HomeMy WebLinkAboutAL Interim Fisheries Report_January 2022
K:\018641-000\Admin\Docs\018641-000 MEMO September 2021 Fisheries survey Draft 178 E 9TH STREET | SUITE 200 | SAIN | 55101 | 651.286.8450 | WSBENG.COM
Memorandum
To: Jessica Vanderwerff Wilson
From: Jordan Wein, WSB
Date: January 14, 2022
Re: Arrowhead Fisheries Survey
Edina, MN
WSB Project No. 018641-000
BACKGROUND
Arrowhead Lake (MN DNR DOW #27004500) located in Edina, MN is a 22-acre lake with an
average depth of 4.5 feet with a maximum of 7 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 with 3
diffusers near the southeast area of the lake were installed in 1994 to attempt to maintain a
healthy fishery through conditions that usually result in hypoxia in the lake (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.
A standard MN DNR fishery was completed in 1995 and showed a species diversity of black
bullhead, green sunfish and fathead minnows using standard trap nets. This diversity seems to
suggest regular periods of hypoxia since these species are especially resistant to low levels of
dissolved oxygen. MN DNR permitted stocking of 400 bluegill sunfish and 600 largemouth bass
(both species susceptible to mortality in hypoxic conditions) occurred in 1994 by lake residents,
however no fish from that stock was recaptured indicating low or no survival of stocked species.
Since then, in 2016, the lake was stocked with 1000 bluegill fingerlings and 1000 yearlings as
well as 430 largemouth bass fingerlings and 90 yearlings. No MN DNR survey has been
conducted since then.
This memo describes the use of nets to conduct a standard fisheries survey at Arrowhead Lake in
Edina, MN. The results 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.
Fall 2021 Fisheries Survey Memo
January 14, 2022
Page 2
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
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
bullhead, bluegill sunfish, green sunfish, hybrid sunfish, and largemouth bass as shown in Figure
2.
Fall 2021 Fisheries Survey Memo
January 14, 2022
Page 3
Figure 2: Largemouth bass on left and bluegill on right from traps
Figure 3: Catch per unit effort (CPUE) by species and trap type in 2021.
0
20
40
60
80
100
120
Black bullhead Bluegill Green sunfish Hybrid sunfish Largemouth
bassNumber of fish caughtSpecies
Mini TrapNet
Standard TrapNet
Fall 2021 Fisheries Survey Memo
January 14, 2022
Page 4
Figure 4: Average length by species and trap type in 2021.
0
2
4
6
8
10
12
14
16
18
Black bullhead Bluegill Green sunfish Hybrid sunfish Largemouth
bassAverage length (inches)Species
Mini TrapNet
Standard TrapNet
Fall 2021 Fisheries Survey Memo
January 14, 2022
Page 5
Figure 5: CPUE comparison of MN DNR survey in 1995 and WSB survey in 2021 using standard trap nets.
For comparison purposes, the following will focus the CPUE only from standard trap nets since
both the 1995 and 2021 surveys used standard sizes. The most abundant species was bluegill
sunfish with a CPUE of 18.17 and an average size of 5.8 inches. Next most abundant was
largemouth bass with a CPUE of 2.17 and an average size of 13.1 inches. Black bullhead and
green sunfish showed the same abundance with CPUE of 0.17 and an average size of 9.8 and
6.2 inches respectively.
0.00
20.00
40.00
60.00
80.00
100.00
120.00
140.00
160.00
Black bullhead Bluegill Green sunfish Largemouth bassCPUE
Species
1995 survey 2021 survey
Fall 2021 Fisheries Survey Memo
December 6, 2021
Page 6
K:\018641-000\Admin\Docs\018641-000 MEMO September 2021 Fisheries survey Draft 178 E 9TH STREET | SUITE 200 | SAIN | 55101 | 651.286.8450 | WSBENG.COM CONCLUSIONS
Preliminary results show a stark contrast between the two different surveys. The 1995 survey
captured species that are typical in lakes that suffer frequent winter kills due to hypoxia.
However, the turnover to species like bluegill and largemouth bass suggests stocking of these
species in 2016 was successful and there are normally abundant in Arrowhead Lake. Follow up
surveys in spring of 2022 will continue to establish the status of the fishery after an additional
winter has passed.
Fall 2021 Fisheries Survey Memo
January 14, 2022
Page 7
APPENDIX:
Figure 4:Map of aeration diffusers in Arrowhead Lake