lake owen walleye and bass update bayfield county, wi...lake owen is a low productivity lake that...

Lake Owen Walleye and Bass Update

Bayfield County, WI

WIBIC: 2900200

Author with Lake Owen walleye, 2014. Photo by Scott Toshner

Kirk Olson

Fisheries Technician – LTE

Brule Fisheries Management Team

Wisconsin Department of Natural Resources

April, 2015

Executive Summary

Lake Owen is a low productivity lake that supports a popular smallmouth bass, largemouth bass and

walleye fishery. Since 1988, walleye abundance has declined while largemouth bass abundance has

increased in Lake Owen. This shift may be the result of overexploitation of walleye, negative interactions

between walleye and largemouth bass, or changes in habitat conditions (e.g. temperature, productivity).

Since the last fisheries report (Toshner, 2008), several fisheries surveys have been completed including a

mark-recapture walleye population estimate (2013), annual fall juvenile walleye recruitment surveys and

late spring stocking success and bass relative abundance surveys.

Concerns over Lake Owen’s shifting gamefish community have resulted in several changes to

fisheries management in Lake Owen. Between 2009 and 2011, regulations intended to reduce harvest of

walleye were implemented, minimum length limits for smallmouth and largemouth bass were removed

and stocking density of large fingerling walleye was increased. In addition, the model used to assign

walleye harvest quotas was changed to more accurately reflect the recruitment status of Lake Owen’s

walleye population. This resulted in reduced harvest quotas in years when the model was used to calculate

safe harvest levels.

Since these changes have been implemented, modest changes to the gamefish community have

occurred. In 2013 and 2014, largemouth bass abundance declined and recruitment of age-1 walleye

increased. However, overall walleye density did not increase from 2007.

Our results indicate that increased stocking of large fingerling walleye had limited impact on

walleye abundance. In 2013, only 8% of the adult population could be attributed to stocking efforts.

Additionally, we did not detect a significant increase in juvenile recruitment in years when stocking

occurred. Lake Owen’s oligotrophic nature and abundance of predators may be limiting the success of

stocking.

Although changes in harvest quotas and angling regulations potentially influenced exploitation of

walleye, smallmouth bass and largemouth bass, we were unable to assess the impact of these changes

because the most recent creel occurred in 2007. Similarly, we could not attribute recent changes in the

gamefish community to regulation changes without estimates of exploitation or incorporation of a

reference lake in our analysis to account for environmental variability. Data are currently being collected

that will provide reference lakes to compare to Lake Owen, results of these will be available in 2019.

Our management recommendations are: 1) Increase walleye abundance to the ceded territory

large stocked lake average of 2.3 adults/acre from 1.2 adults/acre found in the 2007 Lake Owen survey by

2019 through maintaining conservative regulations established in 2011 and by stocking of large walleye

fingerling, 2) cease stocking activities after the next walleye population assessment in 2019 if stocked fish

do not contribute at least 20%, on average, to each stocked cohort between age 4 and 10 or if the mean

cost per stocked age 4 and 5 recruit is greater than $250, 3) manage largemouth bass and smallmouth bass

separately and decrease largemouth bass abundance from 17.5 fish/mile to 1.2 fish/mile by 2019 , 4)

carry out a creel survey in tandem with the 2019 walleye population assessment to determine exploitation

of walleye, smallmouth bass and largemouth bass.

Introduction

Lake Owen is a deep, oligotrophic drainage lake located at the headwaters of Long lake Branch in

southern Bayfield County, WI. It has a surface area of 1,323 acres, mean depth of 27 feet and maximum

depth of 95 feet. Lake Owen supports a diverse fish community and a popular walleye (Sander vitreus),

smallmouth bass (Micropterus dolomieui) and largemouth bass (Micropterus salmonides) fishery (Scholl

1996, Toshner 2009).

A 2007 assessment of the lakes fishery revealed that abundance of walleye had declined while

largemouth bass densities increased (Toshner 2009). This caused concern that a combination of

exploitation, changing habitat and negative interactions between walleye and largemouth bass were

resulting in a shift toward a gamefish community dominated by Centrarchids (Toshner 2009). To improve

Lake Owen’s walleye fishery, several changes in fisheries management have occurred since the last

fisheries assessment.

Between 2009 and 2013, large fingerling walleye (4.6 -7.0 in) were stocked at an average rate of

8.4 fish/acre, a significant increase in stocking density from previous years. Earlier stocking of walleye

fry, fingerling (1.5 - 4.0 in) and large fingerling at low rates were largely unsuccessful in Lake Owen

(Scholl 1996, Toshner 2009). It was expected that increased survival experienced by large fingerling

walleye stocking (e.g. Kampa and Hatzenbeler 2009) would result in increased walleye recruitment.

Along with stocking efforts, walleye minimum length limits were increased from 15 in to 18 in

and bag limits were decreased from 5 to 3 in 2011, though bag limits after adjustment for tribal harvest

remained at 2. Walleye exploitation in 2007-2008 was 45%, exceeding the maximum harvest for lakes in

the ceded territory of 35%, recommended by Staggs et al. (1990). Increased minimum length limits were

intended to reduce overall harvest and protect spawning female walleye, improving natural recruitment

(Toshner 2009). Concurrent with walleye regulation changes, minimum length limits were removed for

smallmouth and largemouth bass and anglers were encouraged to harvest largemouth bass. The intention

of this change was to reduce largemouth bass abundance and possible negative interactions with walleye

(Toshner 2009).

