Red Swamp Crayfish - Germantown
Executive Summary
By Andrew Notbohm
Water Resources Management Specialist, Wisconsin DNR
December 19, 2013
Discovery – August, 2009
In late August, 2009 the Wisconsin Department of Natural Resources (WDNR)
received a report about a possible invasive crayfish species inhabiting a 4.88 acre
stormwater pond in the Esquire Estates community in the Village of Germantown,
Wisconsin. The report was investigated and it was determined that the red swamp
crayfish had established itself in this pond. This was the first documented discovery of
this species in Wisconsin. Because red swamp crayfish are considered to be one of the
most invasive crayfish species in the world, the WDNR felt it was necessary to act
quickly. Many different methods were used to control this pest, as effective invasive
species eradication/control generally is not successful with a single method.
Initial Monitoring – Fall, 2009
During the fall of 2009, 2,390 red swamp crayfish were captured and removed
from the Esquire Estates Pond. Hand netting resulted in the removal of 247 of these
crayfish while 2,143 crayfish were removed via minnow traps. The catch per unit effort
(CPUE) of the minnow traps was 0.19 crayfish/day*trap. In addition to capturing red
swamp crayfish from the Esquire Estates Pond, nearby ponds were also monitored for the
presence of this species. Red swamp crayfish were found in a small pond located next to
the Germantown Police station. This pond was connected to the Esquire Estates Pond via
a drainage ditch that meandered through Ashbury Woods. A barrier constructed out of
Nicotarp was installed around the entire Esquire Estates Pond and Police Pond to prevent
emigration.
Chemical Treatment and Drawdowns – Fall, 2009-Winter, 2009-2010
On November 12, 2009, the WDNR treated the Esquire Estates Pond with San-IKing which is a 12.5 percent bleach solution. The pond received 500 gallons of product
to reach a concentration of 50 ppm. Burrows created by red swamp crayfish were
identified and were treated with a 200 ppm solution of this product. The Police Pond was
also treated with San-I-King at the same rate as Esquire Estates Pond. Post treatment
monitoring was performed in late fall, 2009 which resulted in the capture of zero
crayfish. Throughout the winter of 2009-2010, the Esquire Estates pond was held below
normal water level and the Police Pond was drawn down via pumping with the goal of
freezing burrowed crayfish.
Fish Stocking and Crayfish Monitoring – Spring, 2010
In May, 2010, Fisheries staff stocked the Esquire Estates Pond with largemouth
bass, smallmouth bass and rock bass to help control the remaining red swamp crayfish
population through predation. Esquire Estates Pond was monitored with traps April
1
through June, 2010. During this time, 120 red swamp crayfish were caught and removed.
Total Average CPUE data is not available for this time period. This data indicated that
the mechanical removal and chemical treatment performed in fall, 2009, the drawdown
performed throughout the winter of 2009-2010 and the fish stocking performed in spring,
2010 contributed to a 90% decline in the red swamp crayfish population.
Funding Issues and Police Pond Chemical Treatment – July-December, 2010
Due to the intensive work performed up to this point, funding was limited during
this six month period in 2010. Funds were secured, however, to perform a second
chemical treatment on the Police Pond. In November, 2010, Fisheries Staff treated the
Police Pond with Pyronyl 303. Pyronyl is a botanical pesticide labeled for use in the
United States in wetlands and terrestrial environments, but not ponds. Therefore, a
Federal permit was needed to apply this product to the Police Pond. Pyronyl was the
desired chemical to use during the Esquire treatment but the necessary permit was not
obtained in time. After the Pyronyl treatment, the Police Pond was routinely dewatered
to keep it as dry as possible throughout the winter of 2010-2011 to increase the effect
freezing would have on any crayfish that burrowed prior to the treatment.
