Muskellunge Population Characteristics and Angling Assessment in Pewaukee Lake, Wisconsin Susan Beyler & Robert C.

Transcription

1 Muskellunge Population Characteristics and Angling Assessment in Pewaukee Lake, Wisconsin Susan Beyler & Robert C. Anderson Susan Beyler, Wisconsin Department of Natural Resources, 141 NW Barstow St, Room 180, Waukesha WI 53188, Corresponding author: Robert C. Anderson, Wisconsin Lutheran College, 8800 W. Bluemound Rd., Milwaukee WI 53226, Key words: fisheries, lakes, tracking, creel, harvest, radio-telemetry

2 Synopsis A comprehensive fisheries survey, muskellunge mark and recapture population estimate and radio telemetry tracking study was conducted on Pewaukee Lake, Waukesha County Wisconsin during A May through November random stratified creel survey to assess game fish populations focusing primarily on muskellunge and comparing angling pressure, catch and harvest rates, and harvest characteristics was also conducted in We found an adult musky density of 1.28 per hectare, well above the average density of 0.81 per hectare found in a group of recently studied lakes in northern Wisconsin (Hanson 1993). Muskellunge in Pewaukee Lake have an above average growth rate and a mean length of approximately 84 cm for males and 94 cm for females. Based on radio telemetry tracking, Pewaukee lake muskellunge have a mean home range size of 34 ha in spring, 18 ha during summer and 21.6 ha in the fall. These home ranges overlapped each other extensively and included dense beds of native as well as exotic aquatic plant species. Female muskellunge had a mean home range of 63 ha while the males had a mean home range area of 17.2 ha. Muskellunge mainly used the shallow portions of the lake and daily movement was greater in the spring than summer and fall. Both catch rate and harvest rate declined between the 1982 and 1998 surveys, while angler hours directed at catching muskellunge nearly tripled. Mean length of harvested muskellunge increased 33 cm during that period. Management recommendations include continued stocking of muskellunge and development of a clear strategy toward either and action or a trophy muskellunge fishery in Pewaukee Lake.

3 Introduction Muskellunge populations in many North American lakes are typically managed by carefully balancing stocking density and harvest regulations (Simonson & Hewet 1999; Cornelius & Margenau1999). Adjustments of these management components are primarily based on estimates of post stocking mortality, population estimates of adult muskellunge, results of creel surveys, and angler surveys (Simonson & Hewet 1999; Margenau 1994; Hanson & Margenau 1992). Wahl (1999) expressed the importance of considering ecological factors that impact species distribution and abundance in developing strategies for fish introductions. This study in addition to comprehensive survey procedures, investigates muskellunge behavioral components such as home range size, movement patterns and habitat utilization in a stocked lake with no known natural reproduction of muskellunge. Pewaukee Lake is located in Waukesha County, Wisconsin. The lake has an area of hectares and consists of 20.6 km of shoreline. The lake is divided into two basins: the western basin and eastern basin. The western basin has a maximum depth of 45 feet and a mean depth of 15 feet, while the eastern basin has a maximum depth of eight feet. Most of the shoreline consists of gravel and sand sediment, while the vast majority (83%) of the lake bottom is muck (SEWRPC 2003) Pewaukee Lake contains a diverse fish community comprised of 45 species. Game fish include northern pike (Esox lucius), muskellunge (Esox masquinongy), largemouth bass (Micropterus salmoides), and walleye (Stizostedion vitreum vitreum). Pan fish such as bluegill (Lepomis macrochirus), yellow perch (Perca flavescens), and pumpkinseed (Lepomis gibbosus) are very abundant in the lake also. Varous species of fish have been stocked in Pewaukee Lake since the late 1800 s. The Wisconsin Department of Natural Resources has more recently stocked the Lake with walleye, northern pike, muskellunge, and largemouth bass. A muskellunge management program, consisting of stocking muskellunge and hybrid muskellunge, and subsequent creel census and surveys, was initiated during Since that time, the lake has been stocked annually, with the exception of 1974, 1978, and 1979, with fingerlings of either one or both of the above species. The program has generated a great deal of enthusiasm among anglers in Southeastern Wisconsin. A creel census conducted between 1973 and 1975 indicated a successful stocking program with a good muskellunge catch and excellent growth rates (SEWRPC 2003). This study will further evaluate the muskellunge fishery in Pewaukee Lake. Methods Fyke nets were set on Pewaukee Lake on March 2, From 12 to 20 nets were fished daily from March 2 through 10, and from March 23 through April 16. Cold weather caused refreezing of the lake from March 10 through 23, and the nets had to be removed during that time. Total effort was 388 net nights. Nets were moved, as needed, to locations throughout the lake in order to maximize catch. Locations used for fyke net sets are indicated on the lake survey map (Figure 1).