The purpose of this report is to summarize trends in abundance and population structure of

walleye and bass (smallmouth and largemouth) over the past 25 years and to evaluate the effectiveness of

management activities since 2009.

Methods

Adult walleye abundance was estimated in 1988, 1994, 1999, 2001, 2003, 2007 and 2013 using

standardized mark-recapture techniques described by Cichosz (2014). Spawning walleye were captured

shortly after spring ice-out using fyke nets in 1988, 1994, 2007 and 2013 and by AC electrofishers in

1999, 2001 and 2003. All walleye captured were measured to the nearest 0.1in and sex was determined

for mature fish. Adult walleye (sexually mature or of unknown sex and ≥ 15”) were marked with a fin

clip. One to two days after marking, the entire shoreline was electrofished in one night and captured

walleye were measured and checked for marks. Adult walleye abundance was estimated using the

Chapman modification of the Peterson Estimator:

𝑁𝑁 =(𝑀𝑀 + 1)(𝐶𝐶 + 1)

(𝑅𝑅 + 1)− 1

with variance estimated by the equation:

𝑉𝑉(𝑁𝑁) =(𝑀𝑀 + 1)(𝐶𝐶 + 1)(𝑀𝑀 − 𝑅𝑅)(𝐶𝐶 − 𝑅𝑅)

(𝑅𝑅 + 1)2(𝑅𝑅 + 2)− 1

where N is the estimated abundance, M is the total number of marked fish, C is the total number of fish

captured during the recapture period, R is the number of marked fish captured during the recapture period

and 𝑉𝑉(𝑁𝑁) is the variance. Walleye densities were compared to the mean density for lakes in northwestern

Wisconsin (Bayfield, Douglas, Washburn, Burnett, and Sawyer Counties) sustained by natural

reproduction or stocking. Simple linear regression was used to test for trends in abundance (logx

transformed) over time.

Walleye spines were subsampled from each 0.5-in length group during spring netting or

electrofishing in 1988, 1994, 2007 and 2013. Spines were cross sectioned and viewed at 100X

magnification to determine age (Margenau 1982). A length-age key was developed following the methods

outlined by Isely and Grabowski (2007) allowing an estimate of the age distribution for the entire sample.

Growth of male and female walleye was modeled separately using the von Bertlanffy growth equation:

𝑙𝑙𝑡𝑡 = 𝐿𝐿∞(1− 𝑒𝑒−𝐾𝐾(𝑡𝑡−𝑡𝑡0))

where 𝑙𝑙𝑡𝑡 is length at time 𝑡𝑡, 𝐿𝐿∞ is asymptotic length, 𝐾𝐾 is a growth parameter and 𝑡𝑡0 is time at length 0.

Parameters of the von Bertalanffy model were estimated in the non-linear platform of SAS-JMP using the

Gauss-Newton method. Mean length at age and parameters of the von Bertlanffy Growth model were

compared to the Northwestern Wisconsin mean for each sex.

Young of the year (YOY) walleye were sampled in the early fall once water temperatures

dropped below 70°F. The entire shoreline of Lake Owen was sampled using AC electrofishing annually

between 1985 and 2014, except in 1987, 1989 and 1998. Catch per mile of shoreline sampled of YOY

walleye were compared to the mean for lakes sampled between 1990 and 2013 in Northwestern

Wisconsin (Bayfield, Douglas, Washburn, Burnett, and Sawyer Counties) sustained by natural

reproduction or stocking. A non-parametric Mann-Whitney test was performed to compare relative

abundance of YOY walleye between years where stocking occurred and when it did not or occurred after

sampling. Linear regression was used to examine the trend in relative abundance of YOY walleye. Catch

per unit effort (CPUE) of YOY walleye was log (x+1) transformed to meet assumptions of linear

regression.

In order to evaluate effectiveness of large fingerling walleye stocking, an effort was made to mark

stocked fish with fin clips beginning in 1995. However, in 2006, 2008, 2009 and 2011 a portion of

stocked walleye were not fin clipped prior to stocking. In all, 72% of all large fingerling walleye stocked

between 1995 and 2013 received fin clips prior to stocking. Following stocking, late spring electrofishing

samples were carried out in 2002, 2008, 2010, 2011, 2012, 2013 and 2014 to assess the survival and

contribution of stocked walleye to the age 1 cohort. Contribution of marked stocked fish to each age

cohort was estimated for the 2013 spring fyke netting sample by assigning ages to marked fish using an

age length key for age 3 (2010 cohort) and age 4 (2009 cohort). The abundance of age 3 and age 4

hatchery fish were estimated by multiplying the population estimate by the proportion of hatchery fish

composing each age class. Cost of each stocking event was estimated using mean cost per stocked large

fingerling and Mississippi strain walleye multiplied by the number of fish stocked (e.g. Sand 2012). Cost

per recruit was then estimated by dividing the total cost by the number of fish recruited to age 3 and age 4

cohorts.

