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Memorandum
To: Jessica Vanderwerff Wilson
From: Jordan Wein, WSB
Date: January 14, 2022
Re: Indianhead Fishery Survey
Edina, MN
WSB Project No. 018642-000
BACKGROUND
Indianhead Lake (MN DNR DOW #27004400) located in Edina, MN is a 14-acre lake with an
average depth of 4.5 feet with a maximum of 6 feet. Hypoxia (lack of enough oxygen to support
living tissues) can occur in winter when ice and snow have prevented reintroduction of dissolved
oxygen to the lake. This can result in the observation of fish kills in springtime when ice melts off
the lake. In addition, in shallow lakes, hot and dry months in summer can deplete oxygen to the
point of summer fish kills. To prevent this, a common management option is to install aeration
systems to artificially add dissolved oxygen to the water column. An aeration system consisting of
4 aerators spread throughout the lake was installed in 1979 as part of a Clean-Flo system to
control algae and submerged plants. Furthermore, the aeration system served to prevent
conditions that usually result in hypoxia in the lake and fish winterkill. However, a lack of
knowledge of this fishery exists and thus the effect of the aerators is not well known. This system
is paid for by the lake association and maintenance is coordinated by the service contractor
through the City of Edina.
To this point, there has not been a standard MN DNR fishery assessment using standard trap
nets. Therefore, it is believed this is the first standardized survey efforts on the lake. In the last
10 years, MN DNR permitted stocking has occurred in 2013 and 2016, stocking native species
like bluegill sunfish (200 and 5000 respectively) black crappie, (50 and 2000 respectively) and
largemouth bass (200 and 1900 respectively). This stocking was paid for by lake residents. The
desire was to promote a healthy, native fisheries balanced for sustainable fish populations.
The results of these surveys will give a baseline index for catch per unit effort (CPUE) for
comparison of subsequent surveys in order to understand population and diversity dynamics as
well as presence/absence of invasive species. This event was conducted between September
19, 2021 through September 21, 2021.
ARROWHEAD TRAP NET SURVEYS: SEPTEMBER 2021
Methods
We used three (3) MN DNR standard double frame fyke trap nets with ¾” mesh and a 60’ lead
line. In addition, we used three (3) mini fyke trap nets with 3/8” mesh and a 30’ lead line (seen in
Figure 1). This style of traps targets the natural movement patterns of fish along the shorelines
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during a 24-hour period. Fish swimming along the shore is guided toward funneled throats the
allow the fish in but is not able to escape. The contents of each trap are emptied, all fish are
identified, and a representative sample is measured for length for comparative purposes.
Figure 1: Example of mini fyke trap net set in a lake.
Results
Both standard trap nets and mini fyke trap nets resulted in the same diversity of species: black
crappie, bluegill sunfish, golden shiner, hybrid sunfish, and largemouth bass as shown in Figure
2. The most abundant by far were bluegill sunfish with an average size of 6.7 inches, followed by
hybrid sunfish at an average length of 8.2 inches, then black crappie at 7.3 inches, golden shiners
at 6.9 inches and finally largemouth bass at 10.6 inches (see Figures 3 and 4 below).
Figure 2: On the left, snapping turtles were regularly caught in out traps as well as bluegills, black crappie
and golden shiners shown on the right.
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Figure 3: Total fish captured by species and trap type in 2021.
Figure 4: Average length by species and trap type in 2021.
0
100
200
300
400
500
600
Black crappie Bluegill Golden shiner Hybrid sunfish Largemouth
bassNumber of fish caughtSpecies
Mini TrapNet
Standard TrapNet
0
2
4
6
8
10
12
Black crappie Bluegill Golden shiner Hybrid sunfish Largemouth
bassAverage length (inches)Species
Mini TrapNet
Standard TrapNet
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Figure 5: CPUE comparison of MN DNR survey in 1995 and WSB survey in 2021 using standard trap nets.
CONCLUSIONS
Preliminary results support the assumption that the stocking efforts in 2013 and 2016 were
successful and recruitment (survival of fish spawned within the lake) could be occurring.
However, the lack of abundant small fish (<3 inches) may suggest low recruitment, but high
survival of stocked fish. Regardless, the fishery seems to have benefitted from stocking efforts
and the installation of aeration systems. However, data from dissolved oxygen surveys will help
to study the effect over an entire year (data to come in final report). Follow up fishery surveys in
spring of 2022 will continue to establish the status of the fishery after an additional winter has
passed.
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APPENDIX
Figure 4: Map of aerator diffusers in Indianhead Lake