4 All muskellunge captured by fyke net were measured to the nearest centimeter, weighed to the nearest gram, sexed, and given a sex-differential fin clip (right-ventral for females, left-ventral for males, and upper-caudal for immature). All muskellunge over 50.8 cm in length were given an individually numbered aluminum strap tag, which was applied to the anterior edge of the dorsal fin base. Scale samples were collected from 10 muskellunge per 2.5 cm group, by sex, for aging. Muskellunge were then released, or transported to shore for radio tagging. From April 20 through April 29, 1998, we electrofished 7 nights on Pewaukee Lake. The entire shoreline was electrofished each night, utilizing 2 double-boom shocker boats with 2 dipnetters. Total effort was 49.3 hours of electrofishing, covering kilometers of shoreline. Muskellunge were measured, weighed, sexed, finclipped and tagged as above. Tag number of each recap was recorded to distinguish between fish marked from fyke nets and fish marked during electrofishing. Clipped muskellunge without a tag were re-tagged and counted as recaps. Radio transmitters were surgically implanted in the abdominal cavity of twenty muskellunge captured by fyke net or electroshocked. The fish were transported in live tanks to a central point on the lakeshore. A shielded needle technique (Ross & Kleiner 1982) was used to implant Advanced Telemetry Systems (ATS) transmitters in the abdomen of twenty muskellunge. The surgical procedure used was very similar to that described by Strand (1986). The fish were anesthetized prior to surgery with tricaine methanesulfonate (MS222) or CO 2. All study fish were released immediately after surgery at the same location near shore in the central section of the lake. In the process one muskellunge died and the transmitter was excised and implanted in another muskellunge. Transmitters were implanted in 15 male and 5 female muskellunge ranging from 72.4 to cm (Table 1). An additional nineteen Muskellunge were collected by hook and line during 1999 and 2000 (Table 2) and external ATS transmitters were attached at the base of the dorsal fin with plastic coated wire. External transmitter attachment was less stressful for the fish since it required no anesthetic and could be done immediately in the live well of the boat. These fish ranged from 81.3 to cm. and were released at the same location they were caught. The weight and sex of these fish were not determined. Transmitter fish were located with an ATS hand held directional loop antenna, a fourelement boat mounted Yagi antenna and a Challenger Model R2000 receiver. The whole lake was scanned by boat as often as weather and manpower permitted. The latitude and longitude of each location was determined using either a boat mounted Lowrance LMS 350A or hand held Eagle Expidition II global positioning system unit. At each contact point surface water temperature, total depth, secchi disk, substrate type and extent of vegetation were recorded. At some contact points dissolved oxygen, temperature at various depths, ph and conductivity were measured. Tracking was done during spring summer and fall with a few contacts made through the ice during winter. Musky

5 movements were plotted using Maptech Terrain Navigator software. Home range sizes were measured using the Maptech distance tool to enclose at least 95% of all contact points during the designated season. Daily movement was determined by measuring the distance between sequential contact points during the tracking season and dividing that distance by the number of days since the last contact. A Kruskal Wallis and Wilcoxon Signed Ranks tests were used to examine variation in movement and home range size between months and season. All statistical analyses were performed with the Statistical Package for the Social Sciences (SPSS 2002) and results were considered statistically significant at P-values less than A random, stratified creel survey was conducted from May 2 through November 30, The creel clerk monitored approximately 40 hours per week, including all weekends and holidays and 3 randomly selected weekdays. Morning or afternoon shifts were randomly selected. Each shift covered one-half of the available daylight hours. Each creel shift included 3 random instantaneous counts in which fishing boats and the number of boat and shoreline anglers were counted. For the remainder of the shift, the clerk interviewed angling parties, concentrating on anglers who had completed their fishing. Results Fyke Netting and Electrofishing We captured 233 male muskellunge and 90 female muskellunge during the fyke net survey (Table 3). Mean length of the male muskellunge was 85.6 cm; for females it was 94.0 cm. Mean weight was 4.45 kg. and 6.18 kg., respectively. Ninety-seven male muskellunge, 34 females, and 32 immature muskellunge were captured during two weeks of electrofishing in April. This does not include muskellunge that had been caught and marked in the fyke nets and recaptured by electrofishing. Mean length and weight of these muskellunge was nearly identical to that seen in the fyke nets (Table 4). Length of male muskellunge captured by fyke nets and electrofishing ranged from 61 to cm, with the mode at 81.3 cm (Figure 2). Forty-one percent of male muskellunge in our sample were over the minimum legal length of 86.4 cm. Female muskellunge ranged from 76.2 to cm in length, with the mode at 88.9 cm (Figure 3). Seventy-seven percent of female muskellunge captured by fyke net and electrofishing were over the 86.4 cm minimum length. During fyke netting, we marked 228 male muskellunge and 86 female muskellunge with finclips and dorsal fin tags. In our electrofishing survey we captured 150 males, of which 38 were marked from the fyke nets. Forty-seven females were captured, of which 10 were recaps from the fyke nets. We used the Peterson formula for population estimate, M C N =, where M is the number marked in the marking run, C is the total number R examined for marks in the recapture run, and R is the number of marked fish caught in the recapture run. Our estimate for male muskellunge is 900, with a 95 percent

