american eels in the hudson river estuary: from glass to silver · • quick summary of previous hr...
TRANSCRIPT
American eels in the Hudson River estuary: from glass to silver
Karin E. Limburg, SUNY ESF Chris Bowser, Sarah Mount
Hudson River National Estuarine Research Res. NYSDEC Hudson River Estuary Program
Bob Schmidt (in absentia)
Outline of today’s talk:
• General biology of eel (emphasis on )
• Quick summary of previous HR eel studies
• Current HR eel studies
• Glass
• Yellow
• Silver
• Evolution from study object to a river icon that brings people together
Freshwater eels are catadromous – born at
sea, can migrate into estuaries, rivers, streams, lakes…even stay at sea
Eels have a complex set of life stages:
Larvae – specialized to drift, called leptocephali (pl.)
Transform in estuaries into transparent glass eels
Develop yellow-brown pigmentation – called elvers
bootlace eels yellow phase silver (maturing,
migrating back to sea)
It wasn’t until an enterprising Dane, Johannes Schmidt, began a long-term examination of fisheries collections that we understood the life cycle of eels.
Beginning in 1904, Schmidt received grants from the Danish queen to send out ships into the middle of the Atlantic, to collect fish larvae.
Finally, in 1922, the smallest larvae were collected south of Bermuda in the Sargasso Sea…the mysterious part of the Atlantic with depths over 5,000 meters.
The further the ships went into the heart of the Atlantic, the smaller the leptocephali.
www.jang-eo.co.kr/a1.html
Source: Maryland Sea Grant
Source: Uwe Kils, Rutgers University
American eel leptocephali
Tesch, 1977
Capable of climbing vertical surfaces – capillary action - “glass walls” of old
Now, heavily exploited fishery
Source: Glooskap and the Frog
Glass eels swim up estuaries in droves
Yellow eels (growth phase)
• can live in a wide variety of habitats
• varied diets (leads to morphological variation their skulls)
• growth rates highly variable
• accumulate fat for the long migration back to Sargasso
As eels become ready to migrate to the Sargasso, they become silvery and their eyes enlarge – cease feeding
Pankhurst’s index = a measure of eye size (a maturation index)
Source: van Ginneken & van Theillart, U. Leiden
American eel life history
DFO Canada Scientific American
Age vs length
25
35
45
55
65
0 5 10 15 20 25 30
Age (years)
Le
ng
th (
cm
)
Gwb Hav New King Ath Alb
ALBANY
ATHENS
KINGSTON
km
245
200
145
105
55
20
salt
front
HAVERSTRAW
NEWBURGH
G.W. BRIDGE
Hugely variable growth rates!
Early HR eel studies
Hudson River yellow eel study 1997-99
– W. Morrison & D. Secor, U. MD
GWB eel#33, length = 49 cm
Example of variable growth seen in eel otoliths
Kingston eel#36, length = 45 cm
Source: Wendy Morrison, U. MD
Hudson River km 20
Hudson River km 145
Estuarine growth (fast)
Upriver/tributary growth
Hudson River tributaries study
2003-04 … the first,
featuring Leonard Machut (ESF M.Sc.)
Natural and artificial barriers act as filters that reduce the numbers of eels upstream
The Glass Eel Story, or The Young and the Wiggly
The Hudson River Glass Eel Project Albany
NYC
• Spans 150 miles of tidal estuary from Staten Island (salt) to near Albany (fresh)
• Variety of methods, sites, and audiences
• Springtime focus on YOY/glass eels/elvers
Using fyke nets to monitor glass eels
• Each spring, nets are placed in the mouths of streams • Teams of trained volunteers catch, count, and release eels • Project follows ASMFC methods
450,000+ juvenile eels caught &
released above barriers since 2008
550 volunteers at 12 sites in 2016
2388 8561 9303 7382
61555
90929
41816 48158
140942
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000
160,000
2008 2009 2010 2011 2012 2013 2014 2015 2016
Total glass eel catch for all sites
Average Eels Caught Per Day Per Year
15
41 29
18
125
203
93
110
239
0
50
100
150
200
250
300
2008 2009 2010 2011 2012 2013 2014 2015 2016
38
58
64
75
67
46
66
58
75
0
10
20
30
40
50
60
70
80
2008 2009 2010 2011 2012 2013 2014 2015 2016
Average Glass Eels/Day at Furnace Brook
Albany
NYC
22
51 38
10
106 125
311
184
428
0
50
100
150
200
250
300
350
400
450
