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Fishery Survey – Middle Eau Claire Lake

Bayfield County, 2013 WBIC Code – 2742100

Bennett Nelson with walleye. Photo by: Lee Wiesner

Scott Toshner Senior Fisheries Biologist

Wisconsin Department of Natural Resources Northern District - Brule

May, 2014

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Executive Summary

The fisheries of Middle Eau Claire Lake (Bayfield County) were surveyed during 2013. Results

indicated adult walleye abundance (≥ 15 in and sexable fish) was 2.6 adults/acre, which represents a 49%

decline when compared to the average abundance of 5.1 adults/acre from 1991 to 2007. Walleye

abundance on Middle Eau Claire Lake was lower than the Bayfield/Douglas County average for naturally

recruiting walleye lakes, and the statewide management objective of 3.0 adults/acre. The walleye size

structure has changed significantly between survey periods and has increased as abundance has declined.

Smallmouth and largemouth bass abundance have increased; however, largemouth bass have increased at

a higher rate and now outnumber smallmouth bass. Muskellunge and northern pike were both present in

low abundance and were important to anglers as they relate to directed effort and harvest. Bluegill

relative abundance from 2013 has increased by 69% since 2004; however average length and growth of

bluegill has decreased, and is likely due to higher abundance of bluegill. The decrease in walleye and

yellow perch abundance and the increase of largemouth bass and bluegill abundance could be an

indication of a switch from a fishery dominated by pelagic species to one dominated by littoral species.

Angling pressure during the 2013-2014 fishing season was 16.0 hrs/acre which was the lowest for any

survey on Middle Eau Claire Lake and below average for Bayfield and Douglas County creel surveys. A

portion of the angling pressure decline in 2013 may be attributable to the poor ice conditions during the

ice fishing season. Walleye and muskellunge were the most sought after gamefish species with directed

efforts of 17% and 14% respectively. Anglers harvested 347 walleye and tribal spearers harvested 241

walleye in 2013. Estimated exploitation (sport angling plus tribal spearing) of walleye ≥ 15 in and

sexable was 15%. Management recommendations include, 1) Considering a more restrictive regulation

for walleye such as no minimum length limit and a no harvest slot of 14 to 18 in to further improve size

structure, while taking into consideration conservative regulation changes that are expected to go into

effect on Upper and Lower Eau Claire Lakes in 2016. A more conservative walleye regulation could be

expected to decrease angler harvest but not necessarily to increase walleye abundance due to angler

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exploitation likely not being a cause for walleye abundance declines on Middle Eau Claire Lake. Angler

preference data should be collected during the next creel survey scheduled for 2016, the analysis of which

will help inform decision making on whether or not to implement more restrictive walleye regulations.

Due to continued adequate natural reproduction, walleye stocking is not recommended unless future fall

electrofishing surveys decline below 10 young of the year walleye per mile for three consecutive years.

2) Changing existing bass angling regulations to provide increased opportunity for anglers to harvest

largemouth bass while implementing more restrictive regulations for smallmouth bass to protect the

excellent size structure, 3) Maintaining stocking of marked muskellunge to evaluate stocking success and

natural recruitment, 4) Retaining a regulation change of 10 panfish/day to prevent further reduction in

bluegill size structure, 5) Working with local residents, associations and groups to formulate fisheries

management goals, habitat protection and restoration as well as education of users and riparian residents.

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Introduction

Middle Eau Claire Lake is a 902 acre soft water drainage lake on the Eau Claire Lakes Chain in

the southwestern section of Bayfield County. The Eau Claire River runs through the chain from Upper to

Middle to Lower Eau Claire Lake. In addition, Bony Lake drains into Middle Eau Claire Lake.

Maximum depth of Middle Eau Claire Lake is 66 feet with a mean depth of 17 feet and total alkalinity of

63 mg/L. The lake has a highly developed shoreline and public access through a boat landing located at

the southeast end of the lake (Appendix Figure 1). Average summer secchi disk depth trophic state index

(TSI) value for the deep hole on Middle Eau Claire Lake was 34.8 (SD = 3.8, N = 213), for the time

period between 1987 and 2013. Average summer chlorophyll-a and total phosphorus TSI values for the

deep hole on Middle Eau Claire Lake were 43.1 (SD = 4.7, N = 39) and 48.5 (SD = 4.3, N = 41) for the

time period between 2002 and 2013. TSI is an index for evaluating trophic state or nutrient condition of

lakes. TSI values can be computed for water clarity (secchi disk measurements), chlorophyll-a, and total

phosphorus values. TSI values represent a continuum ranging from very clear, nutrient poor water (low

TSIs) to extremely productive, nutrient rich water (high TSIs). The data on Middle Eau Claire Lake

indicate the nutrient condition was mesotrophic when considering total phosphorus and chlorophyll-a TSI

indices and oligotrophic for secchi disk TSI index.

Middle Eau Claire Lake has a diverse fishery consisting of walleye Sander vitreus, muskellunge

Esox masquinongy, northern pike E. lucius, largemouth bass Micropterus salmoides, smallmouth bass M.

dolomieui, bluegill Lepomis macrochirus, pumpkinseed L. gibbosus, warmouth L. gulosus, rock bass

Ambloplites rupestris, black crappie Pomoxis nigromaculatus, yellow perch Perca flavescens, white

sucker Catostomus commersoni, yellow bullhead Ictalurus natalis, black bullhead I. melas, brown

bullhead I. nebulosus, golden redhorse Moxostoma erythrurum, logperch Percina caprodes, Iowa darter

Etheostoma exile, least darter E. microperca, brook silverside Labidesthes sicculus, bluntnose minnow

Pimephales notatus, common shiner Notropis cornutlus, mimic shiner N. volucellus, blackchin shiner N.

heterodon, and spottail shiner N. hudsonius.

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Past management of Middle Eau Claire Lake includes fishery surveys, stocking, various fishing

regulations and large woody habitat restoration projects. Walleye surveys were conducted in 1993, 1998,

2004, 2007 and 2010 utilizing Wisconsin Department of Natural Resources (WDNR) standardized treaty

protocols (Hennessey 2002). A walleye survey was also conducted in 1983 by WDNR which attempted

to calculate a population estimate using the Chapman modification of the Petersen estimator. However,

the recapture rate was low and the Schnabel method needed to be used to estimate the walleye population.

Additional walleye surveys were conducted in 1991 and 1996 using a different sampling protocol, i.e.

electrofishing to both mark and recapture walleye for a population estimate.

Middle Eau Claire Lake has a long stocking history (Table 1) and has been stocked with a number

of fish species, including walleye, muskellunge, largemouth bass and various panfish species, since at

least 1933. Only walleye were stocked from 1951 to 1965, and between 1965 and 1982 there was no

stocking due to evidence of adequate natural reproduction of all species present (Weiher 1968). Rainbow

trout were also stocked in 1985, 1988 and 1991 and discontinued thereafter due to poor returns to creel

(Scholl 1994). Walleye fry stocking began again in 1982 and alternated with fingerlings starting in 1987.

Walleye stocking in 1987 was initiated because the 1983 population estimate indicated that densities were

below the 3 adult/acre statewide management objective. Walleye stocking was discontinued after 1993

due to increased density of adults and adequate natural reproduction (Scholl 1994). In 2013 large

fingerling walleye were purchased, stocked and fin clipped by the Eau Claire Lakes Conservation Club

after the 2013 population estimate again indicated that densities were below the 3 adult/acre statewide

management objective. In 1984 muskellunge stocking began in an attempt to introduce an additional

shallow water predator to help control abundant slow growing panfish (Schram 1984). Muskellunge were

stocked on an annual basis from 1987 to 1998 with the exception of 1994 and 1995, when no muskellunge

were stocked, due to hatchery renovations in Spooner. Since 2000, muskellunge have been stocked on an

alternate year basis and since 2004 all stocked muskellunge have been fin clipped or pit tagged in an

attempt to ascertain survival and contribution rates (fin clip) and/or long term individual growth (pit tag).

