Comprehensive Fishery Survey of Lake Delton Sauk County, Wisconsin 2014

Comprehensive Fishery Survey of Lake Delton Sauk County, Wisconsin 2014.

Waterbody Identification Code: 1295400

Nathan Nye Senior Fisheries Biologist Wisconsin Department of Natural Resources Poynette, Wisconsin June 2017

Approvals

Tim Simonson-South District Fisheries Supervisor

David Rowe-Fitchburg Fisheries Team Supervisor

EXECUTIVE SUMMARY

A comprehensive fishery survey was conducted on Lake Delton during the spring of 2014, including early fyke netting for northern pike and walleyes (SN1), early electrofishing to recapture marked walleyes (SE1), late spring electrofishing for bass and panfish (SE2), and fall electrofishing. Black crappie was the most abundant of all sport fish species collected (panfish or gamefish) from Lake Delton. The SE2 catch rate of 121 fish/mile ranked in the 98th percentile statewide. The fyke net catch rate was 17.1 fish/net night during SN1. Black crappies in Lake Delton grow slower than region and state averages after age 3, and the disparity increases with age. Black crappies average 7.6 inches by age 4, 8.4 inches by age 5, and 8.6 inches by age 6. Black crappie PSD, PSD-9, and PSD-P values calculated from the SN1 catch were 77, 4, and zero, respectively. Values calculated from SE2 were 31, 1, and zero, respectively. Lake Delton produces large numbers of black crappies but there are few large fish. White crappies were present at low abundance and had slightly larger mean lengths at age than black crappies, averaging 8.5 inches at age 4 and 9.2 inches at age 5.

Walleye was the second most abundant sport fish species collected in the survey. The Chapman- modified Petersen PE was 0.4 adults ≥ 15 inches/acre, well below the desired 2 to 3 adults per acre in a stocked walleye fishery in Wisconsin. However, the overall walleye density is much higher when considering all sexually mature fish and immature fish ≥ 12 inches; the PE was 6.4 fish/acre. Large fingerling walleyes stocked by the Delton Sportsman’s Club are surviving and beginning to provide a walleye fishery in Lake Delton. Walleyes in Lake Delton grow slower than in other Sauk County Lakes, averaging 14.3 inches at age 4. Mean length at age values generally were near the state average. Single fish aged at 9 and 14 years were found, indicating that adult fish escape from Mirror Lake into Lake Delton. These fish would have entered Lake Delton following the breach and subsequent rotenone treatment. Also, 25% of walleyes tagged in Lake Delton and subsequently reported by anglers or collected in WDNR surveys were reported from Dell Creek or the Wisconsin River indicating that substantial walleye escapement from Lake Delton is occurring.

Bluegill was the third most abundant sport fish species collected, and most bluegills were collected during SN1. The SE2 catch rate of 18 fish/mile was low compared to other lakes statewide. Bluegill mean length at age was similar to the state averages. Bluegills average over 6 inches by age 4, and over 7 inches by age 7. The PSD, PSD-7, and PSD-P values calculated from the SN1 catch were 59, 5, and zero, respectively. High end size structure is poor even when the population is sampled with gear that selects for larger fish. Good bluegill habitat is lacking (shallow areas with aquatic vegetation), and improved habitat and water quality will be essential elements in the maintenance and improvement of the bluegill population.

Northern pike is the top predator species in Lake Delton, adult northern pike are common, and size structure is very good. The Schnabel PE in 2014 was 329 mature fish or 1.2 fish/acre, and the population is composed primarily of fish that passed downstream from Mirror Lake following the breach; only one stocking of northern pike (fry, 2013) has occurred since the breach. Fish as large as 41.1 inches were collected and 60% of northern pike were ≥ 26 inches (PSD-26 = 60). Northern pike growth in Lake Delton is faster now compared to before the breach, and is better than the state average. Both males and females reach legal harvest size around age 4.

The 2014 largemouth bass SE2 CPE8 and CPE12 values of 7.5 and 2.9 fish/mile ranked in the 17th and 29th percentiles, respectively. Largemouth bass were more readily collected in the fall, when the CPE8 and CPE12 values of 25.4 and 6.6 fish/mile ranked in the 42nd and 48th percentiles, respectively. Largemouth bass growth is good. The mean age of largemouth bass

measuring 14.0-14.9 inches was 4.9 years which compares very well with other lakes in Sauk and Columbia counties. Size structure continues to improve following the breach. The PSD, PSD-14, and PSD-P values calculated from the combined catches of SN1, SE1, and SE2 were 47, 16, and 8, respectively. The same values calculated from the fall electrofishing catch were 26, 8, and 3, respectively. These values should improve over time as the population continues to replenish itself and fish mature and begin to fill out older age classes.