Largemouth and smallmouth bass were sampled between May 12th and June 20th by

electrofishing in 1975, 1988, 1994, 2002, 2007, 2013 and 2014. In 1988, 1994, 2002 and 2007 the entire

shoreline was sampled. In 1975, 15.2 miles of shoreline were sampled and in 2014, 10.0 miles were

sampled. Catch per mile of large and smallmouth bass were compared to the mean for lakes sampled

between 1990 and 2013 in Douglas and Bayfield Counties.

Size structure of each species was assessed using proportion stock density (PSD) or proportion

stock density- preferred (PSDP) following the equation:

𝑃𝑃𝑃𝑃𝑃𝑃 𝑜𝑜𝑜𝑜 𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃(%) =𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑒𝑒𝑜𝑜 ≥ 𝑠𝑠𝑠𝑠𝑒𝑒𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑒𝑒𝑠𝑠𝑙𝑙𝑒𝑒𝑛𝑛𝑠𝑠𝑡𝑡ℎ

𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑒𝑒𝑜𝑜 ≥ 𝑠𝑠𝑡𝑡𝑜𝑜𝑠𝑠𝑠𝑠 𝑠𝑠𝑠𝑠𝑠𝑠𝑒𝑒× 100

where 𝑠𝑠𝑡𝑡𝑜𝑜𝑠𝑠𝑠𝑠 𝑠𝑠𝑠𝑠𝑠𝑠𝑒𝑒and 𝑠𝑠𝑠𝑠𝑒𝑒𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑒𝑒𝑠𝑠 𝑙𝑙𝑒𝑒𝑛𝑛𝑠𝑠𝑡𝑡ℎ are specific to each species (Neumann et al. 2012, Appendix

Table 1). PSD and PSDP values were compared to similar lakes across the state using the WDNR

Fisheries Assessment Classification Tool (FACT). Shifts in PSD or PSDP with time were assessed using

linear regression. PSD and PSDP were log(x) transformed prior to statistical analysis, if necessary, to

improve normality. Length distributions were compared among years using a non-parametric Kruskal-

Wallis and post hoc Steel-Dwass multiple comparison tests (to control for familywise error rate).

All statistical tests were performed in SAS-JMP using a significance level of 0.05.

Results

Walleye

Adult walleye densities have been low since 1988 (mean = 1.6 fish/acre, range = 0.8 – 3.0

fish/acre) relative to the mean for lakes sustained by stocking or natural reproduction in northwestern

Wisconsin (mean ±1S.D. = 3.6 ± 4.4 fish/acre). Between 1988 and 2013 abundance declined from a high

of 3 fish/acre in 1988 to less than 1 fish/acre in 2013 (r2=0.77, p = 0.01). Between 1988 and 2003

densities declined precipitously but have since stabilized (Figure 1). In 2013, adult walleye density was

0.87 ± 0.38 fish/acre (mean ± 95% C.I.).

There were shifts in the length frequency distribution of walleye between 1988 and 2013 (Figure

2). Length frequency distributions of walleye sampled in 1999 and 2003 were skewed towards smaller

fish than all other years and the length frequency distribution of walleye in 2007 was skewed to larger fish

than all other years (Table 1). Walleye PSD was high throughout the study period (mean ± 1S.D. = 81 ±

10) and in the 81st percentile for lakes with similar abiotic characteristics (FACT). PSD-P ranked lower

than PSD (46th percentile) and was more variable among years (25 ± 19, mean ± 1S.D).

Walleye age structure was variable among the four years sampled. In the two earliest surveys,

1988 and 1994, more than half of all walleye sampled were between ages 4-6. In 2007 and 2013 the age

distribution was more evenly spread across ages 2-12 (Figure 3). The Steel-Dwass non-parametric

multiple comparison test revealed that 2007 had a significantly older age distribution (all comparisons,

p<0.001) than all other years and 2013 had an older age distribution than 1988 (p = 0.049) but not

significantly different from 1994 (p = 0.11, Table 2).

Mean length at age was dimorphic for male and female walleye (Figure 4). Separated by sex, the

Von-Bertalanffy growth model fit mean length at age data well (r2 = 0.90- 0.99). Estimated growth

parameters (k) for female and male walleye were higher than the mean for Northwestern Wisconsin

(Table 3). Mean maximum length (L∞) for male and female walleye was 23 and 27, respectively, and

similar to the northwestern Wisconsin average for males and lower for females (Table 3).

The mean catch per mile of YOY walleye in fall electrofishing surveys was lower than the mean

for stocked and non-stocked lakes in Northwestern Wisconsin (Lake Owen = 7.5 ±12.0, Northwestern

Wisconsin = 13.0 ± 31.7, mean ± 1 S.D.). Between 1985 and 2012, YOY catch rates have declined

(r2=0.69, p<0.001). Since 1997 YOY catch rates have not surpassed five fish per mile and YOY walleye

were absent in 2004, 2005 and 2010 samples (Figure 5). In 2014, YOY catches were 0.47 fish/mile.