2008 2009 2010 2011 2012 2013 2014 2015 2016
Average Glass Eels/Day at Fall Kill
Albany
NYC
22
51 38
10
106 125
311
184
428
0
50
100
150
200
250
300
350
400
450
2008 2009 2010 2011 2012 2013 2014 2015 2016
Average Glass Eels/Day at Fall Kill
Furnace Brook range: 38-75 glass eels/day
Albany
NYC
0
400
800
1200
1600
2000
3/25 4/4 4/14 4/24 5/4 5/14 5/24
Albany
NYC 4/14
Number of glass eels per collection period (approx. 24 hours)
0
400
800
1200
1600
2000
3/25 4/4 4/14 4/24 5/4 5/14 5/24
Minisceongo Creek
Albany
NYC 4/14
4/21
Number of glass eels per collection period (approx. 24 hours)
0
400
800
1200
1600
2000
3/25 4/4 4/14 4/24 5/4 5/14 5/24
Richmond Creek
Minisceongo Creek
Crum Elbow Creek
Albany
NYC 4/14
4/21
5/4
Number of glass eels per collection period (approx. 24 hours)
0
400
800
1200
1600
2000
3/25 4/4 4/14 4/24 5/4 5/14 5/24
Richmond Creek
Minisceongo Creek
Crum Elbow Creek
Saw Kill
Albany
NYC 4/14
4/21
5/6
5/10
In 2014 we tracked the speed of glass eels upriver
10.7
4.8
2.4
Date, 2014
# e
els
per
day
29
“Eel Mop” at Saw Mill River
“Eel-evators” to get eels past dams (May-Oct)
# Eels caught at Furnace Brook Ladder in 2011 & 2012 (sampling season May through October)
< 8 8-15 15-30 >30
2011
2012
Eel lengths in centimeters
“Assessing Provenance and Maturity Status of Hudson River Eels”
Yellow phase HR eels: Provenance studies using otolith chemistry
Artificial tag
An eel otolith (Photo: L. Machut)
Otoliths
(“ear-stones”)
An eel otolith (11-12 yrs old)
Here, we show results of analyzing the outermost 100 microns of material for 7 element/Calcium ratios + 26/24Mg isotopes…next slide…
Plot of Can2*Can1$Tributary. Symbol used is '*'. „ƒˆƒƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒƒˆƒƒ† Can2 ‚ ‚ ‚ ‚ 4 ˆ ˆ ‚ ‚ ‚ * Indian Kill ‚ ‚ ‚ ‚ ‚ ‚ Indian Kill Black Creek * ‚ 2 ˆ * * Crum Elbow Kill Black Creek * ˆ ‚ Crum ElbownKill Kil** *rum Elbow Kill ‚ ‚ Indian Kil* * *Indian Kill ‚ ‚ Indian Fal* *illIn*ian*KVlockie Kill ‚ ‚ Crum Elbow*Killn*Cru*KEl*ow Kill ‚ ‚ Crum Elbow Kill***aVlocill*K*lC*um Elbow Kill Black Creek * ‚ 0 ˆ Fall Crum *lbowVlo*l*eCrumlElbow Kill * Vlockie Kill ˆ ‚ Fall Kill** Indi*n **Crum Elbow K*lVlockie Kill ‚ ‚ Fall Kill*Indian*Kill * Black *reek ‚ ‚ Fall*KFall*Kill Vlockie Kill ‚ ‚ * Fall Kill Fall*Kill * Minisceongo Creek ‚ ‚ Minisceongo*Creek ‚ -2 ˆ Minisceon*oMinieceongo Creek ˆ ‚ Crum Elbow Kill * * Minisceongo Creek ‚ ‚ * Fall Kill ‚ ‚ * Minisceongo Creek ‚ ‚ * Minisceongo Creek ‚ ‚ ‚ -4 ˆ ˆ ‚ ‚ ŠƒˆƒƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒƒˆƒƒŒ -4 -2 0 2 4 6 Can1 NOTE: 1 obs hidden. 63 label characters hidden.
BC
CE
FK
IK
MC
VK
Canonical Discriminant Analysis of 53 eels
(Apologies for SAS output!)
Number of Observations and Percent Classified into Tributary
From Tributary
Black
Creek
Crum
Elbow
Kill
Fall
Kill
Indian
Kill
Mini-
sceongo
Creek
Vlockie
Kill Total
Black Creek 4
100%
0
0.00
0
0.00
0
0.00
0
0.00
0
0.00
4
100.00
Crum Elbow Kill 0
0.00 13
100%
0
0.00
0
0.00
0
0.00
0
0.00
13
100.00
Fall Kill 0
0.00
0
0.00 11
100%
0
0.00
0
0.00
0
0.00
11
100.00
Indian Kill 0
0.00
0
0.00
0
0.00 12
100%
0
0.00
0
0.00
12
100.00
Minisceongo Creek 0
0.00
0
0.00
0
0.00
0
0.00 7
100%
0
0.00
7
100.00
Vlockie Kill 0
0.00
0
0.00
0
0.00
0
0.00
0
0.00 6
100%
6
100.00
Total 4
7.55
13
24.53
11
20.75
12
22.64
7
13.21
6
11.32 53
100%
Priors 0.16667
0.16667
0.16667
0.16667
0.16667
0.16667
All 53 eels were correctly classified to the tributary where they were captured
Photos: Dave Yozzo
Silver Eel Studies
1. American eels (Anguilla rostrata) hatch here
Béguer-Pon et al. 2015
Tagging adult eels
Béguer-Pon et al. 2015
Silver eel research Goals:
• Better understand transition from yellow (resident) to silver (migratory)
• Develop a non-lethal index of maturity for American eels that can be used by researchers and managers
Why? To easily assess eel productivity in the field based on quantitative measures
Methods
NYC
Electrofishing
Fyke netting
Albany
NYC
External measurements (≥25cm) • Total length • Wet weight • Horizontal and vertical
eye diameter • Head length • Head width • Pectoral fin length • Body depth
Clusters by size
± S.E.