Monitoring – Summer, 2011
Students from the Wisconsin Lutheran College were hired and trapping resumed
in the Esquire Estates and Police Ponds to evaluate the success of the 2010 efforts. Due
to the timing of the chemical treatment and the inability to maintain the dewatered state
of the Police Pond, red swamp crayfish were captured in the Police Pond throughout
2011. Between May and September, 2011, 40 red swamp crayfish were captured and
removed from the Police Pond with a CPUE of 0.02. During the same time span, 918 red
swamp crayfish were captured and removed from the Esquire Estates Pond with a CPUE
of 0.17. Other nearby waters within a mile were monitored, including 13 ponds and the
Jefferson Ditch tributary to the Menomonee River but no red swamp crayfish were
captured.
Great Lakes Restoration Initiative Grant – Late Summer, 2011
In August/September, 2011 the WDNR was awarded a $286,843.00 grant from
the United States Environmental Protection Agency to attempt eradication of the red
swamp crayfish population.
Filling In Police Pond – October, 2011
A portion of the recently acquired grant was used right away as WDNR staff from
Fisheries, Water Resources, and Equipment Operations as well as staff from the Village
of Germantown worked together to fill in the Police Pond, thus eliminating red swamp
crayfish from this site. The pond was dewatered and amphibians and reptiles were
transferred to the adjacent Ashbury Woods. Next, the banks were excavated and the
material was used to mix with the bottom sediments of the pond. Finally, the pond was
filled in with crushed road millings and compacted to crush and/or encapsulate any
remaining crayfish.
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Monitoring – Summer, 2012
The Esquire Estates Pond and the Ashbury Woods ditch were monitored with
traps April through October, 2012. During that time, 2,480 red swamp crayfish were
captured and removed from Esquire Estates Pond. Average CPUE for this time period is
not available but catch rates were highest in late June and July when water temperature
was warmest. Eleven nearby ponds within a mile of Esquire Estates were monitored in
2012; all were negative for red swamp crayfish. Two additional sites on the Menomonee
River were sampled in 2012; both negative for red swamp crayfish.
Development of Final Eradication Plan – June-September, 2012
Up to this point, much work had been done to eliminate this pesky invasive
species. Red swamp crayfish had been trapped, poisoned, and their habitat had been
removed but they still were present in the Esquire Estates Pond and potentially present in
the adjoining Ashbury Woods ditch. To address this issue, an eradication plan was
conceived though many meetings and intensive experiments. Construction contractors
and a worldwide crayfish expert from the U.K. assisted in the development of the plan.
The resulting strategy included a large scale shoreline and ditch manipulation in the
Esquire Estates Pond and Ashbury Woods ditch. In addition to the manipulations, a
second Esquire Pond chemical treatment was scheduled to take place following
construction completion. Similar to the second Police Pond treatment, the second
Esquire Pond treatment would use Pyronyl instead of bleach.
Ashbury Woods Construction – October, 2012
The first phase of the eradication plan included a manipulation of the drainage
ditch in Ashbury Woods from the outlet of the former Police Pond to the culvert at
Western Ave. WDNR Fisheries, Water Resources and Wildlife staff cleared a swath on
both sides of the ditch to maneuver equipment. Skid loaders were used to scrape a more
defined channel through the woods which would hold the majority of future water flow.
Once the channel was shaped, 12 ounce road construction fabric was placed in the
channel and on the perimeter of the channel. This fabric was used because it was
determined that red swamp crayfish could not penetrate it when burrowing. After the
fabric was placed, approximately five inches of crushed number two limestone was
spread across the fabric. Crushed number two limestone was used because it was
determined that this would prevent the burrowing of any red swamp crayfish. Lastly,
after the channel was rocked, any disturbed areas were seeded and covered with erosion
control fabric.
Esquire Estates Construction-Phase I – November-December, 2012
Similar to the Ashbury Woods project, the banks of the Esquire Estates Pond were
excavated to disturb any crayfish burrows and shaped to create a slope that would allow
the placement of fabric and rock. A contractor was hired to perform the construction
work on the island which consisted of brushing and excavating the banks and placing the
12 ounce road fabric and three to six inches of number two stone in a 15-20 foot wide
band around the entire 899 feet of the island. WDNR Fisheries, Water Resources and
Equipment Operations staff worked on the perimeter of the pond which included
excavating and shaping the bank as well as placing the 12 ounce road fabric and four to
3
eight inches of number two stone in a 10-25 foot wide band around 1,450 feet of bank.
