Transcript Document 7288272

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?
Wynants Kill,
7 Barriers
Hannacroix Creek
5 Barriers
Black Creek
9 Barriers
Stratified random
sampling for lab
analysis
− 232 of 1938
captured
Saw Kill,
7 Barriers
Peekskill Hollow
4 Barriers
Minisceongo Creek
7 Barriers
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
18000
Eel Density
Saw Kill
15000
Hannacroix Creek
12000
Black Creek
Multiple Barriers
Single Barrier
9000
6000
3000
0
0
5000
10000
15000
20000
Distance Upstream (m)
25000
30000
Barriers: An Important Role(cont’d.)
Eel Density
14000
12000
Minisceongo Creek
Peekskill Hollow
10000
Wynants Kill
Multiple Barriers
8000
Single Barrier
6000
4000
2000
0
0
5000
10000
15000
Distance Upstream (m)
20000
25000
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
140
100
Length of Hudson River mainstem eels
80
60
40
20
Eel Total Length (mm)
700
650
600
550
500
450
400
350
300
250
200
150
100
0
50
Frequency
120
8
4
2
1
650
700
850
22 12 15
80%
60%
40%
Below 2nd Barrier
Above 2nd Barrier
100
350
20%
Eel Total Length (mm)
550
500
450
400
300
250
200
150
0%
50
Proportion of Total .
100%
355 594 317 215 202 131 35 22
600
Size matters!
Eel Condition
Standardized residuals of eel wet weight
Eel Condition
0.2
Percent Riparian
regressed
totalUrbanization
length
0-10%
10-20% against
20-30%
40+%
Determined
-0.1
-0.2
Analysis
Ex.) An eel of -1 is 1 S.by
D.Gap
lighter
than average
0.1
0.0
-0.3
-0.4
Riparian Urbanization
0.2
BII = Barrier Intensity
Index

BII  Barriers / km * Cumulative Barrier Height
2

Eel Condition
0.0
-0.2
0
0-100
100-500
-0.4
-0.6
-0.8
-1.0
-1.2
BII Class
500-1000
Impacts of Barrier Intensity
7
2
LN Total Length (mm)
BII>100: Ln(TL) = 0.8156(Ln Age) + 4.1468; R = 0.76
6.5
BII = 0
6
BII = 0.1-100
BII = 100+
5.5
5
BII0.1-100: Ln(TL) = 0.6128(Ln Age) + 4.4842; R 2 = 0.85
2
BII0: Ln(TL) = 0.5667(Ln Age) + 4.3435; R = 0.90
4.5
4
0
0.5
1
1.5
2
2.5
3
3.5
LN Age (yrs.)
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 3.2 - 23.7
nematodes/eel
Tributary Invasion
2003 & 04 Sampling
Range = 0-20
nematodes/eel
Prevalence (P) =
39.2%
Intensity (I) = 2.44
nematodes/infected eel
Morrison and Secor, 2003
Prevalence = 60%
Hannacroix
P = 35.7%
I = 2.60
Black Creek
P = 31.6%
I = 2.25
Wynants Kill
P = 51.9%
I = 2.36
Saw Kill
P = 34.5%
I = 1.70
Minisceonga
P = 40.4%
I = 2.57
Peekskill
P = 43.6%
I = 2.77
Intensity = 3.2-23.7
- http://www.dnr.cornell.edu/hydro2/hmap.gif
2.5
Watershed Urbanization
Abundance
1.5
1.0
0.5
M
in
isc
eo
ng
o
ll
Ki
w
W
yn
an
ts
ll H
ol
lo
ll
Ki
Pe
ek
sk
i
Sa
w
Ha
nn
ac
ro
ix
0.0
C
ac
k
Bl
2.0
Mean Abundance
45%
40%
35%
30%
25%
20%
15%
10%
5%
0%
re
ek
Watershed Urbanization
Country Eels?
Not significant (p = 0.14) but an upward
trend as urbanization increases
What does this mean?
50
45
40
35
30
25
20
15
10
5
0
6.0
Prevalence
5.0
Intensity
4.0
3.0
2.0
Mean Intensity .
Prevalence (%) .
The Silver Lining…
1.0
0.0
0
1
2
3
4
5
6
7
8
9
Barriers Crossed
Barriers are slowing nematode invasion
Eel Condition
0.5
Eel Condition
0.4
0.3
Healthy
0.2
Infected
0.1
0
-0.1 0
200
400
-0.2
-0.3
Total Length
No significant difference
600
800
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 request @
[email protected]
Questions?
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