YOY catch rates were similar in years when large fingerling walleye were stocked prior to fall

sampling (Mann-Whitney, p = 0.85) and the catch rate was not correlated to number of large fingerling

walleye stocked the previous fall (r2=0.20, p = 0.26). Late spring stocking evaluations revealed that the

contribution of hatchery fish to the age-1 walleye population was highly variable (9.8 - 100%) and higher

in years when overall catch rates were low (Figure 6). Adult walleye with hatchery marks (8 fish total)

composed 6% of all adult walleye sampled during fyke netting in the spring of 2013. Assuming unmarked

fish stocked in 2006, 2008 and 2009 contributed to the population in the same proportion as marked fish,

roughly 8% of the 2013 adult walleye population were of hatchery origin. Walleye stocked in 2011

composed 8% of the age 3 cohort and, assuming marked and unmarked walleye experienced the same

mortality rate, walleye stocked in 2009 composed 10% of the age 4 cohort. Estimated cost of age 3 and 4

stocked recruits were $1610.07/recruit and $692.87/recruit (2012 US dollars), respectively.

Largemouth and Smallmouth Bass

Largemouth bass were absent from late spring electrofishing runs in 1975 and 1988, though other

surveys indicated their presence in the lake. Largemouth bass first appeared in late spring electrofishing

surveys in 1992, increased in abundance to a high of 19.4 fish/mile in 2007 and declined to 8.3 fish/mile

in 2014 (Figure 7). Between 1994 and 2014, size structure of largemouth bass was largest in 2013 and

2014 and smallest in 2002 (Figure 9, Table 5). Catch rates of largemouth bass greater than 14 in increased

sharply from 0.9 fish/mile in 1994 to 5.2 fish/mile in 2007 and have since stabilized between 5 and 7

fish/mile in 2013 and 2014. Largemouth bass PSD and PSDP did not exhibit significant trends between

1994 and 2014 (r = 0.47 - 0.48, p > 0.10). In 2014, PSD was 83, in the 85th percentile for largemouth bass

populations statewide (FACT).

Smallmouth bass relative abundance has been slightly higher than the average for Douglas and

Bayfield County lakes (Lake Owen = 12.5 ± 5.4, Douglas and Bayfield County = 6.8 ± 7.0 fish/ mile

mean ± 1S.D.) and did not exhibit a significant trend over the study period (linear regression, r2 = 0.49, p

= 0.19; Figure 7). Size structure of smallmouth bass was largest in 2013, smallest in 1975 and similar

among all other years (Table 4). Similarly, PSDP exhibited a positive linear trend between 1975 and 2014

(r2 = 0.98, p <0.001). In 2014, the PSD for smallmouth bass was 52, in the 33rd percentile for smallmouth

bass populations statewide (FACT

Discussion

Walleye

Adult walleye densities in Lake Owen have declined from 1988 to 2013 and the adult population

structure has shifted to larger and older fish. Concurrently, walleye recruitment has declined from 1985 to

2014. Several factors may be attributed to the decline of walleye in Lake Owen, including: negative

interactions with largemouth bass, habitat change and overexploitation.

Largemouth bass may negatively influence walleye abundances through predation on juveniles

(Santucci and Wahl 1993, Fayram et al. 2005, Repp 2012). Nate et al. (2003) identified that lakes in

northern Wisconsin with largemouth bass tend to have walleye populations that are sustained through

stocking, suggesting a negative interaction between largemouth bass and walleye recruitment. Our results

were consistent with these findings, juvenile walleye recruitment declined concurrent with increased

largemouth bass abundance, suggesting that largemouth bass may be reducing walleye recruitment in

Lake Owen.

Although we did not measure habitat variables, changes in temperature and productivity due to

climate change and development, respectively, may have influenced walleye abundance in Lake Owen.

Garrison (2005) identified that productivity in Lake Owen has increased over the past 100 years based on

fossil diatoms. During this same time period, Wisconsin’s mean annual temperature has also increased,

likely resulting in warmer lake temperatures and shorter periods of ice cover, similar to changes that have

been observed in other high latitude lakes (Magnuson et al. 2000, Austin and Colman 2007, Coulson et al.

2011). Increased temperatures and productivity have the potential to limit walleye habitat availability

during summer by reducing availability of oxygenated waters within their optimal temperature range (20-

28°C, Hokanson 1977).

High exploitation may have also reduced walleye abundances in Lake Owen since 1988. Safe

harvest levels for walleye in Lake Owen are based on mark-recapture population estimates, in the two

years after a survey, or by lake area regression models developed for lakes sustained by natural

recruitment, stocking, or intermittent natural recruitment (Hansen 1991, Beard et al. 2003). Harvest

quotas based on the natural recruitment model are generally greater than stocked and intermittent

recruitment models (e.g. Cichosz 2011). In 2009, the regression model used to estimate harvest quotas in

Lake Owen was changed from natural to stocked as a result of limited natural recruitment, following the

recruitment code classification system developed by the Wisconsin Fisheries Technical Working Group.

Because natural recruitment was low for several years prior to 2007 (Figure 5), exploitation may have

been high prior to 2007, when the natural recruitment regression model was used to determine harvest

quotas.

