Distribution of the swimbladder parasite Anguillicola crassus in
American eels in the Northeastern Atlantic
University of Massachusetts Dartmouth
Department of Biology
Amy Aieta&
Kenneth Oliveira
Life History of Anguilla rostrata
Silver phase
EggLeptocephalus larvae
Glass eel/Elver
Yellow phase
L2 Released
Intermediate Host
L2 molts to L3
Intermediate/Paratenic Host
Ingested by Eel
L3-L4 swimbladder wall L4-L5 swimbladder lumen
The life cycle of Anguillicola crassus
Biogeography of Anguillicola crassus
•Identified in Southeast Asia 1974 •(Anguilla japonica)
•Early 1980s introduced to Europe •(Anguilla anguilla)
•1995 found in North America• (Anguilla rostrata)
Occurrence of A. crassus in North America
1995 Texas (TPWD; Moravec)
South Carolina (Fries et al. 1996)
Chesapeake Bay (Barse and Secor 1999; Barse et al. 2001)
Hudson River (Barse and Secor 1999)
2003 N. Dartmouth, MA
Objectives
1) Determine northern extent of parasite range in USA
2) Examine prevalence & intensity within NE
3) Examine effects of parasite/eel interactions
MethodsNortheastern Distribution
Yellow eels *
•Summer 2005
Southern Sampling Survey
•CT, RI, S.-MA
Northern Sampling
•N.-Ma, NH, ME
n=13
n=10
n=3
Collection of Yellow Eels in Freshwater
Collection of Silver Eels
• Eels euthanized w/Clove oil
• Weighed/length measured
• Parasites counted
• Parasite length measured
Preliminary Analysis
Analysis
Prevalence Example 30%
infected
Mean Intensity1.67 parasites
Results
69%
35%
28%
Prevalence of Infection: Rhode Island
N. KINGSTON
7%
33%62%
76%
16%
52%21%
58%64%33%
Prevalence of Infection: Massachusetts
NEW BEDFORD
PLYMOUTH
BOSTON
0%31%0%
0%0%0%
Prevalence of Infection: Maine
BANGOR
PORTLAND
0%
26%
35%60%
58%65%
53%
Kennebec RiverEstuarine eels
n = 315
Eel Size Class (cm)
<10
10.1
-15.
1
15.2
-20.
2
20.3
-25.
3
25.4
-30.
4
30.5
-35.
5
35.6
-40.
6
>40.
6
Mea
n P
aras
ite
Inte
nsi
ty
0
2
4
6
8
Log 10 Eel Length
1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0
Lo
g 1
0 E
el W
eig
ht
-2
-1
0
1
2
3
4Nonparasitized r2 = 0.99 (n = 523)
Parasitized r2 = 0.98 (n = 315)
Silver Eel Data: Paskamansett River
Year Prevalence Mean Intensity2003 28% 2.9
2004* 52% 5.8
2005 ? ?
SignificancePrevalence: Fischer's Exact Test p = .008
Intensity: T-test p = .007
Conclusions
Current Northern Limit
• Sedgeunkedunk Stream, ME • 44°45.306N, tributary of the Penobscot River
• No latitudinal trend• Possible ballast water introduction
• Temperature: not an apparent limiting factor
Influences of Parasite
• All size classes infected• No apparent detrimental effects on eel weight/length• Suspected negative impact on migrating silver eels
Questions/Discussion