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Walleye fishing regulations have changed over time in Middle Eau Claire Lake. There was no

minimum length limit for walleye until 1990 when a 15 in minimum length limit was instituted statewide.

A regulation with no length limit, but only one walleye over 14 in bag limit was instituted in 1997 when

survey data indicated that there was a high density, slow growing population which had a suspected high

natural mortality rate (Scholl 1994). The new regulation intended to focus harvest on abundant smaller

walleye and provide some measure of protection to larger walleye. Bag limits for walleye have been

adjusted annually according to tribal harvest declarations that began in 1988. Muskellunge regulations for

minimum length increased from 30 in to 32 in in 1983 and to 40 in in 1996. The panfish bag limit was

reduced from 25 to 10 in 2008 due to a 58% reduction of abundance of bluegill between 1983 and 2004.

The regulation was intended to protect the bluegill population from over exploitation by anglers. With the

exception of walleye, muskellunge and panfish, other fish species have largely been managed via

statewide length and bag limits.

Recent management has focused on muskellunge stocking, regulation changes, public outreach

and education and habitat protection/restoration. Rusty crayfish Orconectes rusticus, have been present in

Middle Eau Claire Lake since at least the 1980s, however it has not been well documented when they first

entered the lake. Rusty crayfish, from anecdotal accounts, have reduced the amount of aquatic vegetation

dramatically. In an effort to mimic habit that was once provided by the aquatic plant communities, 84 fish

cribs were installed between 1988 and 2002. Large wood, in the form of whole trees, were taken from

upland areas and placed along the shoreline in an attempt to mimic natural tree falls and increase the

abundance of wood in the littoral zone in 2009 and 2010. One hundred and thirty nine trees were installed

along the shoreline during both years combined.

Objectives of the 2013-2014 survey was to determine the status of the walleye, muskellunge,

northern pike, largemouth and smallmouth bass populations, along with sport and tribal use of these

species. More specifically, we were interested in determining population abundance, growth, size

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structure and harvest of walleye, largemouth and smallmouth bass. We also hoped to determine some

population parameters of panfish in Middle Eau Claire Lake.

Methods

Middle Eau Claire Lake was sampled in 2013-2014 following the Wisconsin Department of

Natural Resources comprehensive treaty assessment protocol (Hennessey 2002). This sampling included

spring fyke netting and electroshocking to estimate walleye, bass (both largemouth and smallmouth),

muskellunge and northern pike abundance, late June fyke netting for panfish abundance and fall

electroshocking to estimate year class strength of walleye young-of-the-year (YOY), and a creel survey

(both open water and ice fishing).

Walleye were captured for marking in the spring shortly after ice out with fyke nets. Each fish

was measured (total length; inches and tenths) and fin-clipped. Adult (mature) walleyes were defined as a

fish for which sex could be determined and fish 15 in or longer. Adult walleyes were given a lake-

specific mark. Walleyes of unknown sex less than 15 inches in length were classified as juveniles

(immature) and were marked with a different lake-specific fin clip. Marking effort was based on a goal

for total marks of 10% of the anticipated spawning population estimate. To estimate adult abundance,

walleyes were recaptured 1-2 days after netting. Because the interval between marking and recapture was

short, electrofishing of the entire shoreline was conducted to ensure equal vulnerability of marked and

unmarked walleyes to capture. All walleyes in the recapture run were measured and examined for marks.

All unmarked walleyes were given the appropriate mark so that a total population estimate could be

estimated. Population estimates were calculated with the Chapman modification of the Petersen

Estimator using the equation:

)1()1)(1(

+++

=R

CMN

where N is the population estimate, M is the total number of marked fish in the lake, C is the total number

of fish captured in the recapture sample, and R is the total number of marked fish captured. The Chapman

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Modification method is used because simple Petersen Estimates tend to overestimate population sizes

when R is relatively small (Ricker 1975). Abundance and variance were estimated for walleye that were

≥ 15 in and sexable.

Northern pike and muskellunge catch per unit effort and size structure indices (CPUE: the number

of northern pike and muskellunge caught/net lift) were calculated from the spring netting survey.

Additional fyke netting surveys targeting muskellunge were conducted in 2007 and 2008 and used to

generate a population estimate. Muskellunge collected were measured to the nearest 0.1 in and observed

for fin-clips. Abundance of muskellunge > 30 in was calculated using 2007 and 2008 as the marking and

recapture sample, respectively (Hanson 1986). Numbers in the recapture sample were adjusted for

recruitment over a 1-year period using average Wisconsin growth rates.

Largemouth and smallmouth bass encountered during fyke netting and subsequent electroshocking

runs (adult and total walleye) were marked. Bass ≥ 12.0 in were given a primary (adult) fin-clip. Bass

8.0-11.9 in were given secondary (juvenile) fin-clip for the lake. For comparison purposes catch per unit

effort and size structure indices (CPUE: the number of largemouth or smallmouth bass caught/mile of

electroshocking) were calculated from the second electroshocking survey. Panfish catch per unit effort

and size structure indices (CPUE: the number of panfish caught/net lift) were calculated from panfish

netting surveys which occurred in June of 2004, 2007, 2010 and 2013 while bluegills were actively

utilizing nesting sites. Rusty crayfish abundance was obtained during walleye fyke netting in 2004, 2007

and 2013.

Walleye age and growth were determined from dorsal spine cross sections viewed microscopically

at 100X (Margenau 1982). Age and growth of other fish species were determined by viewing acetate

scale impressions under a 30X microfilm projector. Growth rates for all species were compared to an 18

county regional mean (Northern Region) using the Fisheries Management Database (FMDB). Size

structure quality of species sampled was determined using the indices proportional (PSD) and relative

(RSD) stock densities (Anderson and Gutreuter 1983). The PSD and RSD value for a species is the

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number of fish equal to or greater than a specified length divided by the number of fish greater or equal to

stock size then the result multiplied by 100 (Appendix Table 1). Changes in population size structure

were determined using Kolmogorov-Smirnov tests. Changes in mean length were determined using a

regression model.

A random stratified roving access design was used for creel surveys (Beard et al. 1997;

Rasmussen et al. 1998). The survey was stratified by month and day-type (weekend / holiday or

weekday), and the creel clerk conducted interviews at random within these strata. The survey was

conducted on all weekends and holidays, and a randomly chosen two or three weekdays each week. Only

completed-trip interview information was used in the analysis. The clerk recorded effort, catch, harvest,

and targeted species from anglers completing their fishing trip. The clerk also measured the total length

of harvested fish and examined them for fin-clips.

Results

Total survey effort in 2013 included 48 fyke net lifts targeting spawning gamefish. In June a

second fyke-netting period targeted spawning panfish and included 12 fyke net lifts. Three

electroshocking surveys of the entire shoreline totaling 7.5 hours in spring (first and second recapture

surveys) and 3.3 hours in fall (walleye recruitment survey) were conducted.

Walleye. Adult walleye abundance (≥ 15 in and sexable fish) was 2,304 (CV = 20%; 2.6 adults/acre) in

2013. Adult walleye density is lower in the time period from 2010-2013 compared to the time period

from 1991-2007 (Figure 1). Density estimates from 1991 to 2007 averaged 5.1 fish/acre (SD = 0.7, N =

6) and 2.5 fish/acre (SD = 0.1, N = 2) in 2010 and 2013. Adult walleye density in 1983 was the third

lowest of all surveys conducted, but may reflect a gear bias (net mark/net recapture).

Walleye populations have been shifting towards larger fish since 1983 (Table 2; Figure 2). The

size structure of walleye has changed in relation to the abundance of walleye in Middle Eau Claire Lake

over time. In survey years when adult walleye abundance was greater than the average of 4.2 adults/acre

(1993–2007), the proportion of walleye between 10 and 14.9 inches captured in fyke nets was 61%. In

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survey years when the adult walleye abundance was less than the average of 4.2 adults/acre (1983, 2010

and 2013), the proportion of walleye between 10 and 14.9 inches captured in fyke nets was 25%.