Along with changes to the walleye harvest quota calculations, minimum length limits were

increased from 15 in to 18 in in 2011. The objectives of this change were to reduce exploitation and

allow females at least one opportunity to spawn before being vulnerable to angler exploitation, potentially

increasing natural recruitment. The effectiveness of daily bag and minimum length limits in reducing

harvest and increasing abundances has been mixed (Fayram et al. 2001, Stone and Lott 2002, Isermann

2007). A 15 in minimum length limit for walleye in Wisconsin reduced walleye exploitation but did not

have an impact on population structure (Fayram et al. 2001). In a South Dakota impoundment, a

combination of increased minimum length limit and reduced bag limit resulted in lower overall harvest,

but after three years harvest returned to pre-regulation levels (Stone and Lott 2002). Because a creel

survey has not been carried out since 2007, we could not determine whether increased minimum length

limits changed angler exploitation. Although slight increases in recruitment have occurred since 2011,

these changes could be attributed to several other changes (e.g. weather conditions, decline in largemouth

bass abundance). To account for these variables, future assessments should include a control or reference

lake.

Similar to the findings of other fisheries managers, stocking was largely unsuccessful in Lake

Owen (Scholl 1996, Toshner 2009). YOY walleye abundance was not greater in stocked years and

stocked fish generally made a small contribution to age-1 recruitment, with stronger year classes

originating from natural reproduction. Additionally, the cost of adult recruits was high. These results are

consistent with several other studies, which found low success rates for supplemental walleye stocking

(Li et al. 1996, Parsons and Pereira 2001, Jennings et al. 2005). Both abiotic (e.g. temperature) and biotic

(e.g. prey availability, predation) factors may influence survival of stocked fish (Donovan et al. 1997,

Hoxmeier et al 2006). Low productivity and the presence of largemouth bass, a potential predator of

stocked walleye (Santucci and Wahl, 1993), could be responsible for limited survival of stocked fish in

Lake Owen.

Largemouth and Smallmouth bass

Largemouth bass abundance and size structure have increased since 1994, when they first

appeared in a late spring electrofishing survey. Scholl (1996) attributed the apparent increase in

abundance to unusually warm and dry conditions, which he believed favored largemouth bass

recruitment. In 2013 and 2014, largemouth bass abundance declined while size structure shifted toward

larger fish, indicating reduced recruitment. This decline in largemouth bass is likely not the result of

increased harvest as we would expect declines in size classes targeted by anglers (fish>13 in) prior to

declines in recruitment. The decline in recruitment also does not appear to be associated with density

dependent processes (e.g. cannibalism) as catches of largemouth greater than 14 in remained relatively

unchanged from 2007. Largemouth bass recruitment to age 1 is often influenced by overwinter survival,

especially at higher latitudes (Fullerton et al. 2000). Between 1990 and 2012 northwestern Wisconsin

experienced a period of warmer than average winters, with 17 of the past 22 years having higher than

average winter mean temperatures (Wisconsin State Climatology Office). In the past two years mean

winter temperatures have dropped to more than three degrees below average, possibly reducing survival

and subsequent recruitment of largemouth bass in the winters of 2012-2013 and 2013-2014.

Lake Owen supports a very popular, primarily catch and release, smallmouth bass fishery

(Toshner 2009). Although variable, relative abundance of smallmouth bass has not exhibited any overall

trends between 1988 and 2014. Since 1988, size structure has improved, with a larger proportion of fish

now greater than 14 in. In 2011, minimum length limits for both smallmouth and largemouth bass were

removed in hopes of greater angler harvest of largemouth bass. In order to maintain the quality of the

popular smallmouth bass fishery, efforts should be made to regulate angler harvest separately from

largemouth bass.

Evaluation of 2009 Management Objectives and Future Recommendations

1. Decrease largemouth bass abundances to 1.2 fish/mile by 2020 by reducing regulations on angler

harvest (Toshner 2009).

Largemouth bass relative abundance has declined to 8.3 fish/mile in 2014. Declines in recruitment

and little change in relative abundance of fish >13”, indicate that the decline is not the result of angler

exploitation. In light of recent declines, a reduction to 1.2 fish/mile by 2020 appears to be an

attainable objective. We recommend that largemouth bass and smallmouth bass be regulated

separately, in order to protect the popular smallmouth bass fishery. Future work should incorporate

creel surveys to allow an assessment of the effectiveness of this regulation change and possible

impacts on the smallmouth bass fishery, if smallmouth bass continue to be managed with largemouth

bass.

2. Increase walleye abundance to the ceded territory large stocked lake average of 2.3 adults/acre

from1.2 adults/acre in 2007 by 2020 by increasing large fingerling stocking to 10 fish/acre, reducing

maximum angler bag limits from 5 to 3 fish and increasing minimum length limits to 18 in (Toshner

2009).

Walleye abundances have not changed significantly since 2007. Increased stocking intensity of large

fingerling has not resulted in increased juvenile recruitment or adult abundances. Stocked fish made

up a small portion of the adult population sampled in 2013. We recommend that stocking be ceased if,

in 2019, mean contribution to stocked year classes, between ages 4 and 10, is not at least 20%, on

average, and if mean cost per age 4 and 5 recruit is more than $250 (2012 US Dollars).

3. Monitor effects of proposed changes by estimating walleye and bass abundances every 6 years,

marking stocked walleye, conducting spring stocking assessments and conducting at least one creel

survey prior to 2020 (Toshner 2009).

