

## Eel Condition

-  No significant difference

**Notes:**
Two codifiers:
 Intensity lower than found in other tributaries
 Yellow phase only – does not address silver eels

## 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

**Notes:**
By eel health make sure to note condition AND Anguillicola parasitizing as a transition between the two

## 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

## Questions?

- http://www.nanfa.org/akiweb/974.JPG