6 confidence range of 655 to 1,276. Our female muskellunge population estimate is 404, with a 95 percent confidence range of 220 to 860. The total adult muskellunge population is estimated to be 1,304, or 1.3 per hectare. Applying the mean weight of male and female muskellunge to their population estimates results in an adult biomass of kg, or 6.43 kg of adult muskellunge per hectare. Applying the Peterson formula only to muskellunge measuring 83.8 cm in length or greater, we obtained an estimate of 468 male and 372 female muskellunge (840 total) which would be available for harvest during the upcoming muskellunge angling season. A minimal 2.5 cm of growth was allowed for recruitment into the vulnerable population between the spring survey and the angling season. No estimate of subadult population number or biomass was possible due to the low catch of subadults in both fyke netting and electrofishing. Radio Telemetry Home range size and and the distribution and movement of muskellunge is an important factor in understanding the impact of the density of muskellunge on Pewaukee Lake. During a total of 39 fish were tracked resulting in 1,987 contacts. Based on the tracking results of 25 of these fish and 1,644 contacts made during a mean home range size of 34 ha was determined for spring, 18 ha during summer and 21.6 ha in the fall (Table 5). Based on a Kruskal Wallis test this seasonal variation was not significant. Home ranges were distributed mainly in the shallow portions of the lake as exemplified by the 1998 results (Figures 4-7). These home ranges overlapped each other extensively and included dense beds of native as well as exotic aquatic plant species (Figures 8 & 9). Home ranges of individual muskellunge that were tracked extensively varied greatly in size and in seasonal variation (Tables 6-10). For example fish 531 roamed across most of the east basin of the lake during the spring with a mean home range of ha and during the summer settled in to a much smaller area (30.6 ha) while at the same time fish 561 had a smaller home range in spring (39.8 ha) than summer (60.0 ha). Other fish such as 551 maintained a very small home range through out the study ( ha) as it remained in a small heavily weeded bay along the northeast shore of the lake (Table 6). Home range size for female and male muskellunge were compared based on tracking data for two female fish (531 and 561) and four male fish (551, 600, 650 and 660). These fish were selected for the comparison because they provided the greatest number of determined home range measures and contacts (Tables 6 & 7). Four males were used in order to match the sample size of the female fish. A Wilcoxon Signed Ranks test revealed that female home range sizes were significantly larger than male home range area during The female muskellunge had a mean home range of 63 ha while the males had a mean home range area of 17.2 ha. It should also be noted that both the female fish were larger by over 2 kg than the male muskellunge. Daily movement of muskellunge was significantly greater in spring than summer and fall (Tables 11-13). A Kruskal Wallis test was used to compare daily movement for 1998

7 2001 between seasons. The spring mean of m was significantly greater than the summer mean (143.5 m) and fall mean (98.8 m). Summer and fall were not significantly different. Monthly means of daily movement (Table _) were compared using the same test and no significant difference was found. Daily movement was based on 1,449 measures of daily movement by 35 muskellunge during Muskellunge were aged using scales, and the mean length of each year class was calculated. Male muskellunge from age IV through age X were found. Female muskellunge ranged from age V to XI (Table 14). Pewaukee Lake muskellunge exhibit an excellent growth rate, both males and females being several centimeters longer than the average for muskellunge of the same age in Wisconsin lakes. Log 10 of the number of fish caught within each year class was plotted against age for male and female muskellunge, separately. The best-fit line of the descending limb was calculated. The resulting catch curves indicate an annual mortality rate of 46 percent for male muskellunge age VI through X (Figure 10) and annual mortality of 49 percent for females age V through XI (Figure 11). Creel Survey A random, stratified creel survey was conducted from May 2 through November 30, Three instantaneous counts were made on each census day; lake use counts were made concurrent with instantaneous counts. In between counts, the clerk conducted angling party interviews from completed angling trips. A similar study was done on Pewaukee Lake from May 1 through September 30, One of the objectives of this study was to look for changes in fishing pressure, catch and harvest rates between the 1982 and 1998 creel surveys. Fishing Pressure Fishing pressure was estimated from instantaneous counts. Total fishing pressure on Pewaukee Lake is estimated at 197,727 hours, or hours per hectare. Fishing pressure is above average compared to recent creel surveys on other Southeast Wisconsin lakes (Table 15). Interestingly, Pewaukee Lake s total pressure dropped 12 percent from that seen in the 1982 creel survey. The highest fishing pressure was seen in May, followed closely by July and June (Table 16). Total pressure over the entire season was split equally between weekdays and weekends/holidays, although pressure was slightly higher on weekends for all months except June and July. Fishing pressure was lowest in November. Fishing pressure in 1982 was weighted more toward weekdays; 56 percent of angling occurred on weekdays that year.