Fisheries assessment surveys, including a walleye population estimate in 2013, have been carried out

as planned. Given the previous management objective, assessment activities aimed at determining the

effectiveness of stocking in Lake Owen (i.e. marking hatchery fish, spring electrofishing) should be

continued. Ageing structures should be collected from all hatchery-origin adult walleye captured

during future surveys to allow a more accurate assignment of ages to stocked fish. A creel survey

should be carried out in conjunction with the 2019 walleye population survey to allow for an

evaluation of the 2011 angling regulation changes in reducing angler harvest.

References

Austin, J. A., S. M. Colman. 2007. Lake Superior water temperatures are increasing more rapidly than regional air temperatures: A positive ice-albedo feedback. Geophysical Research Letters 34:1-5.

Beard, T. D., P. W. Rasmussen, S. Cox, and S. R.Carpenter. 2003. Evaluation of a management system

for a mixed walleye spearing and angling fishery in Northern Wisconsin. North American Jouranl of Fisheries Management 23:481-491.

Cichosz, T.A. 2011. 2008-2009 Ceded territory fishery assessment report. Wisconsin Department of

Natural Resources. Administrative Report 68, Madison.

Cichosz, T.A. 2014. 2012-2013 Ceded territorty fishery assessment report. Wisconsin Department of Natural Resources. Administrative Report 75, Madison.

Coulson, A., S. Dunwoody, R. C. Lathrop, D. S. Liebl, J. J. Magnuson, S. Poplun, T. Sinclair, J. R. Sullivan, D. J. Watermolen, D. Webb, editors. 2011. Wisconsin’s changing climate: impacts and adaptation. 2011. Wisconsin Initiative on Climate Change Impacts. Nelson Institute for Environmental Studies, University of Wisconsin- Madison and the Wisconsin Department of Natural Resources, Madison, Wisconsin.

Donovan, N., R. A. Stein, and M. M. White. 1997. Enhancing Percid stocking success by understanding

age-0 piscivore-prey interactions in reservoirs. Ecological Applications 7(4):1311-1329. Fayram, A. H., S. W. Hewett, S. J. Gilbert, S. D. Plaster, and T. D. Beard, Jr. 2001. Evaluation of a 15-

inch minimum length limit for walleye angling in Northern Wisconsin. North American Jouranl of Fisheries Management 21:816-824.

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.

Fullerton, A. H., J. E. Garvey, R. A. Wright, and R. A. Stein. 2001. Overwinter growth and survival of

largemouth bass: interaction among size, food, origin and winter severity.

Garrison, P. J. 2005. Assessment of the water quality in Lake Owen, Bayfield County Wisconsin by the use of fossil diatoms. Wisconsin Department of Natural Resources, Bureau of Integrated Science Services. PB-SS-1014.

Hansen, M. J., T. D. Beard, Jr., and S. W. Hewett. 2000. Catch rates and catchability of walleye in

angling and spearing fisheries in Northern Wisconsin Lakes. North American Journal of Fisheries Management 20:109-118.

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 120: 620-628.

Hokanson, K. E. F. 1977. Temperature requirements of some percids and adaptations to the seasonal

temperature cycle. Journal of Fisheries Research Board of Canada 34: 1524-1500. Hoxmeier, R. J., D. H. Wahl, R. C. Brooks, R. C. Heidinger. 2006. Growth and survival of age-0 walleye

(Sander vitreus): interactions among walleye size, prey availability, predation and abiotic factors. Canadian Journal of Fisheries and Aquatic Sciences 63(10):2173-2182.

Isermann, D. A. 2007. Evaluating walleye length limits in the face of population variability: case histories

from Western Minnesota. North American Journal of Fisheries Management 27:551-568. Isely, J. J., and T. B. Grabowski. 2007. Age and Growth. Pages 187-228 in C. S. Guy and M. L. Brown,

editors. Analysis and interpretation of freshwater fisheries data. American Fisheries Society, Bethesda, Maryland.

Jennings, M. J., J. M. Kampa, and G. R. Hatzenbeler. 2005. Evaluation of supplemental walleye stocking

in Northern Wisconsin lakes. North American Journal of Fisheries Management 25:1171-1178.

Kampa, J. M. and G. R. Hatzenbeler. 2009. Survival and growth of walleye fingerlings stocked at two sizes in 24 Wisconsin Lakes. North American Journal of Fisheries Management 29: 996-1000.

Li, J., Y. Cohen, D. H. Schupp, and I. R. Adelman. 1996. Effects of walleye stocking on year-class

strength. North American Journal of Fisheries Mangement 16:840-850.

Magnuson, J. J., D. M. Robertson, B. J. Benson, R. H. Wynne, D. M. Livingstone, T. Arai, R. A. Assel, R. G. Barry, V. Card, E. Kuusisto, N. G. Granin, T. D. Prowse, K. M. Stewart, and V. S. Vuglinski. 2000. Historical trends in lake and river ice cover in the northern hemisphere. Science 1743-1746.

Margenau, T. L., 1982. Modified procedure for aging walleye by dorsal spine sections. Progressive Fish- Culturist 44:204.