0
100
200
300
400
500
600
700
SilverF SilverM Yellow YellowF
Tota
l len
gth
, mm
Maturity class
Clusters by eye and fin index
0
2
4
6
8
10
SilverF SilverM Yellow YellowF
Pan
khu
srt
eye
ind
ex
• Pankhurst eye index separates eels into mature (silver) or immature (yellow) • Threshold = 6.5
• Mature eels have higher eye index, above threshold
Clusters by eye and fin index
0
2
4
6
8
10
SilverF SilverM Yellow YellowF
Pan
khu
srt
eye
ind
ex
0
1
2
3
4
5
6
SilverF SilverM Yellow YellowF
Pect
ora
l fin
ind
ex
• Pankhurst eye index separates eels into mature (silver) or immature (yellow) • Threshold = 6.5
• Mature eels have higher eye index, above threshold
• Fin index also significantly different between silver and yellow eels
Discriminant analysis • Correctly classify individuals 83% of the time overall
Predicted maturity stage
SilverF SilverM1 SilverM2 Yellow1 Yellow2 YellowF1 YellowF2 Total
SilverF 13
87%
0
0%
0
0%
0
0%
0
0%
0
0%
2
13.33%
15
SilverM1 0
0%
17
94%
1
5.56%
0
0%
0
0%
0
0%
0
0%
18
SilverM2 0
0%
0
0%
17
85%
0
0%
3
15%
0
0%
0
0%
20
Yellow1 0
0%
1
0.5%
2
1%
160
80%
34
16.92%
4
1.99%
0
0%
201
Yellow2 0
0%
1
2.04%
0
0%
2
4.08%
46
94%
0
0%
0
0%
49
YellowF1 1
5.88%
0
0%
0
0%
2
11.76%
0
0%
12
71%
2
11.76%
17
YellowF2 0
0%
0
0%
0
0%
1
12.5%
0
0%
0
0%
7
88%
8
Act
ual
matu
rity
sta
ge
Mark-Recapture on the Indian Kill
So far we’ve: • Tagged 347 eels • Recaptured 110
eels at least once
Methods allow us to investigate: • Growth
(~1 cm/year) • Movement
(62% don’t move) • Maturity
Albany
NYC
Data Story of Eel Maturity
July, 2014 4x4 mm eye diameter 14 mm fin length
Marsh
Albany
NYC
Data Story of Eel Maturity
July, 2014 4x4 mm eye diameter 14 mm fin length
October, 2014 6x6 mm eye diameter 17 mm fin length
Marsh
Albany
NYC
Data Story of Eel Maturity
July, 2014 4x4 mm eye diameter 14 mm fin length
October, 2014 6x6 mm eye diameter 17 mm fin length
Marsh
Heading to the Sargasso!
Albany
NYC
Timing of maturity clusters
0
10
20
30
40
50
60
70
80
90
100
Jul 2013 Aug 2013 Sep 2013 Fyke 2013 Jul 2014 Aug 2014 Sep 2014 Fyke 2014
% e
els
cau
ght
SilverF SilverM Yellow
Summary of silver eel research • Research tools important in future studies
• Non-lethal maturity index has fairly high classification rates
• Could be used in future studies to: • Assess eel productivity – how many mature eels out of
total numbers
• Paired with data on other life stages, could calculate survivorship from one life stage to the next
• Compare maturity breakdown in different habitat types
Respect Your Elvers!
Evolution from study object to a river icon
that brings people together…
Respect Your Elvers! Evolution from study object to a river icon
that brings people together…and reconnects waters
Respect Your Elvers! Evolution from study object to a river icon
that brings people together…and reconnects waters
Working with students and volunteers!
“There is life against all odds in places where you would think there is nothing. Interesting opportunities exist in the scientific
community for amateur naturalists to make a contribution.” --volunteer Eva Schadeck
“At first, I only did it for extra credit, but then I realized it was really cool!”
--Poughkeepsie High School student
Thank you for listening!
Thank you, HRF, NYSDEC, and especially Cara Ewell Hodkin and Kayla Smith for helping with oto-analyses
Bob Schmidt
External cluster analysis
• 983 individuals total
• Separated into 7 significantly different clusters
Using fyke nets to monitor glass eels
• Each spring, nets are placed in the mouths of streams • Teams of trained volunteers catch, count, and release eels • Project follows ASMFC methods •http://www.youtube.com/watch?v=j-tik6Y9ztA •http://www.youtube.com/watch?v=gfCvxIgSw_s