8 Boat angling accounted for 83 percent of total pressure; the remaining 17 percent was shore or pier angling. Most shore angling took place in May, June and July. In 1982, 26 percent of anglers fished from shore or piers. Directed Angling Effort During party interviews, anglers were asked which species they were fishing for. Some anglers indicated they fished for one species for part of their total angling time, then switched to another species. Other anglers indicated that they fished 100 percent of their time for two or more species (for example, they may cast for bass while still-fishing with a bobber for bluegills). In the former case, their total angling time would be apportioned according to the percentage of time fished for each species. In the latter case, their entire angling time would be applied toward each of the species fished for. These times were credited toward each species as part of its directed angling effort. For this reason, the total directed angling effort exceeds the total angler hours during the creel survey. In 1998, a total of 179,781 angling hours were directed toward catching game fish species. Muskellunge drew the most interest among anglers, with 47 percent of the total game fish effort (Figure 12) and more directed angling hours than any other species of fish. Largemouth and smallmouth bass followed muskellunge with 28 percent and 15 percent, respectively. Walleyes and northern pike drew comparatively little angler interest. Game fish angling in 1982 focused on largemouth bass, which accounted for nearly half of the total hours directed at catching game fish (Figure 13). Muskellunge took second place, with 33 percent. Muskellunge angler hours in 1982 were 57 percent lower than the 1998 directed pressure. Smallmouth bass, walleye and northern pike all accounted for a relatively small proportion of the total game fish angling hours. Catch and Harvest Estimates An estimated 179,096 fish were caught in Pewaukee Lake during the May through November season. Of these, 56,155 (31.4 percent) were harvested (Table 17). Anglers harvested 48 of the 840 legal muskellunge we estimated at the beginning of the angling season. This reflects a 6 percent harvest mortality. Total mortality was 46 to 49 percent. Therefore, the remaining 40 to 43 percent represents loss due to other causes, such as hooking mortality, disease, injury, predation, senescence, or emigration. The 1998 per hectare yield was much lower than in 1982, when an estimated 190,005 fish were harvested. Per hectare game fish yield was anywhere from 2 times (muskellunge and northern pike) to 40 times (smallmouth bass) higher in 1982 than in The decrease in the harvest may be due to more anglers practicing catch and release, rather than a reduction in the number of quality-sized fish.

9 Catch and Harvest Rates Catch and harvest rates, as fish per hour, are reported as overall and specific. Overall catch and harvest rates are fish caught or harvested per all angler hours combined, including incidental catch Specific catch and harvest rates are fish caught or harvested per angler hours directed at catching that species only. Generally, specific catch and harvest rates are higher than overall rates, and are a better indicator of angler success at catching a particular species. Catch rates for muskellunge, smallmouth bass and walleye were all lower in 1998 than in 1982 (Figure 14). Smallmouth bass catch rate dropped 87 percent, concurrent with the aforementioned nine-fold increase in directed angling effort. Muskellunge and walleye directed angling effort has also increased. Largemouth and northern pike catch rates were slightly higher than in Both, incidentally, saw a decline in directed angling effort between the two creel surveys. Harvest rates for all game fish species were lower in 1998 than in The most dramatic declines were seen in smallmouth, largemouth and walleye (Figure 15). Harvest Characteristics Table 18 summarizes the mean, maximum and minimum length of fish species observed in the harvest. Minimum length limits were in place for all game fish species in Muskellunge size limit was 86.4 cm, walleye minimum was 38.1 cm, largemouth and smallmouth bass had a 35.6 cm size limit, and northern pike minimum was 66 cm. In 1982, the minimum length for muskellunge was 76.2, and no other species had a size limit. Assuming that anglers harvest only legal fish, a size limit should reduce total harvest and harvest rates. The mean length of muskellunge in the 1998 harvest was cm (Figure 16). Muskellunge in the creel ranged from 92 to cm in length. In 1982, the average muskellunge harvested was only 75.4 cm long (Figure 17). The harvest ranged from 50.8 to cm in length. Summary and Discussion Our present comprehensive survey is the first such study done on Pewaukee Lake since 1982, and the first ever to quantitatively assess the Pewaukee Lake muskellunge population and evaluate their behavior. In recent years, Pewaukee Lake s muskellunge fishery has attained near-legendary status. Interest among local and regional anglers and the media has raised many unanswered questions about the size and health of the muskellunge population, whether the lake could be managed for trophy muskellunge fishing, and what impact a trophy muskellunge fishery might have on the entire