Conversely, the proportion of walleye 15 inches and greater captured in fyke net was 19% for years with

higher than average walleye abundance (1993-2007) and 37% for years with lower than average walleye

abundance (1983, 2010 and 2013). The increase in mean length was significant (t-Stat = 6.5, P = 0.003;

Table 3). Proportional stock density (PSD) values ranged widely from 16 (1993) to 91(2013), in contrast

to RSD-20 values which ranged narrowly from 2 (2013) to 4 (2004), indicating the proportion of walleye

over 20 in has been low for all survey years (Figure 3).

Age of adult walleye sampled during the 2013 survey ranged from III to XII. Male and female

walleye first reached maturity at III and IV, respectively. Age VI walleye accounted for 21% of the adult

stock. Age distribution data from 1993, 1998, 2004, 2007, 2010 and 2013 indicate consistent naturally

reproduced year classes (Figure 4). Growth rates for both sexes were dimorphic with males reaching 15

in between ages IV and V and females prior to age IV in the 2013 survey. Growth rates in 1993, 1998,

2004, 2007 and 2010 were predominately below Northern District averages, especially for walleye age

VII and older. In contrast, growth rates in 2013 were above regional averages for ages II to V and below

regional growth rates after age V (Figure 5).

Relative abundance of young-of-year (YOY) walleye in Middle Eau Claire Lake in 2013 was 24.8

fish/mile (57.9 fish/hour) for fall electrofishing. The average walleye YOY/mile was 88.2 (SD = 108.1, N

= 28) for surveys completed from 1985 to 2013 by both WDNR and GLIFWC. However, fingerling

relative abundance has been highly variable from 1985 to 2013 with a range of 3.9 fish/mile to 525.5

fish/mile (6.9 fish/hour to 986.8 fish/hour; Figure 6). Mean relative abundance of YOY walleye for

naturally reproducing walleye lakes surveyed by WDNR in Bayfield and Douglas Counties from 1991 to

2013 was 24.6 fish/mile (SD = 51.3, N = 96).

Largemouth and Smallmouth Bass. In 2013, largemouth bass represented 66% and smallmouth bass 34%

of the total number of bass surveyed (N = 162). Largemouth and smallmouth bass abundance has

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increased since 1993. However, largemouth bass abundance surpassed abundance of smallmouth bass in

2013 and was 9.7 and 5.0 fish/mile for largemouth and smallmouth bass, respectively (Figure 7).

Largemouth bass PSD and RSD-15 values were 58 and 15 and the longest fish was 20.2 inches for the

2013 survey. Smallmouth bass PSD and RSD-14 values were 65 and 31 and the longest fish was 19.7

inches for the 2013 survey.

Muskellunge and Northern Pike. Relative abundance (the number of fish caught with each fyke net lift)

of muskellunge was 0.1 fish/net lift in 2013. Muskellunge relative abundance averaged 0.36 (SD = 0.18)

fish/net lift from 1993 to 2010. There was not an adequate number of muskellunge marked to perform a

population estimate, with the exception of 2007. Muskellunge abundance from the 2007 population

estimate was 0.13 (CV = 18%, N = 115) fish/acre for fish ≥ 30 inches and confirmed that Middle Eau

Claire has sustained a low density muskellunge population for all survey years. Changes in mean length

of muskellunge were not significant (t-Stat = 1.0, P = 0.373; Table 4). RSD-34 and RSD-40 indicated a

quality size structure over most survey years (Table 4). The largest muskellunge caught during the 2013

fyke netting survey was 42.8 inches.

Relative abundance of northern pike was 1.8 fish/net lift in the 2013 survey. Northern pike relative

abundance averaged 1.24 (SD = 0.32) fish/net lift from 1993 to 2010. Similar to muskellunge, there was

not an adequate number of northern pike marked to estimate abundance; however, the density of northern

pike appeared to be low in all years. Changes in northern pike mean length were not significant, but have

increased over time (t-Stat = 2.4, P = 0.076; Table 5). PSD and RSD-30 for spring fyke net samples also

indicate an increasing size structure (Table 5). The largest northern pike caught during the 2013 fyke

netting survey was 40.0 inches.

Panfish. Bluegills were the most abundant panfish species (N = 1,404) sampled in Middle Eau Claire

Lake during the panfish fyke netting survey of 2013. Relative abundance of bluegill captured in panfish

survey fyke nets decreased then increased from 35.8 to 27.9 to 25.7 to 117.0 fish/net lift during 2004,

2007, 2010 and 2013, respectively. Length frequency of bluegill captured during panfish netting surveys

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suggests a significant shift in size structure between all years, with fish from 2.5 to 3.5 inches in length

increasing in 2010 and 2013 (Table 6: Figure 8). PSD for bluegill average was 68 (SD = 19.0) and RSD-

8 average was 8 (SD = 1.9) for all panfish netting survey years, indicating a quality size structure over

time. Age of bluegill sampled during the 2013 survey ranged from II to X. Growth rates in 2004, 2010

and 2013 were predominately below Northern District averages, for ages II to V and above regional

average for bluegill age VI and older (Figure 9).

Rock bass were the second most abundant panfish species (N = 74) sampled in Middle Eau Claire

Lake during the panfish fyke netting survey of 2013. Relative abundance of rock bass captured decreased

from 21.6 to 9.9 to 6.7 to 6.2 fish/net lift in 2004, 2001, 2010 and 2013 respectively. Mean total length of

rock bass was 7.4 inches (SD = 1.6, N = 74) in 2013. Warmouth were the third most abundant panfish

species (N = 65) sampled during panfish netting in 2013. In contrast, only two warmouth were sampled

during historic panfish netting. Pumpkinseed were the fourth most abundant panfish species (N = 60)

sampled during panfish netting in 2013. Pumpkinseed relative abundance decreased slightly from 0.36 to

0.21 fish/net lift from 2004 to 2007 then increased to 1.8 and 5.0 fish/net lift from 2010 to 2013. Twenty

eight black crappie were sampled during panfish netting in 2013, mean total length was 10.0 (SD = 1.4)

inches. The largest sample of yellow perch was obtained during the walleye fyke netting period (N =

469) in 2013. Total abundance and mean total length of yellow perch was 9.8 fish/net lift and 4.7 inches

(SD = 0.6) in 2013. In comparison, total abundance during the walleye fyke netting periods was 0.1, 0,

0.9 and 0.4 in 1998, 2004, 2007 and 2010, respectively.

Rusty Crayfish. Rusty crayfish abundance was 30.5, 53.6 and 2.3 crayfish/net lift in 2004, 2007 and

2013.

Sport and Tribal Fishery. Anglers fished an estimated 14,398 hours (16.0 hrs/acre) during the 2013-2014

(hereafter referred to as 2013) season in Middle Eau Claire Lake, which is below the average of 25.4

hrs/acre (SD = 14.4, N = 58) for Bayfield and Douglas County walleye lakes (WDNR unpublished data,

Brule field office) and below the Northern Wisconsin Region (21 counties) average of 32.7 hrs/acre (SD =

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23.5, N = 500) from 1990 to 2012. Fishing pressure declined on Middle Eau Claire Lake in 2013 when

compared to historic surveys. Fishing pressure (hrs/acre) was 22.4, 22.9, 21.9, 21.7 and 22.4 during 1993,

1998, 2004, 2007 and 2010, respectively. Open water anglers accounted for 94% of all fishing effort in

2013. Directed effort for gamefish ( i.e. effort targeted toward a specific fish) was highest for walleye

(17%; Table 2). The most sought after panfish species was bluegill, with 24% of the directed effort (Table

2).