To accomplish this, an access road was first carved out at the base of the bank and the
bank shaping, fabric and rock work was done in a retreating fashion. In addition to the
pond itself, WDNR staff performed the same procedure on the inlet to the pond placing
the fabric and rock in a 132 foot band 15-20 feet wide. Unfavorable winter weather
conditions forced work to be stopped in mid-December, 2012. Completion of the project
was then planned for 2013.
Monitoring – Summer, 2013
Traps were set in the Esquire Pond May through August 2013. Thanks in part to
the bank modification work done the previous fall, only 39 red swamp crayfish were
captured throughout the 2013 sampling season for an average CPUE of 0.007. The
majority of these crayfish were captured along the shoreline of the pond that had not yet
been covered with fabric and rock. Once again, surrounding ponds and streams were
monitored with no red swamp crayfish observed.
Esquire Estates Construction-Phase II – Fall, 2013
In September, 2013, the same contractor that did the Esquire Pond island work
completed the remainder of the excavating, fabric and rock work, with the assistance of
some WDNR staff. A five to fifteen foot band was shaped (where needed) and lined with
fabric and four to eight inches of number two stone along 1,160 feet of shore. Due to
steep topography, the remaining 80 feet of shore received #3 rip rap stone on top of the
fabric instead of the number two crushed stone.
Esquire Estates Chemical Treatment – Fall, 2013
With the bank and channel modifications to the Esquire Pond and the Ashbury
ditch completed, the final phase of the eradication plan included another chemical
treatment to the pond, this time with Pyronyl. During this two day treatment, WDNR
Fisheries and Water Resources staff used a combination of spraying and injecting to
deliver the chemical to the pond and the surrounding banks, including the drainage ditch
between the former Police Pond and the Esquire Pond.
Post Chemical Treatment Monitoring – Fall, 2013
Following the chemical treatment, the pond was monitored to determine the
duration and the level at which the chemical persisted in the water. Water samples were
collected from two points within the pond (Figure 1) and tested for Pyrethrins. These
samples were collected for nearly one month post treatment and indicate that the entire
pond retained a high level of the chemical for at least five days (Table 1, Figure 1-2). In
addition to the water samples, water quality parameters were measured at the same points
as the water sample collections. This data is presented in table 2 and table 3. Finally,
bio-assays cages were used to assess the ability of crayfish and minnows to survive in the
pond. The cages were stocked with either crayfish or minnows and were checked
periodically to determine the condition of the specimens. Bio-assay crayfish continued to
die within a few hours of exposure up to three weeks after the treatment. The results of
4
the bio-assay cages and residual Pyrethrins water samples indicate that the chemical
treatment was a success.
Future Monitoring – Summer, 2014
As a result of the activities described above, the WDNR is hopeful that red
swamp crayfish have been eradicated from the Esquire Estates Pond, Police Pond,
Ashbury Woods ditch and have not spread to any nearby waterbodies. The Esquire Pond
and neighboring ponds and streams will be monitored May through August, 2014 to see
if this extremely invasive species has in fact been eradicated from this area.
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East Basin Sample Point
West Basin Sample Point
Figure 1. Ariel map of the Esquire Estates Pond. Water samples and water
quality measurements were taken from multiple depths at one point in the West
Basin and one point in the East Basin.
Table 1. Esquire Estates water sample Pyrethrins data following Pyronyl treatment
on September 17-18, 2013.
Sample Concentrations (ug/L)
West Basin
West Basin
East Basin
East Basin
Date
2 Feet
4 Feet
2 Feet
6 Feet
09/18/2013
410
340
410
370
09/19/2013 AM
420
410
380
280
09/19/2013 PM
360
330
410
340
09/20/2013 AM
290
250
300
300
09/20/2013 PM
290
250
260
270
09/23/2013
110
120
140
150
09/26/2013
34
34
10/02/2013
17
25
10/10/2013
1.4
3.3
10/16/2013
2.2
3.3
6
Figure 2. Water sample data from West Basin of Esquire Estates Pond
following Pyronyl treatment on September 17-18, 2013.