10 Pewaukee Lake fish community. The purpose of this study was to gather information needed to address these questions. Among the many things we have learned about the Pewaukee Lake muskellunge fishery: Pewaukee Lake has 1.28 adult muskellunge per hectare. In terms of biomass, there are 6.4 kg. of muskellunge per hectare. This compares favorably to other Wisconsin lakes managed for muskellunge. Hanson (1993) studied population density, size structure, angler use and exploitation on 9 Class A muskellunge lakes in northern Wisconsin. Adult muskellunge density averaged 0.81 per hectare, and ranged from 0.07 to 1.51 per hectare. Biomass of these 9 lakes ranged from 0.2 Kg. to 6.7 kg. per hectare, with an average of 4.0 kg per hectare. This puts Pewaukee Lake well within the above average range for both density and biomass. Muskellunge in Pewaukee Lake grow faster than the statewide average listed in the Wisconsin Department of Natural Resources Fish Management Reference Book. This is expected because the longer growing season and, generally, greater fertility in southern Wisconsin waters result in higher growth rates compared to those in northern Wisconsin where most muskellunge data has been collected. Due to faster growth, Pewaukee Lake muskellunge reach the minimum size limit 1 or 2 years earlier than those in most northern Wisconsin lakes. Natural reproduction does not appear to be a significant contributor to the Pewaukee muskellunge population. Potential spawning habitat is limited to two small areas of the lake. Pewaukee Lake, located in southeast Wisconsin, is outside the historic range for muskellunge. During spring, 1998 fyke netting a single 16.5 cm unclipped yearling was identified from the 1997 year class. All muskellunge stocked in 1997 had been finclipped; therefore, this fish was not stocked. However, this unclipped fish was well below the average of 30.5 to 33 cm for the clipped (stocked) yearlings seen in Pewaukee, and below the statewide range of 24.1 to 35.6 cm (mean, +/- 1 std. dev.) for age 1 muskellunge. It is possible that this fish was misidentified; nevertheless, a single yearling does not indicate more than a token wild muskellunge population derived from natural reproduction. More in-depth study is needed to answer the question of natural reproduction with any amount of certainty. Muskellunge tracking results indicate that the muskellunge population of Pewaukee lake is extensively distributed over areas of the lake that are shallow and well vegetated. The deeper parts of the lake are also known to contain muskellunge based on angler reports however the muskellunge tracked in this study did not utilize these areas extensively. Overlap in home range and extensive movement of muskellunge is consistent with population estimate which indicates each muskellunge has less than one hectare to itself. Seasonal mean home range sizes were smaller by a factor of 10 than those found in Leech Lake, Minnesota (Strand 1986) and slightly less than half the size of home ranges found in West Okoboji Lake, Iowa (Miller & Menzel 1986). Leech lake is 40 times larger than Pewaukee Lake and West Okoboji is 1.5 times larger. Pearson (Indiana Division of Fish

11 and Wildlife Project Report 2000) found similar size home ranges as those determined in this study in Webster Lake, Indiana which is one third the size of Pewaukee Lake. Pearson found home ranges to average 14 percent of the lake area whereas on Pewaukee Lake the average home range was 5 percent of the lake area. Similarly, Dombeck (1979) reported home ranges of 2.5 to 27.7 ha in Moose Lake, Sawyer County, Wisconsin which has a surface area of 676 ha while for 52 ha Black Lake Dombeck reported home ranges of Daily movement in Pewaukee lake did show a similar seasonal pattern to that seen in Okoboji Lake (Miller & Menzel 1986) and Moose and Black Lake, (Dombeck 1979) where activity was high in spring and dropped off through summer. Pewaukee lake muskellunge however did not show a significant increased activity in fall as seen in these previous studies. Angler interest directed toward muskellunge fishing has more than doubled since the 1982 creel survey. In 1998, more hours were spent fishing for muskellunge than any other species in Pewaukee Lake. That year, anglers spent 83.5 hours per hectare pursuing muskellunge compared to 35.6 hours per hectare in This is more than double the average of 37.8 hours per hectare of muskellunge angling seen in the aforementioned 9 northern Wisconsin lakes. On those lakes, muskellunge angling ranged from 9.9 to 72.2 hours per hectare in creel surveys conducted between 1979 and Creel surveys done on Bone Lake in 1982 and 1985 estimated muskellunge angling at 36.6 and 46.2 hours per hectare, respectively (Cornelius & Margenau 1999). Another study encompassing creel surveys conducted from 1990 through 1993 had an average directed angling effort of 48.2 hours per hectare (Simonson & Hewett 1999). It is clear that angling effort directed specifically at muskellunge in Pewaukee Lake is very high compared to Class A lakes elsewhere in the state. Pewaukee Lake s proximity to the metro Milwaukee and northern Illinois areas obviously makes it an attractive and convenient destination for muskellunge anglers. Both the catch rate and harvest rate for muskellunge dropped since The specific catch rate (muskellunge caught by anglers who were fishing for them) in 1982 was per hour. In 1998, it was per hour, a decline of 43 percent. Looking at paired creel censuses in Simonson & Hewett (1999) we see a 57 percent decrease in catch rate on Big McKensie Lake, a 22 percent decline on Sissabagama Lake, and a 38 percent decrease on Big Arbor Vitae Lake. Three other lakes, Sand, Big and Little Arbor Vitae had increases in catch rate of about the same magnitude. All 6 showed an increase in directed angling effort toward muskellunge between their earlier creel survey in and the later survey in All but one showed a concurrent drop in harvest rates ranging from 30 to 100 percent. The single exception was Sand Lake, where no change in harvest rate occurred. Pewaukee Lake s specific harvest rate dropped 70 percent, from per hour to muskellunge per hour. Although Pewaukee s 1998 harvest rate is 93 percent lower than the average of the lakes studied by Simonson and Hewett, the specific catch rate is only 19 percent lower than that seen in the creel surveys on those lakes. Again, the high rate of catch-and-release practiced in southeast Wisconsin undoubtedly contributes to the low harvest rate.