Walleye were the second most heavily exploited gamefish, next to northern pike, in Middle Eau

Claire Lake. An estimated 566 walleye were caught in the open water and ice season of 2013 of which

61% (347) were harvested. The open water season accounted for 80% of the total walleye harvest, which

was in the same range for values from 1993 (93%), 1998 (84%), 2004 (90%), 2007 (46%) and 2010

(95%). Average length of angler harvested walleye was 15.6 inches (SD = 2.7, N = 64). Projected total

harvest by anglers was lowest in 2013 when compared to other creel surveys, 1993 (365), 1998 (1,511),

2004 (1,299), 2007 (1,138) and 2010 (1,227) (Figure 10). Angler exploitation, calculated by dividing the

estimated number of marked walleye harvested by the total number of marked walleye, was 4.6% in 2013.

Tribal harvest accounted for 241 walleye in 2013. Tribal harvest represented 41% of the

combined total harvest (sport angling plus tribal spearing) and tribal exploitation of the adult walleye

population was 11.1%. Walleye harvested ranged from 11.8 to 24.5 inches. The mean length of tribally

harvested walleye was 16.6 inches (SD = 2.0, N = 241) and 15% were < 15 inches. Male and female

walleye represented 83% and 9% of the total tribal harvest, respectively. The remaining 8% were walleye

of unknown sex.

Total walleye exploitation (sport and tribal) was 7.3%, 21.4%, 24.4%, 13.7%, 23.0%, and 15.70%

during 1993, 1998, 2004, 2007, 2010 and 2013, respectively. Exploitation levels below 35% are

generally thought to be sustainable and are the exploitation levels that are used to determine total

allowable catch for the combined fishery of angler and tribal harvest for walleye in the state of Wisconsin.

Exploitation levels found on Middle Eau Claire Lake have remained below 35%.

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The second most sought after gamefish species by anglers was muskellunge with 14.4% of the

directed effort which has remained consistent across survey years (Table 7). In the open water season of

2004 an estimated 32 muskellunge were caught, none of which were harvested. Tribal harvest accounted

for 1 muskellunge in 2013.

Northern pike were the most exploited (harvest = 348) gamefish in 2013 on Middle Eau Claire

Lake and had the fourth highest directed effort (13.1%) of gamefish. Estimated catch of northern pike

was 3,246 in 2013. Directed effort for northern pike remained consistent across survey years (Table 7).

Northern pike estimated catch and harvest has fluctuated over time (Figure 10). Mean length of harvested

northern pike remained similar (Table 8).

Smallmouth bass were the third most sought after gamefish in the open water season of 2013 on

Middle Eau Claire Lake with 13.5% of directed effort. The highest directed effort toward smallmouth

bass occurred in 2004 (33%). An estimated 2,044 smallmouth were caught, 48 of which were harvested

in 2013. Estimated catch of smallmouth bass has increased 20-fold since 1993 (Figure 10). Estimated

harvest of smallmouth bass was under 65 fish/year for all survey periods (Figure 10).

Largemouth bass were the least sought after gamefish by anglers in Middle Eau Claire Lake in

2013 with 10.3% of directed effort, but had the highest directed effort for largemouth bass when

comparing all creel survey years. Estimated catch of largemouth bass was 1,499 of which 31 fish were

harvested in 2013. Estimated catch of largemouth bass has increased over time (Figure 10). Estimated

harvest of largemouth bass was under 35 fish/year for all survey periods (Figure 10).

Anglers pursuing panfish fished an estimated 5,853 hours and accounted for 32.3% of the total

directed angling effort in 2013. Bluegill was the most sought after panfish species by anglers in 2013

with 23.5% of the directed effort. Angler estimated catch and harvest of bluegill declined prior to, then

increased after the 10 fish/day bag limit was instituted (Figure 10). Mean total length of harvested

bluegill remained consistent over all survey periods (Table 8). Black crappies were the second most

sought after panfish species (5.8%) by anglers in 2013 and was the highest directed effort in all creel

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survey years for that species. Estimated angler catch and harvest has historically been low, with a recent

increase in 2013 (Figure 11). Mean total length of angler harvested black crappie in 2013 was 10.3 (SD =

1.0, N = 134) in. Directed effort for yellow perch was 0.3% in 2013 and was the fourth most sought after

panfish by anglers. Estimate catch and harvest for yellow perch was inversely related with bluegill catch

and harvest (Figure 11).

Discussion

Middle Eau Claire Lake has supported, and continues to support a diverse fish community and

popular sport fisheries. With the exception of muskellunge, natural reproduction supports all species.

Harvest management aimed at maintaining self-sustaining stocks has been largely successful. The recent

decline in walleye abundance could be related to shifting habitat types but may also be a reflection of

declining walleye abundance throughout the northwest section of the state, the causes of which are yet

unknown.

Walleye abundance has declined by half when comparing average density from 1991 to

2007{5.1 fish/acre (SD = 0.7, N = 6)} and 2010 to 2013 {2.5 fish/acre (SD = 0.1, N = 2)} and is now

below the state walleye management objective of 3.0 adults/acre. Walleye abundance on Middle Eau

Claire Lake was also below the Bayfield and Douglas County naturally reproducing lakes average of 3.0

adults/acre (SD = 2.0, N = 66) from 1991 to 2013. Interestingly, the walleye abundance decline on

Middle Eau Claire Lake was similar to the decline of Bayfield and Douglas Counties naturally

reproducing walleye lakes. Walleye abundance on naturally reproducing walleye lakes in Bayfield and

Douglas Counties declined from 3.7 adults/acre (SD = 2.2, N = 33) from 1991 to 2001 to 2.3 adults/acre

(SD = 1.3, N = 33) from 2002 to 2013. A change in length indices and age composition suggests a shift to

larger, older fish although recruitment was still present on Middle Eau Claire Lake. Factors contributing

to the decline in adult walleye abundance may be related to declining rusty crayfish abundance resulting

in habitat changes, sporadic natural recruitment, changes in weather patterns, increases in largemouth bass

(or other centrarchid) abundance, or unknown variables that are yet to be identified.

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Rusty crayfish, an exotic species, appears to have had an effect on fishery composition since they

were first found in the 1980s by dramatically reducing the amount of aquatic vegetation. The reduction of

littoral zone habitat by rusty crayfish has been reported in both natural and laboratory conditions (Wilson

et al. 2004; Lodge and Lorman 1987). Since 2007, rusty crayfish populations have declined which led to

increasing abundance of aquatic vegetation and a corresponding effect on fishery composition. In 2013,

rusty crayfish abundance declined 92% and 96% when compared to 2004 and 2007. Optimal vegetative

cover (% of the bottom covered with aquatic vegetation) for adult walleye is believed to be in the order of

25-45% (McMahon et al. 1984). Without vegetative cover data from Middle Eau Claire Lake it is

difficult to surmise effects of changes to aquatic plant abundance by rusty crayfish.

Walleye recruitment remained consistent for Middle Eau Claire Lake. Relative abundance of

YOY walleye from fall electrofishing surveys has varied, however, when comparing 1991 to 2007 (period

with high adult walleye abundance) with 2008 to 2013 (period with low adult walleye abundance) mean

relative abundance declined from 110.1 (SD = 130.9, N = 17) to 44.5 (SD = 13.8, N = 6) fish/mile on

Middle Eau Claire Lake. The largest difference between the two periods was that from 1991 to 2007

there were six years when the YOY walleye abundance exceeded 100 fish/mile; from 2008 to 2013 no

surveys exceeded 100 fish/mile. Even though there appears to have been a decline in the relative

abundance of YOY walleye in Middle Eau Claire Lake for the period from 2008 to 2013, YOY walleye

abundance during that period was still 34% higher than the regional average for naturally reproducing

walleye lakes from 1990 to 2013. Due to continued adequate natural reproduction walleye, stocking is

not recommended unless future fall electrofishing surveys decline below 10 young of the year walleye per

mile for three consecutive years.