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.

Neumann, R. M. and M. S. Allen. 2007. Size structure. Pages 375-421 in C.S. Guy and M. L. Brown,

editors. Analysis and interpretation of freshwater fisheries data. American Fisheries Society, Bethesda, Maryland.

Neumann, R.M., C. S. Guy and D. W. Willis. 2012. Length, weight and associated indices. Pages 637- 676 in A. V. Zale, D. L. Parrish, and T. M. Sutton, editors. Fisheries techniques, 3rd edition. American Fisheries Society, Bethesda, Maryland.

Parsons, B. G., D. L. Pereira. 2001. Relationship between walleye stocking and strength in three

Minnesota lakes. North American Journal of Fisheries Management 21:801-808. Repp, A. J. 2012. Investigating interactions between walleye and black bass in Northern Wisconsin lakes.

M.Sc. Thesis. University of Wisconsin Stevens Point.

Santucci, V.J., and D. H. Wahl. 1993. Facros influencing survival and growth of stocked walleye (Stizostedion vitreum) in a centrarchid-dominated impoundment. Canadian Journal of Fisheries and Aquatic Science. 50:1548-1558.

Sand, C. 2012. Diamond lake stocking evaluation. Wisconsin Department of Natural Resources , Fisheries Management Report, Brule Field Office

Scholl, D.K. 1996. WDNR memorandum- 1994 fishery survey summary – Lake Owen, Bayfield County.

Brule – Office File.

Stone, C., and J. Lott. 2002. Use of a minimum length limit to manage walleyes in Lake Francis Case, South Dakota. North American Journal of Fisheries Management 22:975-984.

Staggs, M.D., 1989. Walleye angling in the ceded territorty, Wisconsin, 1980-1987. Wisconsin

Department of Natural Resources, Fisheries Management Report 144, Madison. Toshner, S. 2009. Fisheries Survey – Lake Owen, Bayfield County 2007-2008. Wisconsin Department of

Natural Resources, Fisheries Management Report, Brule Field Office.

Table 1. Mean length (in.), standard deviation and results from non-parametric multiple comparison test (Steel-Dwass Method) for adult walleye length distributions from Lake Owen, Bayfield County, Wisconsin. Years connected with the same letter do not have significantly different distributions.

Year Mean (±1 S.D.) Connecting Letters 1999 16.4 (2.2) A

2001 16.5 (2.4) A 1988 17.5 (3.6)

B

2003 17.9 (2.4)

B 1994 18.4 (3.8)

B

2013 18.5 (2.9)

B 2007 20.8 (3.6) C

Table 2. Mean age (years), standard devation and results of Non-parametric multiple comparison test (Steel-Dwass Method) for adult walleye in Lake Owen, Bayfield County, Wisconsin. Years connected with the same letter do not have significantly different distributions.


1994 5.9 (2.7) A B 2013 6.8 (3.2)

B

2007 8.1 (3.1) C

Table 3. Parameters of Von-Bertalanffy estimated for adult walleye captured in 1994, 2007, 2013 in Lake Owen, Bayfield County, Wisconsin and the Northwest Wisconsin regional average separated by gender.

Year Sex k L∞ r2 1994 F 0.20 27.7 0.90 2007 F 0.18 27.9 0.97 2013 F 0.21 25.6 0.96 Owen Mean F 0.20 27.0 0.94 NW WI Mean F 0.12 30.2 0.99 1994 M 0.30 20.8 0.90 2007 M 0.21 25.6 0.93 2013 M 0.15 22.5 0.93 Owen Mean M 0.22 22.9 0.92 NW WI Mean M 0.15 22.7 0.98

Table 4. Mean length (in.), standard deviation and results from non-parametric multiple comparison test (Steel-Dwass Method) for smallmouth bass length distributions from Lake Owen, Bayfield County, Wisconsin. Years connected with the same letter do not have significantly different distributions.

Year Mean (±1 S.D.) Connecting Letters 1975 8.9 (2.7) A 1994 10.7 (2.9)

B

1988 10.8 (2.7)

B 2002 11.0 (3)

B

2014 11.2 (3.5)

B C 2007 11.4 (2.9)

B

2013 12.4 (3.1) C

Table 5. Mean length (in.), standard deviation and results from non-parametric multiple comparison test (Steel-Dwass Method) for largemouth bass length distributions from Lake Owen, Bayfield County, Wisconsin. Years connected with the same letter do not have significantly different distributions.


2007 12.1 (2.6)

B 1994 12.5 (2.1)

B

2014 13.6 (2.7)

C 2013 14 (2.1) C

Figure 1. Density of adult walleye (± 95% C.I.) estimated from mark-recapture surveys in Lake Owen, Bayfield County, Wisconsin. Gray circles represent years where mark-recapture survey were carried out by GLIFWC, black circles represent years where the WDNR was responsible for the surveys.

Figure 2. Length frequency of walleye captured by electrofishing (1999,2001 and 2003) and fyke nets (1988,1994,2007 and 2014) in Lake Owen, Bayfield County, Wisconsin.

Length (In)

Prop

ortio

n n = 393 n = 292

n = 1148 n = 984

n = 604 n = 353

n = 138

Figure 3. Proportion of adult walleye in each age class from Lake Owen, Bayfield County, Wisconsin.