12 Consistent stocking, at a higher rate than was done prior to 1982, has not resulted in an increase in catch rate for muskellunge. Despite stocking, on average, 133 percent more muskellunge each year the catch rate declined 43 percent between 1982 and Since we have no 1982 muskellunge population estimate to compare to, we are unable to determine whether the additional stocking had a positive impact on the number of muskellunge available to anglers. Assuming stocking did not decrease the number of muskellunge, the declining catch rate must be related to the sharp increase in the number of anglers fishing for them. We cannot attribute lower catch rates simply to increased harvest, since both harvest rate and the estimated number of muskellunge harvested also declined. Perhaps, once caught, a muskellunge needs a certain amount of time to recover before biting again. Having been caught several times, a muskellunge may become smart and not bite as readily resulting in a lower catch rate. The average length of a harvested muskellunge increased between the 1982 and 1998 creel surveys. In fact, the maximum length of a harvested muskellunge in 1982 barely exceeded the length of the smallest muskellunge harvested in The mean increased 35.6 cm, from 76.2 to cm. In 1998 the smallest muskellunge harvested was 94 cm long. In 1982, a 50.8-cm muskellunge was observed in the creel. In 1998, only 1 muskellunge under cm in length (a 94-cm fish) was observed by the creel clerk. On average, each muskellunge in Pewaukee Lake was caught at least twice during the angling season. However, some were caught several times and some may have never been caught. One radio-tagged muskellunge was recorded caught 7 times during the season. During spring fyke netting and electrofishing, we observed muskellunge with jaws damaged from hooking. Also, we received numerous reports (probably due to the publicity the Pewaukee Lake muskellunge study was receiving) of dead muskellunge over the course of the angling season. These were both tagged and untagged fish, which probably succumbed to hooking mortality despite anglers best efforts at careful handling and immediate release. Pewaukee Lake loses some muskellunge to angling in spite of catch and release practices. The vast majority of muskellunge caught by anglers are released. The estimated harvest was less than 2 percent of the estimated number of muskellunge caught by anglers during the 1998 season, and only 5.7 percent of the population estimate of adult muskellunge over 83.8 cm long. Therefore, angler exploitation accounts for a very small proportion of the 46 to 49 percent total annual mortality of adult muskellunge. The majority of muskellunge mortality is from hooking or other injury, disease, predation, or emigration. Muskellunge leave Pewaukee Lake via the Pewaukee River in unknown numbers. Tagged muskellunge were recovered below the dam during the study, and muskellunge are observed congregating below the dam most springs. We recently received a report of a tagged muskellunge being caught on Tichigan Lake, in Racine County. This emigration undoubtedly plays a part in the non-harvest mortality rate of adult muskellunge seen in the catch curves.

13 With this information we can return to the original question of whether or not Pewaukee Lake can, or should, be managed for trophy-sized muskellunge. One question that arises during this discussion is, if Pewaukee Lake is capable of producing a state record-sized muskellunge, why don t we see any? Even though catch and release is the norm, the largest muskellunge on record coming from Pewaukee Lake is the kg (134.6 cm long) female taken by Joe Ehrhardt in November, That fish was estimated at 13 years old. With more than 20 years of active muskellunge management since then, we should have been able to produce at least one larger fish. Since so few muskellunge under cm long are harvested at this time, would placing a cm minimum size limit on them really result in more trophy-sized muskellunge? Do we have a defacto cm size limit already? Would we need to go to a higher size limit, perhaps 127 cm, to see an impact on the size structure of the muskellunge population? A very high size limit can have the effect of attracting more angling pressure from people seeking the new state record. This can result in higher angling mortality, as very large fish often need to be played for a longer time and are more exhausted when finally landed. What would be the effect on the forage base of producing more, larger top-line predators? A recent study on Bone Lake (Cornelius & Margenau 1999) showed that imposing a cm size limit increased muskellunge density five-fold, to nearly 2.5 per hectare, and increased mean length 15 percent. However, relative weight decreased across years and lengths during the 30-year study, suggesting intraspecific competition for food. Mean relative weight (Wr) of adult muskellunge declined 13 percent between 1964 and Mean relative weight, all years combined, declined from 108 for fish under 76.2 cm to 99 for fish 96.5 cm and longer. This suggests that larger muskellunge have a more difficult time finding adequate forage. It is now generally accepted that there are two types of muskellunge lakes; trophy lakes, which have low density, but produce very large muskellunge, and action lakes, which have higher densities, where you are more likely to catch a muskellunge, but tend not to produce very large fish. Based on Pewaukee Lake s muskellunge population and size structure, and angler success from the creel survey and from talking with anglers, I feel that Pewaukee Lake fits into the action category. Most managers would probably agree that managing one lake for both types of muskellunge fishery is difficult, if not impossible. Therefore, we must decide if we want to continue management as an action lake, or switch to trophy management. Acknowledgments Funding for this study was provided by the Milwaukee Chapter of Muskies Inc. Club member volunteers assisted with data collection in particular Ralph Anderson and Ron Groeschl. Student assistants critical to data collection were Tom Schlavinsky and Dave Kramer and for developing maps for the manuscript Abby Kroken.