Climate change has been identified as a potential cause in the shift of cold, cool and warmwater

species to more northern areas where they had been uncommon in the past. Shuter et al. (2002), Jackson

and Mandrak (2002), Chu et al. (2005) and Sharma et al. (2007) predicted increases in water temperature

in response to climate change will have large implications for aquatic ecosystems in Canada, such as

17

altering thermal habitat and potential range expansion of fish species. They surmised that warmwater fish

species may have access to additional favorable thermal habitat under increased surface-water

temperatures, thereby shifting the northern limit of the distribution of the species further north and

potentially negatively impacting native fish communities. Walleye are considered a coolwater fish

species and could be susceptible to decreasing coolwater habitat as a result of climate change (Eaton and

Scheller 1996).

Negative species interactions have been identified between walleye and largemouth bass

populations. Nate et al. (2003) indexed relative abundance of five gamefish species on the basis of

general angler catch rates from creel surveys on 60 lakes in northern Wisconsin during 1990-2001.

Analysis revealed higher angler catch rates (presumably greater abundance) of largemouth bass and

northern pike on 30 lakes with “stocked” walleye populations (demonstrably lower walleye density), and

higher angler catch rates for walleye and muskellunge on 30 lakes with “self-sustaining” walleye

populations where angler catch rates (and presumed abundance) of largemouth bass were lowest. In a

more recent analysis of 20 northern Wisconsin lakes with at least 50% natural recruitment of walleye,

Fayram et al. (2005) reported a significantly negative relationship between adult walleye density and

multi-season electrofishing capture rate of largemouth bass. They concluded that management of both

species in the same water body may be difficult. Largemouth bass populations have increased on Middle

Eau Claire Lake as walleye populations have decreased. Whether the increase of largemouth bass is the

result of filling a predatory void left by decreasing walleye populations, largemouth bass population

taking advantage of more conducive habitat, spawning conditions, or directly preying on juvenile walleye

is unknown. Studies exploring these relationships and possible impacts of several different management

strategies are underway in the northern district.

Angler and tribal walleye exploitation are likely not the cause of decreased walleye abundance on

Middle Eau Claire Lake. Total walleye exploitation (sport and tribal harvest) was 15% in 2013 and has

averaged 18% (SD = 6.6, N = 6) from creel surveys conducted between 1993 and 2013. The maximum

18

sustainable exploitation rate derived to set harvest quotas of the combined tribal and sport walleye fishery

in the ceded territory of northern Wisconsin is 35% (Hansen et al. 1991), exploitation rates below 35% are

thought to be sustainable.

Results from the 2013 survey suggest that the objectives of the regulation change for walleye that

included no minimum length limit but only one fish over 14 in were accomplished initially by increasing

harvest and improving size structure. Harvest of walleye increased from the 1993 survey and was a result

of anglers' willingness to harvest walleye 15 in and less. Forty four percent of walleye harvested by

anglers in 2004 were less than 15 in and total harvest increased by over 250% from 1993. In addition,

harvest of walleye 15 in and greater increased nearly 150% from 1993 to 2004. Walleye abundance

declined by 60% from 2007 to 2010. Fifty six percent of walleye harvested by anglers in 2013 were less

than 15 in, however, total harvest decreased by 73% from 2004 to 2013. Historic slow growth of walleye

was likely density dependent in Middle Eau Claire Lake which has also been identified by Sass et al.

(2004) in other high density northern Wisconsin walleye lakes. As walleye abundance has declined on

Middle Eau Claire Lake growth rates have increased. Faster growth could increase the effectiveness of a

14 to 18 in protected slot length regulation by improving size structure of the walleye population. Harvest

of walleye would also likely decline under a 14 to 18 in protected slot length limit, but would not be

expected to increase abundance, since exploitation had been below 20% as the population declined. For

example, if the regulation had been in place in 2013, 86% of walleye ≥10 inches would have been

protected from harvest and estimated angler harvest would have been reduced by 56%, resulting in an

estimated harvest of 154 walleye.

Consideration of management geared toward a larger size structure and reduced harvest for

walleye on Middle Eau Claire Lake should also be considered in a social context. Historically, Middle

Eau Claire Lake was a lake that anglers frequented for an opportunity to harvest walleye, with declining

walleye populations walleye harvest opportunities have declined. More restrictive walleye harvest

regulations are planned for implementation on Upper and Lower Eau Claire Lakes beginning in 2016, if

19

Middle Eau Claire also had a more restrictive harvest regulation consumption opportunities would be

further limited in the area. Angler preferences for Middle Eau Claire Lake are unknown and would be

helpful in discerning whether a more restrictive walleye regulation would be palatable.

As mentioned previously, largemouth and smallmouth bass abundance has increased in Middle

Eau Claire Lake from 1993 to 2013. However, largemouth bass have increased in abundance by 83%

from 2010 to 2013. The 2013 largemouth bass abundance of 9.7 fish/mile was similar to the average

abundance of largemouth bass (9.9 fish/mile, SD = 10.7, N = 38) in Bayfield and Douglas County walleye

lakes from 2002 to 2013. However, largemouth bass abundance has been increasing for Bayfield and

Douglas County walleye lakes since 1988 and this trend can also be seen on Middle Eau Claire Lake. The

increased abundance of largemouth bass represents a harvest opportunity for anglers. Starting in 2014 the

early catch and release only season for largemouth bass will end, making it legal for anglers to harvest

largemouth bass during this time period. To provide additional harvest opportunity for anglers,

largemouth bass regulations should be changed from the current minimum length limit of 14 in with a bag

limit of 5 fish per day to no minimum length limit and a bag limit of 5 fish per day. Even though

smallmouth bass abundances have also increased they remain relatively low and have developed an

excellent size structure that has provided a popular sport fishery. To protect this size structure we

recommend changing the current regulation for smallmouth bass of a 14 in length limit and a bag limit of

5 fish per day to a 20 in length limit with a bag limit of 1 fish per day. Splitting regulatory management

for largemouth and smallmouth bass would provide harvest opportunity to a rapidly expanding

largemouth bass population while protecting the excellent size structure of the smallmouth bass

populations.

Muskellunge relative abundance was low in 2013. Only 6 muskellunge were captured in fyke

nets, of which 1 was less than 30 in. While a muskellunge sport fishery exists, the low abundance does

cause some concern regarding survival of stocked fingerlings. Typically, low post-stocking survival is

associated with predation and availability of prey items (Margenau 1992). Interestingly, northern pike, a

20

prominent predator in many northern Wisconsin lakes capable of consuming large fingerling muskellunge

(10-12 in), were in low abundance. Middle Eau Claire Lake had 11,963 muskellunge stocked from 1988

to 2013 of those 4,854 or 41% from 1996 to 2002 were not fin clipped prior to release. Due to

muskellunge not being fin clipped during this period it is difficult to estimate contribution of the stocked

fish to the adult population. However, the percentage of hatchery clips found using all survey types for

muskellunge was 17%, 16% and 29% in 2007, 2010 and 2013. The assumption could be made that

stocking of muskellunge may be contributing from 17% to 29% in any given year and that these

percentages are likely low due to the presence of stocked muskellunge that were not fin clipped and

therefore not identified as being stocked. The question of contribution from natural reproduction remains

unanswered but may likely be made easier to evaluate as stocked muskellunge continue to be marked in

the future.

Northern pike relative abundance and average length has remained similar since 1993. Angler

catch and harvest of northern pike reflected the population, i.e., lower numbers but larger size, a similar

association found in other northern Wisconsin lakes (Margenau et al. 2003). Northern pike were the most

heavily exploited gamefish by anglers in 2013 and have replaced walleye in that role, although northern

pike were the 4th most sought after fish by anglers. Northern pike represent an important component of

the sport fishery and add to the lakes angling diversity along with offering some potential for a trophy

fish.