Age (Years)

Prop

ortio

n

n = 393 n = 296

n = 353 n = 138

Figure 4. Mean length at age for male(bottom) and female(top) walleye from Lake Owen, Bayfield County, Wisconsin (circles) and the average for male walleye in northwestern Wisconsin (solid line).

Figure 5. Catch per mile of YOY walleye sampled in the fall of the year between 1985 and 2012. Gray bars represent years when small or larger fingerling walleye were stocked prior to sampling. White bars represent years when walleye were not stocked or not stocked prior to sampling. Black bar represents years when timing of sample in relation to stocking was unknown. Asterisks indicate years that were not sampled.

Figure 6. Catch per mile of age 1 walleye in late spring electrofishing samples and contribution of catch from natural and artificial recruitment in Lake Owen, Bayfield County, Wisconsin.

Figure 7. Catch per mile of smallmouth (SMB) and largemouth bass (LMB) during late spring electrofishing in Lake Owen, Bayfield County, Wisconsin.

Figure 8. Proportion of smallmouth bass in each inch class from Lake Owen, Bayfield County, Wisconsin.

Length (In)

0.000.050.100.150.20

3132014

Prop

ortio

n

n = 299 n = 321

n = 564 n = 264

n = 218 n = 378

n = 54

Figure 9. Proportion of largemouth bass in each inch class from Lake Owen, Bayfield County, Wisconsin.

Length (In)

0.000.050.100.150.20

3132014

Prop

ortio

n

n = 92 n = 392

n = 484 n = 266

n = 84

Appendix Table 1. Proportional stock density values.

Species Stock Size (in) Quality Size (in) Preferred Size (in) Largemouth Bass 8 12 15 Walleye 10 15 20 Smallmouth Bass 7 11 14

Appendix Table 2. Fish stocking history of Lake Owen, Bayfield County, Wisconsin.

Year Species Number Stocked Age/Size 1933 Walleye 703,700 Fry

Black Bass 1,362 Unkown

1935 Walleye 825,900 Fry

Black Crappie, Bluegill 900 Unkown

1936 Walleye 1,587,600 F

Sunfish 560 Unkown

Bluegill 560 Unkown

1938 Walleye 1,559,640 Fry

Largemouth Bass 2,000 Fry

1939 Walleye 1,000,000 Fry


1940 Walleye 1,000,000 Fry


Largemouth Bass 3,000 Small Fingerling

1941 Walleye 1,000,000 Fry


1942 Walleye 3,650 Small Fingerling


Northern Pike 200,000 Fry

1943 Walleye 1,000,000 Fry

Walleye 5,000 Small Fingerling


1944 Walleye 800,000 Fry




Smallmouth Bass 1,420 Small Fingerling

1945 Walleye 2,675,200 Fry



1946 Walleye 2,983,175 Fry



Smallmouth Bass 250 Small Fingerling

1947 Walleye 2,000,000 Fry



Largemouth Bass 250 Small Fingerling



Smallmouth Bass 10,000 Small Fingerling

1952 Walleye 27,345 Small Fingerling 1953 Walleye 9,627 Small Fingerling

Appendix Table 3 Continued.

Year Species Number Stocked Age/Size 1954 Walleye 8,400 Small Fingerling 1955 Walleye 1,260 Small Fingerling 1956 Walleye 8,400 Small Fingerling 1957 Walleye 8,400 Small Fingerling 1958 Walleye 2,800 Small Fingerling 1961 Walleye 30,500 Small Fingerling 1964 Walleye 25,000 Small Fingerling

Walleye 2,000 Large Fingerling

1967 Walleye 15,500 Small Fingerling 1976 Rainbow Trout 3,500 Yearling 1978 Rainbow Trout 3,500 Yearling 1979 Rainbow Trout 3,500 Yearling 1980 Walleye 1,300,000 Fry 1981 Walleye 62,494 Small Fingerling 1982 Walleye 19,800 Fry


Walleye 12,988 Large Fingerling


Rainbow Trout 7,652 Yearling

1985 Walleye 8,357 Small Fingerling 1987 Rainbow Trout 3,000 Yearling 1988 Walleye 49,731 Small Fingerling 1989 Walleye 5,800 Large Fingerling 1991 Walleye 22,541 Large Fingerling 1992 Walleye 70,793 Small Fingerling

Walleye 110,000 Fry


Walleye 950 Large Fingerling

1995 Walleye 4,984 Large Fingerling 1999 Walleye 200 Large Fingerling 2001 Walleye 2,000 Large Fingerling 2006 Walleye 474 Large Fingerling 2007 Walleye 2,581 Large Fingerling 2008 Walleye 6,150 Large Fingerling 2009 Walleye 7,661 Large Fingerling 2010 Walleye 11,028 Large Fingerling

Appendix Table 3 Continued.

Year Species Number Stocked Age/Size 2011 Walleye 16,534 Large Fingerling 2012 Walleye 8,582 Large Fingerling 2013 Walleye 11,615 Large Fingerling

lake owen walleye and bass update bayfield county, wi...lake owen is a low productivity lake that...

Documents