14 References Cited Cornelius, R. R. & T. L. Margenau Effects of length limits on muskellunge in Bone Lake, Wisconsin. North American Journal of Fisheries Management 19: Dombeck, M.P Movement and behaviour of the muskellunge determined by radiotelemetry. Wisconsin. Department of Natural Resources Technical bulletin p Hanson, D.A The muskellunge fishery in nine northern Wisconsin lakes. Research Report 159, May Wisconsin Department of Natural Resources. Hanson, D.A. and Margenau, T.L Movement, habitat selection, behavior, and survival of stocked muskellunge. North American Journal of Fisheries Management 12: Margenau, T. L Evidence of homing of a displaced muskellunge, Esox masquinongy. Journal of Freshwater Ecology 9(3): Miller, M.L. and B.W. Menzel Movements, homing, and home range of muskellunge (Esox masquinongy) in West Okoboji, Iowa. Environmental Biology of Fishes 16: Ross, M.J. and C.F. Kleiner Shielded-needle technique for surgically implanting radio-frequency transmitters in fish. Progressive Fish Culturlist 44(1): SEWRPC (Southeastern Wisconsin Regional Planning Commission) A lake management plan for Pewaukee Lake Waukesha County, Wisconsin. Community planning assessment report no. 58, 2 nd edition, Madison, Wisconsin. Simonson, T. D. & S. W. Hewett Trends in Wisconsin s muskellunge fishery. North American Journal of Fisheries Management 19: SPSS SPSS, version SPSS, Chicago. Strand, R. F Identification of principal spawning areas and seasonal distribution and movements of muskellunge in Leech Lake, Minnesota. American Fisheries Society Special Publication 15: Wahl D. H An Ecological Context for Evaluating the Factors Influencing Muskellunge Stocking Success. North American Journal of Fisheries Management Volume 19(1):

15 Figure 1. Map of Pewaukee Lake, Waukesha County, Wisconsin with fyke net locations indicated by dots along the near shore regions of the lake.

16 60 50 Number Length (cm) Figure 2. Length frequency for male muskellunge captured by fyke net and electrofishing from Pewaukee Lake, Waukesha County, Wisconsin March 2 through April 29, 1998.

17 Number Length (cm) Figure 3. Length frequency for female muskellunge captured by fyke net and electrofishing from Pewaukee Lake, Waukesha County, Wisconsin March 2 through April 29, 1998.

18 Figure 4: Distribution of muskellunge home ranges in Pewaukee Lake, Waukesha County, Wisconsin during spring 1998.

19 Figure 5: Distribution of muskellunge home ranges in Pewaukee Lake, Waukesha County, Wisconsin during summer 1998.

20 Figure 6: Distribution of muskellunge home ranges in Pewaukee Lake, Waukesha County, Wisconsin during fall 1998.

21 Figure 7: Depth contours in Pewaukee Lake, Waukesha County, Wisconsin (SEWRPC 2003)

22 Figure 8: Distribution of native aquatic plants in Pewuakee Lake, Waukesha County, Wisconsin during July, 2000 (SEWRPC 2003).

23 Figure 9: Distribution of Eurasian water milfoil in Pewuakee Lake, Waukesha County, Wisconsin during July, 2000 (SEWRPC 2003).

24 Figure 10. Catch curve for male muskellunge age VI through X from Pewaukee Lake, Waukesha County, Wisconsin during 1998.

25 Figure 11. Catch curve for female muskellunge age V through XI from Pewaukee Lake, Waukesha County, Wisconsin during 1998.

26 Figure 12: Angler hours directed toward each game fish species on Pewaukee Lake, Waukesha County, Wisconsin during 1998.

27 Figure 13: Angler hours directed toward each game fish species on Pewaukee Lake, Waukesha County, Wisconsin during 1982.

28 Figure 14: Catch rates, as fish per hour, of game fish species in Pewaukee Lake, Waukesha County, Wisconsin from the 1982 and 1998 creel surveys..

29 Figure 15: Harvest rate, in fish per hour, of game fish species in Pewaukee Lake, Waukesha County, Wisconsin from the 1982 and 1998 creel surveys.

30 Figure 16: Maximum, minimum and mean length of the 1998 game fish harvest in Pewaukee Lake, Waukesha County, Wisconsin.

31 Figure 17: Maximum, minimum and mean length of the 1982 game fish harvest in Pewaukee Lake, Waukesha County, Wisconsin.

32 Table 1: Radio frequency, transmitter implantation date, final track date, number of contacts, total length, weight, and sex for muskellunge with surgically implanted radio transmitters in Pewaukee Lake, Waukesha County, Wisconsin. Radio Frequency Date Implanted Final Track Date Number of Contacts Total Length (cm) Weight (kg) Apr Dec F Apr Apr M Apr Apr M Apr Sep F Apr Oct F Apr Aug M Apr Oct F Apr Aug M Apr Jun M Apr Aug M Apr Oct M Apr-1998 none M Apr-1998 none M Apr Oct F Apr May M Apr Feb M Apr Jun M Apr Aug M Apr Oct M Apr Nov M Sex

33 Table 2: Radio frequency, transmitter implantation date, final track date, number of contacts, total length, for muskellunge with externally attached radio transmitters in Pewaukee Lake, Waukesha County, Wisconsin. Radio Frequency Date Implanted Final Track Date Number of Contacts Total Length (cm) Jun Oct Jun Nov Jul Nov Aug Nov Sep Sep Jul Oct Jun Oct Aug Jul Sep Aug Jul Aug Sep Jul Aug Jul Sep Jul Sep Jul Oct Jul Sep Dec Sep Oct Oct Jul Sep-2000 none