The panfish community was targeted in surveys from 2004, 2007, 2010 and 2013. Bluegill

relative abundance from 2013 has increased by 69% since 2004. The bag limit for panfish was reduced

from 25 fish per day to 10 fish per day in 2008. Pre-regulation change (2004 and 2007) average

abundance for bluegill was 31.8 fish/net lift, post regulation change (2010 and 2013) average abundance

for bluegill increased to 71.4 fish/net lift. The increase in abundance and decrease in size structure from

pre to post-regulation change can be accounted for in the increased number of bluegill in the 2 to 4 in

length range. The increase of small bluegill could be due to reduced predator abundance or increased

21

aquatic plant abundance with the effect of reducing predation. Growth rates of bluegill have declined

since 2004 and may be the result of density dependent growth. Angler estimated catch of bluegill in 2013

was the highest recorded from creels from 1993 to 2013 and estimated harvest was the second highest in

2013 with the next highest harvest having occurred in 1993 (Figure 10). In contrast, yellow perch

estimated catch and harvest by anglers was highest for all panfish species in the 2004 creel survey.

Angler directed effort for yellow perch has decreased in comparison to the 2004 creel survey. Taken

together with the decrease in walleye and yellow perch abundance and the increase in largemouth bass

and bluegill abundance these changes could be an indication of a switch from a fishery dominated by

pelagic species to one dominated by littoral species.

Summary and Management Recommendations

1. Walleye abundance in Middle Eau Claire Lake in 2013 was below the regional average and

did not meet statewide management objectives. Exploitation of walleye was low in 2013. Although the

fishery still supports good natural reproduction and recruitment, abundance has declined. The current

regulation of no minimum length and only one fish over 14 in has met the objective of increasing harvest

opportunity and increasing length frequency of the walleye population. Considering a more restrictive

regulation such as no minimum length limit and a no keep slot of 14 to 18 in to further improve size

structure should take into consideration conservative regulation changes that are expected to go into effect

on Upper and Lower Eau Claire Lakes in 2016. A more conservative walleye regulation could be

expected to decrease angler harvest but not necessarily to increase walleye abundance due to angler

exploitation likely not being a cause for walleye abundance declines on Middle Eau Claire Lake. Angler

preference data should be collected during the next creel survey scheduled for 2016. The analysis of

angler preferences will help inform the decision on whether or not to implement more restrictive

regulations for walleye on Middle Eau Claire Lake. Due to continued adequate natural reproduction,

walleye stocking is not recommended unless future fall electrofishing surveys decline below 10 young of

the year walleye per mile for three consecutive years.

22

2. Largemouth bass have increased in abundance in Middle Eau Claire Lake since 2010 and

prior survey years. Largemouth bass now represent a harvest opportunity for anglers and as such a

regulation change from a 14 in minimum length limit and a 5 fish/day bag limit to a no minimum length

limit 5 fish/day bag limit should be implemented. Smallmouth bass abundance has increased but not to

the degree of largemouth bass and remain low in abundance. Smallmouth size structure is excellent and

to preserve that a regulation change from a 14 in minimum length limit and a 5 fish/day bag limit to a 20

in minimum length limit with a 1 fish/day bag limit should be implemented.

3. Muskellunge abundance is low in Middle Eau Claire Lake, yet were the second most

sought after gamefish species by anglers in 2013. Stocking should continue for muskellunge on an

alternate year basis at the rate of 0.5 fish/acre. Stocked muskellunge should be marked with a fin-clip to

evaluate stocking success and natural recruitment in the future. Northern pike abundance was also low

but still provides the highest angler harvest among gamefish and an important component of the sport

fishery.

4. Bluegill relative abundance has increased and length frequency and growth have decreased

over time in Middle Eau Claire Lake. Littoral zone aquatic plant increase, decrease of walleye abundance

and potential effects of the 10 fish/day bag limit are likely factors of this increase. We recommend

retaining the 10 fish/day bag limit for panfish with the intent of preventing recruitment overharvest by

anglers and further decline of the size structure.

5. Changes in walleye and largemouth bass abundance on Middle Eau Claire Lake are

consistent with changes that have occurred on walleye lakes in Bayfield and Douglas Counties since

1988. The reasons for these changes remain largely unknown. Several studies probing the relation of

these changes are underway and Upper and Lower Eau Claire Lakes have been included in one study.

These studies will help test whether changing angling regulations for walleye and largemouth bass as well

as stocking large fingerling walleye can be effective in switching these lakes back to walleye as the

23

dominant predator. Findings from these studies will be used to direct fisheries management on walleye

lakes across the northern district.

6. The last recommendation is to work with local residents, the Middle Eau Claire Lake

Association, the Eau Claire Lakes Conservation Club and the WDNR lake grants program to create and

adopt a lake management plan and aquatic plant management plan including: 1) develop strategies for

protecting and restoring sensitive aquatic and shoreline habitats by utilizing critical habitat designation

recommendations, 2) continue exotic species survey and control programs targeting satellite infestations,

3) continue educational and participation forum for environmentally sensitive shoreline living, 4) continue

water quality monitoring through the citizen lake monitoring program. No amount of regulation or

stocking practices will change the need for healthy aquatic environments. Although water quality remains

high, habitat loss, declining shoreline aesthetics, and exotic introductions are warning signs of cultural

disturbances that are degrading ecosystem health. Currently, rusty crayfish are in decline which has likely

had the effect of higher aquatic plant abundance in the littoral zone and curly leaf pondweed which is also

an exotic species has been identified in Middle Eau Claire Lake. Attempts to prevent the spread of curly

leaf pondweed and the introduction of Eurasian watermilfoil from nearby sources are worthy objectives in

preserving the ecosystem as a whole. Shoreline restoration projects in areas that are currently lacking

buffers should be explored. Preventing the spread of exotics and enhancing habitat through restoration

projects, as well as preserving the existing habitat will be far more beneficial than losing what is currently

present and relying on stocking and artificial habitat improvements to maintain the fishery and ecosystem

as a whole

24

Acknowledgements

I would like to thank Lee, Sue, and Amy Wiesner and O. K. Hedlund who were volunteers for the

Self-Help Lake Monitoring Program from 1987 to 2013, and gathered the water quality data presented in

this report. Thanks to the Eau Claire Lakes Conservation Club and Property Owners Association who

assisted with volunteer hours and funding to implement the fish sticks projects completed on Middle Eau

Claire Lake. I would also like to thank the biologists and technicians of the Wisconsin Department of

Natural Resources who assisted with field collection of data, especially Cris Sand, Marty Kangas, Paul

Riordan and Bryce Ottman. The WDNR treaty assessment unit, especially Jamison Wendel, Scott

Plaster, Todd Brecka and Jill Sunderland for data collection and entry and creel survey data collection,

data entry and completion of the creel survey report. With special thanks to Terry Margenau who

provided a critical review of the manuscript.