Figure 3. Water sample data from East Basin of Esquire Estates Pond following
Pyronyl treatment on September 17-18, 2013.
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Table 2. Water Quality Data from West Basin of Esquire Estates Pond.
September 12 2013
Depth
Temp
pH
DO
Cond
% Sat
3
24.69
8.95
9.16
1572
4.5
24.5
8.99
9.95
1570
September 18 2013
Depth
Temp
pH
DO
Cond
% Sat
2
19.28
8.98
11.39
1388
126.9
4
19.22
9
11.7
1386
128.9
September 19 2013 - AM
Depth
Temp
pH
DO
Cond
% Sat
2
19.94
8.96
11.99
1385
136
4
19.67
8.97
12.4
1387
140.1
September 19 2013 - PM
Depth
Temp
pH
DO
Cond
% Sat
2
20.02
8.99
11.71
1388
134
4
19.99
8.99
12.09
1390
139.2
September 20 2013 - AM
Depth
Temp
pH
DO
Cond
% Sat
2
21.12
8.9
9.9
1415
115.5
4
20.43
9
12.22
1451
140.8
September 20 2013 - PM
Depth
Temp
pH
DO
Cond
% Sat
2
21.7
8.91
1417
4
September 23 2013
Depth
Temp
pH
DO
Cond
% Sat
2
18.18
8.89
9.81
1433
107.8
4
17.97
8.95
11.04
1428
120.3
September 26 2013
Depth
Temp
pH
DO
Cond
% Sat
2
17.7
8.68
1374
4
17.69
8.72
1373
October 10 2013
Depth
Temp
pH
DO
Cond
% Sat
2
18.15
8.77
1288
4
17.44
9.03
1284
-
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Table 3. Water Quality Data from East Basin of Esquire Estates
September 12 2013
Depth
Temp
pH
DO
Cond
2
24.62
8.89
8.96
1576
4
24.4
8.86
8.5
1573
6
24.17
8.86
8.51
1574
September 18 2013
Depth
Temp
pH
DO
Cond
2
19.72
8.8
9.11
1391
4
19.04
8.81
9.06
1390
6
18.77
8.83
9.23
1390
September 19 2013 - AM
Depth
Temp
pH
DO
Cond
2
19.94
8.83
9.72
1389
4
19.11
8.88
10.82
1392
6
19
8.82
9.47
1394
September 19 2013 - PM
Depth
Temp
pH
DO
Cond
2
20.38
8.83
9.51
1393
4
19.19
8.81
9.4
1392
6
19.09
8.83
9.53
1392
September 20 2013 - AM
Depth
Temp
pH
DO
Cond
2
21.25
8.75
7.73
1396
4
19.71
8.82
8.92
1462
6
19.29
8.76
7.78
1464
September 20 2013 - PM
Depth
Temp
pH
DO
Cond
2
21.87
8.76
7.94
1398
4
19.76
8.8
8.91
1460
6
19.42
8.78
8.43
1461
September 23 2013
Depth
Temp
pH
DO
Cond
2
18.1
8.63
6.46
1436
4
17.74
8.64
6.53
1434
6
17.51
8.62
6.5
1435
September 26 2013
Depth
Temp
pH
DO
Cond
2
17.97
8.43
1380
4
17.41
8.46
1377
6
17.32
8.44
1379
October 10 2013
Depth
Temp
pH
DO
Cond
2
4
6
-
9
Pond.
% Sat
% Sat
102.2
99.9
101.2
% Sat
110.5
119
106.1
% Sat
108.7
102.5
106.4
% Sat
90.8
103.1
88.8
% Sat
94.6
101.6
96.8
% Sat
70.5
71.1
69.9
% Sat
% Sat
-