34 Table 3: Muskellunge captured by fyke net from Pewaukee Lake, Waukesha County, Wisconsin during March 2 through April 16, Total effort = 388 net nights. Catch/ Net Night Mean Length (cm) Std. Dev. (cm) Mean Weight (kg) Std. Dev. (kg)

35 Table 4. Muskellunge captured by electrofishing from Pewaukee Lake, April 20 through 29, Total effort = 49.3 hours of electrofishing; 134 km of shoreline shocked. Mean Catch per Catch per Mean Length Weight Sex Number km Hour (cm) Std. Dev. (kg) Std. Dev. Male Female Immature

36 Table 5: Muskellunge mean home range size, number of contacts and fish by season in Pewuakee Lake, Waukesha County, Wisconsin during Spring Summer Mean Home Range Number Number Mean Home Range Number Number Years (ha) SE of Contacts of Fish All Years (ha) SE of Contacts of Fish All Mean Home Range (ha) SE Years Fall Number of Contacts Number of Fish All

37 Table 6: Seasonal home range for individual muskellunge with internal transmitters across years ( ) on Pewaukee Lake, Waukesha County, Wisconsin. Number of home range determinations for each fish (N), total contacts within the range and sex of the fish are also included. Home Range Size (ha) Frequency Sex Spring Summer Fall Mean SE N Contacts Mean SE N Contacts Mean SE N Contacts 501 F F M F M M M F a F M M M M M

38 Table 7: Seasonal home range for individual muskellunge with external transmitters across years ( ) on Pewaukee Lake, Waukesha County, Wisconsin. Number of home range determinations for each fish (N) and total contacts within the range of the fish are also included. Home Range Size (ha) Frequency Spring Summer Fall Mean SE N Contacts Mean SE N Contacts Mean SE N Contacts

39 Table 8: Individual muskellunge home range area and associated contacts in Pewaukee Lake, Waukesha County, Wisconsin during spring Area Contacts Total Freq (ha) in range Contacts Area Contacts Total Freq (ha) in range Contacts Area Contacts Total Freq (ha) in range Contacts Area Contacts Total Freq (ha) in range Contacts

40 Table 9: Individual muskellunge home range area and associated contacts in Pewaukee Lake, Waukesha County, Wisconsin during summer Area Contacts Total Freq (ha) in range Contacts * Area Contacts Total Freq (ha) in range Contacts Area Contacts Total Freq (ha) in range Contacts Area Contacts Total Freq (ha) in range Contacts

41 Table 10: Individual muskellunge home range area and associated number of contacts in Pewaukee Lake, Waukesha County, Wisconsin during fall Area Contacts Total Freq (ha) in range Contacts Area Contacts Total Freq (ha) in range Contacts Area Contacts Total Freq (ha) in range Contacts Area Contacts Total Freq (ha) in range Contacts

42 Table 11: Mean daily muskellunge movement, standard error, number of contacts, and associated number of fish tracked by radio telemetry in Pewaukee Lake, Waukesha County, Wisconsin during April - July April May Distance (m) Number of Distance (m) Number of Mean SE Contacts Fish All Mean SE Contacts Fish All June July Distance (m) Number of Distance (m) Number of Mean SE Contacts Fish All Mean SE Contacts Fish All August September Distance (m) Number of Number of Distance (m) Number of Mean SE Contacts Fish All Mean SE Contacts Fish All

43 Table 12: Mean Monthly muskellunge movement, standard error, number of contacts, and associated number of fish tracked by radio telemetry in Pewaukee Lake, Waukesha County, Wisconsin during October December, October November Distance (m) Number of Distance (m) Number of Mean SE Contacts Fish All Mean SE Contacts Fish All December Distance (m) Number of Mean SE Contacts Fish All

44 Table 13: Mean Seasonal muskellunge movement, standard error, number of contacts, and associated number of fish tracked by radio telemetry in Pewaukee Lake, Waukesha County, Wisconsin during Distance (m) Spring Number of Number of Distance (m) Summer Number of Number of Mean SE Contacts Fish All Mean SE Contacts Fish All Fall Distance (m) Number of Number of Mean SE Contacts Fish All

45 Table 14. Age frequency and mean length at age for male and female muskellunge captured by fyke net and electrofishing from Pewaukee Lake, Waukesha County, Wisconsin March 2 April 29, Age Males Number Females Mean Length (cm) Age Number Mean Length (cm) IV IV V V VI VI VII VII VIII VIII IX IX 0 X X XI XI

46 Table 15. Estimated fishing pressure in hours per hectare on selected Southeast Wisconsin lakes. Data from random stratified open water creel surveys. Lake Survey Year Size (ha) Hours per hectare Pewaukee Lake Pewaukee Lake Oconomowoc Lake Lac La Belle Lac La Belle Golden Lake Golden Lake Nagawicka Lake Beulah Lake Rockland Lake Pretty Lake Brown s Lake Average 144.7