25

References

Anderson, R. O., and S. J. Gutreuter. 1983. Length, weight, and associated structural indices. Pages 283-300 in L. Nielson and D. Johnson, editors. Fisheries Techniques. American Fisheries Society, Bethesda, Maryland. Beard, T. D., Jr., S. W. Hewett, Q. Yang, R. M. King, and S. J. Gilbert. 1997. Prediction of angler catch rates based on walleye population density. North American Journal of Fisheries Management 17: 621-627. Chu, C., N. F. Mandrak and C. K. Minns. 2005. Potential impacts of climate change on the distributions of several common and rare freshwater fishes in Canada. Diversity and Distributions, 11, 299- 310. Eaton, J. G. and R. M. Scheller. 1996. Effects of climate warming on fish thermal habitat in streams of the United States. Limnol. Oceanogr, 4l(5), 1109-1115. Fayram, A. H., M. J. Hansen and T. J. Ehlinger. 2005. Interactions between walleyes and four fish species with implications for walleye stocking. North American Journal of Fisheries Management 25:1321-1330, 2005. Hanson, D. A. 1986. Population characteristics and angler use of muskellunge in eight northern Wisconsin lakes. Pages 238 -248 in G.E. Hall, editor. Managing muskies. American Fisheries Society Special Publication 15, Bethesda, Maryland. Hansen, M. J., M. D. Staggs, and M. H. Hoff. 1991. Derivation of safety factors for setting harvest quotas on adult walleyes from past estimates of abundance. Transactions of the American Fisheries Society Volume 120: Pages 620-628, 1991. Hennessy, J. 2002. Ceded territory fishery assessment report. Wisconsin Department of Natural Resources. Administrative Report 55, Madison. Jackson, D. A. and N. E. Mandrak. 2002. Changing fish biodiversity: predicting the loss of cyprinid biodiversity due to global climate change. pp. 89-98 in: N.A. McGinn (ed.), Fisheries in a Changing Climate. American Fisheries Society, Symposium 32, Bethesda, Maryland. Lodge, D.M. and J.G. Lorman. 1987. Reductions in submersed macrophyte biomass and species richness by the crayfish Oronectes rusticus. Canadian Journal of Fisheries and Aquatic Sciences 44:591- 597. Margenau, T. L. 1982. Modified procedure for aging walleye by dorsal spine sections. Progressive Fish-Culturist 44:204. Margenau, T. L. 1992. Survival and cost-effectiveness of stocked fall fingerling and spring yearling muskellunge in Wisconsin. North American Journal of Fisheries Management 12:484-493. McMahon, T. E., J. W. Terrell, and P. C. Nelson. 1984. Habitat suitability information: Walleye. Report FWS/OBS-82/10.56, U.S. Fish and Wildlife Service. 43 p.

26

Nate, N.A., M.A. Bozek, M.J. Hansen, C.W. Ramm, M.T. Bremigan, and S.W. Hewett. 2003. Predicting the occurrence and success of walleye populations from physical and biological features of northern Wisconsin lakes. North American Journal of Fisheries Management 23:1207-1214. Rasmussen, P. W., M. D. Staggs, T. D. Beard, Jr., and S. P. Newman. 1998. Bias and confidence interval coverage of creel survey estimators evaluated by simulation. Transactions of the American Fisheries Society 127: 460-480. Ricker, W. E. 1975. Computation and interpretation of biological statistics of fish populations. Bulletin of the Fisheries Research Board of Canada 191. Department of the Environment, Fisheries, and Marine Science, Ottawa. 382 p. Scholl, D. 1994. 1993 Fishery Survey Summary, Middle Eau Claire Lake, Bayfield County. Brule – Office File. Schram, S. 1984. Lake Survey Summary – Middle Eau Claire Lake, Bayfield County. Brule Office File. Sharma, S., D. A. Jackson, C. K. Minns, and B. J. Shuter. 2007. Will northern fish populations be in hot water because of climate change? Global Change Biology Volume 13 Issue 10, Pages 2052 – 2064. Shuter, B.J., C.K. Minns and N. Lester. 2002. Climate change, freshwater fish and fisheries: Case studies from Ontario and their use in assessing potential impacts. pp. 77-88 in: N.A. McGinn (ed.), Fisheries in a Changing Climate. American Fisheries Society, Symposium 32, Bethesda, Maryland. Weiher, W. 1968. Lake Survey of Middle Eau Claire Lake, Bayfield County. Brule – Office File. Wison, Karen A., John Magnunson, David M. Lodge, Anna M. Hill, Timothy K. Kratz, William L. Perry, and Theodore V. Willis. 2004. A long-term rusty crayfish (Orconectes rusticus) invasion:dispersal patterns and community change in a north temperate lake. Canadian Journal of Fisheries and Aquatic Sciences 61:2255-2266.

27

Table 1. Fish stocking history of Middle Eau Claire Lake, Bayfield County, Wisconsin.

Year Species Number Stocked

Age/Size

1933 Walleye 283,360 Fry1936 Bass 600 Unknown

Bluegill 160 UnknownMuskellunge 12,650 UnknownWalleye 793,800 Fry

1937 Muskellunge 18,180 FryBlack Crappie 850 Adult

1938 Largemouth Bass 122 FingerlingMuskellunge 25,000 FryPerch 520 FingerlingBluegill 7,584 Fingerling

1939 Largemouth Bass 500 FingerlingLargemouth Bass 272 YearlingMuskellunge 38,760 FryWalleye 2,100,000 Fry

1940 Muskellunge 70,000 FryWalleye 4,000,000 Fry

1941 Largemouth Bass 2,000 FingerlingMuskellunge 1,035 FingerlingMuskellunge 13,000 FryWalleye 552 FingerlingWalleye 4,100,000 Fry

1942 Walleye 1,900,000 FryWalleye 2,650 FingerlingMuskellunge 98,000 FryMuskellunge 1,200 Fingerling

1943 Walleye 950,000 FryWalleye 6,000 FingerlingMuskellunge 98,000 FryMuskellunge 1,200 FingerlingLargemouth Bass 1,185 Fingerling

1944 Walleye 760,000 FryWalleye 2,000 FingerlingMuskellunge 29,000 FryMuskellunge 800 FingerlingLargemouth Bass 2,000 Fingerling

1945 Walleye 1,450,000 FryWalleye 6,775 FingerlingMuskellunge 33,750 FryMuskellunge 400 FingerlingLargemouth Bass 4,500 Fingerling

1946 Walleye 1,190,000 FryWalleye 4,000 FingerlingMuskellunge 963 FingerlingLargemouth Bass 2,375 Fingerling

1947 Muskellunge 1,700 FingerlingLargemouth Bass 2,200 Fingerling

1948 Walleye 3,200,000 FryWalleye 7,900 FingerlingLargemouth Bass 7,900 Fingerling

28

Table 1 (continued). Fish stocking history of Middle Eau Claire Lake, Bayfield County, Wisconsin. Year Species Number

Stocked Age/Size

1949 Walleye 2,600 Fry Walleye 3,050 Fingerling Largemouth Bass 5,602 Fingerling

1950 Walleye 9,349 Fingerling Largemouth Bass 6,650 Fingerling

1951 Walleye 8,815 Fingerling 1952 Walleye 11,800 Fingerling 1953 Walleye 7,400 Fingerling 1954 Walleye 11,720 Fingerling 1955 Walleye 3,700 Fingerling 1956 Walleye 7,400 Fingerling 1957 Walleye 7,400 Fingerling 1958 Walleye 2,466 Fingerling 1959 Walleye 22,200 Fingerling 1962 Walleye 3,768 Fingerling 1965 Walleye 9,135 Fingerling 1982 Walleye 2,000,000 Fry 1984 Muskellunge 900 Fingerling 1985 Rainbow Trout 2700 Yearling

Rainbow Trout 33 Adult 1987 Muskellunge 450 Fingerling

Walleye 39,412 Fingerling 1988 Rainbow Trout 2,700 Yearling

Muskellunge 1,000 Fingerling 1989 Walleye 46,044 Fingerling

Muskellunge 900 Fingerling 1990 Muskellunge 450 Fingerling 1991 Walleye 454,000 Fry

Muskellunge 900 Fingerling Rainbow Trout 2,700 Yearling

1992 Walleye 40,000 Fry Walleye 22,550 Fingerling Muskellunge 900 Fingerling

1993 Walleye 45,675 Fingerling Muskellunge 900 Fingerling

1996 Muskellunge 900 Fingerling 1997 Muskellunge 450 Fingerling 1998 Muskellunge 800 Fingerling 2000 Muskellunge 900 Fingerling 2002 Muskellunge 1,804 Fingerling 2004 Muskellunge 451 Fingerling 2006 Muskellunge 255 Fingerling

Walleye 300,000 Fry

2008 Muskellunge 451 Fingerling 2010 Muskellunge 451 Fingerling 2012 Muskellunge 451 Fingerling 2013 Walleye 7,700 Large fingerling

29

Table 2. Kolmogorov-Smirnov test results for walleye length distribution comparisons from Middle Eau Claire Lake, Bayfield County, Wisconsin.

Table 3. Mean length (inches) for walleye from Middle Eau Claire Lake, Bayfield County, Wisconsin.

Table 4. Mean length (inches) for muskellunge from Middle Eau Claire Lake, Bayfield County, Wisconsin.

Table 5. Mean length (inches) for northern pike from Middle Eau Claire Lake, Bayfield County, Wisconsin.

Comparison D Statistic p Value1983 vs. 1993 0.48 < 0.00011993 vs. 1998 0.10 0.00081998 vs. 2004 0.39 < 0.00012004 vs. 2007 0.16 < 0.00012007 vs. 2010 0.20 < 0.00011983 vs. 2010 0.10 0.0124

Year Mean Length SD N1983 15.7 2.1 4461993 14.0 1.8 5761998 14.2 2.1 1,3642004 15.7 2.1 1,1772007 15.5 2.2 1,2162010 16.0 2.1 6212013 16.9 1.5 294

Year Mean Length SD N RSD - 34 RSD - 401993 33.7 4.9 7 67 171998 34.9 5.9 11 78 222004 32 5.8 18 50 202007 34.4 6.8 35 74 412010 36.5 4.6 20 79 262013 32.7 6.1 6 20 20

Year Mean Length SD N PSD RSD - 301993 16.0 5.1 45 15 01998 16.6 3.6 171 12 02004 19.9 6.3 48 50 52007 19.0 4.2 77 39 22010 17.6 5.0 79 38 22013 20.1 3.9 83 29 2

30

Table 6. Kolmogorov-Smirnov test results for bluegill length distribution comparisons from Middle Eau Claire Lake, Bayfield County, Wisconsin.

Table 7. Angler directed effort (%) for creel survey from Middle Eau Claire Lake, Bayfield County, Wisconsin.

Table 8. Length statistics for northern pike and bluegill measured during creel census on Middle Eau Claire Lake, Bayfield County, Wisconsin.

Comparison D Statistic p Value2004 vs. 2007 0.13 0.00032007 vs. 2010 0.48 < 0.00012010 vs. 2013 0.25 < 0.00012004 vs. 2013 0.19 < 0.0001

Species 1993 1998 2004 2007 2010 2013Walleye 37% 39% 37% 37% 32% 16%Muskellunge 10% 8% 11% 9% 14% 14%Northern Pike 15% 13% 8% 8% 11% 13%

Largemouth Bass 6% 6% 8% 7% 6% 10%Smallmouth Bass 2% 4% 8% 15% 11% 14%Bluegill 26% 19% 10% 11% 17% 24%Pumpkinseed 0% 0% 0% 0% 1% 1%Black Crappie 1% 4% 3% 2% 3% 6%Yellow Perch 2% 7% 14% 9% 4% 0%Rock Bass 1% 1% 0% 2% 1% 2%

Year

Year Mean Length SD N Mean Length SD N1993 19.7 2.7 112 6.9 0.7 6361998 20.2 3.5 65 7.3 0.8 3072004 23.5 2.9 16 7.6 0.8 98

2007 22.3 2.3 64 7.5 0.6 1792010 21.0 2.8 79 7.6 0.8 4022013 21.2 3.0 85 7.7 0.6 457

Northern Pike Bluegill

31

0.0

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1983198419851986198719881989199019911992199319941995199619971998199920002001200220032004200520062007200820092010201120122013

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ber/a

cre

Year Figure 1. Estimated density and 95% confidence intervals of adult walleye by year, Middle Eau Claire Lake, Bayfield County, Wisconsin, 1983 - 2013. Estimated density in 1983 was determined by mutiple census procedures and calculated using the Schumacher-Eschmeyer formula according to Krebs (1999). Estimated density after 1983 was calculated using the Chapman version of the Peterson formula (Ricker 1975), with GLIFWC surveys (open circles) utilizing electrofishing for both the marking and recpature samples and WDNR surveys (solid circles) utilizing fyke-netting and electrofishing for the marking and recapture samples, respectively. Horizontal line represents the mean density of all years comibined.

32

Figure 2. Percentage length frequency of fyke net catches for walleye by length interval in Middle Eau Claire Lake, Bayfield County, Wisconsin.

33

Figure 3. Proportional and relative (20) stock densities for walleye in Middle Eau Claire Lake, Bayfield County, Wisconsin.

0

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34

Figure 4. Percent distribution by age of walleye in Middle Eau Claire Lake, Bayfield County, Wisconsin.

0%

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3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

1993

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2013

35

Figure 5. Length at age of Middle Eau Claire walleye, Bayfield County, Wisconsin.

36

Figure 6. Relative abundance of age- 0 walleye determined by fall electrofishing, Middle Eau Claire Lake, Bayfield County, Wisconsin. Horizontal line represents the mean relative abundance of age-0 walleye for all years combined. No survey in 1989.

0

50

100

150

200

250

300

350

400

450

500

550

19851986198719881989199019911992199319941995199619971998199920002001200220032004200520062007200820092010201120122013

Num

ber o

f age

0 w

alle

ye/m

ile

Year

37

Figure 7. Relative abundance of bass (number/mile) collected during spring electroshocking surveys in Middle Eau Claire Lake, Bayfield County, Wisconsin.

0

2

4

6

8

10

12

19921993199419951996199719981999200020012002200320042005200620072008200920102011201220132014

Num

ber o

f fis

h/m

ile

Year

SMB

LMB

38

Figure 8. Percentage length frequencies for bluegill collected during panfish fyke net surveys in Middle Eau Claire Lake, Bayfield County, Wisconsin.

0%

5%

10%

15%

20%

25%

2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10

2004, N = 788

0%

5%

10%

15%

20%

25%

2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10

2007, N = 390

0%

5%

10%

15%

20%

25%

2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10

2010, N = 437

0%

5%

10%

15%

20%

25%

2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10Total length (inches)

2013, N = 1,231

39

Figure 9. Length at age of bluegill collected in Middle Eau Claire Lake, Bayfield County, Wisconsin.

0

2

4

6

8

10

12

2 3 4 5 6 7 8 9 10 11 12 13

Mea

n to

tal l

engt

h (in

)

Age (years)

2004

2010

2013

NAD Avg.

40

Figure 10. Angler catch and harvest of gamefish, Middle Eau Claire Lake, Bayfield County, Wisconsin.

0

1000

2000

3000

4000

1993 1998 2004 2007 2010 2013

Largemouth Bass

0

1000

2000

3000

4000

1993 1998 2004 2007 2010 2013

Smallmouth Bass

0

1000

2000

3000

4000

1993 1998 2004 2007 2010 2013

Walleye CatchHarvest

0

1000

2000

3000

4000

1993 1998 2004 2007 2010 2013Year

Northern Pike

Num

ber o

f fis

h

41

Figure 11. Angler catch and harvest of panfish, Middle Eau Claire Lake, Bayfield County, Wisconsin.

0

5000

10000

15000

20000

1993 1998 2004 2007 2010 2013

Bluegill

0

5000

10000

15000

20000

1993 1998 2004 2007 2010 2013Year

Yellow Perch

0

5000

10000

15000

20000

1993 1998 2004 2007 2010 2013

Num

ber o

f fis

h

Black Crappie

CatchHarvest

42

Appendix Table 1. Proportional and relative stock density values. Species Stock Size (in) Quality Size (in) Preferred Size (in) Bluegill 3 6 8 Largemouth Bass 8 12 15 Muskellunge 20 30 38 Northern Pike 14 21 28 Smallmouth Bass 7 11 14 Walleye 10 15 20

Appendix Figure 1. Lake map, Middle Eau Claire Lake, Bayfield County, Wisconsin.