Smallmouth bass were present at low abundance in the spring, with 38 individuals collected during SN1, SE1, and SE2 combined. Smallmouth bass were more readily collected in the fall when 105 were captured during fall electrofishing. Mean lengths of smallmouth bass collected in the spring and fall were 11.6 and 9.1 inches, respectively. Fish as large as 20.5 inches were collected, but the majority of the population is composed of fish from 2 to 4 years of age. This indicates natural reproduction is occurring and a respectable smallmouth bass fishery is starting to develop in Lake Delton. Growth is good, with smallmouth bass averaging 14.5 inches by age 5.

Other fish species of interest to anglers that were collected include yellow bass, yellow perch, pumpkinseed, bullheads, and white bass. These species add minor components to the overall sport fishery. Common carp is a detrimental rough fish species that is common in Lake Delton.

Lake & location Lake Delton, Sauk County T13N, R6E Sections 15, 16, 21

Physical/chemical attributes Morphometry: 249 acres, maximum depth of 16 feet, average depth of 8 feet, 6.79 miles of shoreline (Ball et al. 1971, Ives 1971) Watershed: 79.6 square miles (Ball et al. 1971). Lake type: Drainage, artificial impoundment of Dell Creek. Dam on Dell Creek holds a 20-foot head and has a top draw spillway, as well as bottom draw capability which is utilized during periods of high discharge on Dell Creek. Water Clarity: Turbid, but occasionally clear in fall. Littoral substrate: Sand Trophic status: Eutrophic Aquatic vegetation: Very limited Winterkill: Infrequent Boat Landings: There is one boat launch located in a bay on the south side of the lake at the intersection of Canyon Dr. and Adams St. The launch is paved, there is a boarding dock during the open water season, and there is parking available for 11-15 vehicle-trailer units. There are two additional smaller ramps located on the northwest end of the lake; one on Hiawatha Dr., and one on Clare Isle Dr. Other Features: There is good shore fishing access on the north end of the lake consisting of a free public fishing pier accessed from Dam Rd., and all along the shore in the area of the breach along County Highway A. Fish season and bag limit information for Lake Delton can be found in Table 1.

Purpose of survey Baseline lake survey Tier 1 assessment.

Dates of fieldwork Fyke netting survey conducted April 2 through April 23, 2014 (SN1). Electrofishing surveys conducted April 30, 2014 (SE1), May 20, 2014 (SE2), and September 29, 2014 (FE).

Fishery Black crappies and walleyes are abundant, but most of the walleye population is smaller than the minimum harvest size. Northern pike, bluegills, largemouth, and smallmouth bass are common. White crappies, yellow perch, and other panfish are present. Common carp and yellow bass are two abundant rough/non sport fish species.

BACKGROUND

Lake Delton is a 249 acre impoundment of Dell Creek in northeastern Sauk County, Wisconsin (actual surface area 249.23 acres, acreage per Wisconsin Register of Waterbodies 2015). It is formed by a dam built in 1927 that creates a 20 foot head, and the dam is located on Dell Creek approximately 0.25 mile upstream of its confluence with the Wisconsin River (Ball et al. 1971, Larson 1995). The maximum depth of the lake is 16 feet, and much of the shoreline around the lake is steeply sloped and heavily developed with numerous resort complexes and cottages lining the shoreline. Dense summer algal blooms have historically influenced summer water quality, often reducing water clarity to around two feet (Larson 1995). Although aquatic macrophytes have never been noted as abundant, routine herbicide treatments have been practiced since the late 1940s (Larson 1995).

Historic records show that from the early 1940s through the early 1960s, a variety of fish were stocked into Lake Delton, including largemouth bass, bluegill, yellow perch, white bass, black and white crappies, bullheads, northern pike, catfish, sturgeon, white sucker, gizzard shad, redhorse sucker, and walleye (Ives 1971). This wide variety of stocked species came from fish rescue operations by the rough fish station located at Wisconsin Dells. Intensive walleye stocking occurred from 1963 through 1969, and walleye stockings have occurred on a regular basis since that time which provided a good walleye fishery for anglers up until the breach and draining of the lake occurred during the flooding of June 2008.

Historically, fish surveys took place on Lake Delton with varying levels of effort. A large seine was pulled in 1957, fyke netting and fall boomshocking occurred in 1969, and fall boomshocking occurred from 1974-1976, in 1979, and from 1982-1984. These surveys indicated a good sport fishery in Lake Delton supported by panfish species including yellow and white bass and both crappie species, and to a lesser extent yellow perch and bluegills (Ives 1971, Larson 1995). Prominent gamefish species included largemouth bass, walleyes, and northern pike, while the forage community was abundant and dominated by gizzard shad, white suckers, golden shiners, and logperch (Larson 1995). Common carp were documented at low abundance with individuals attaining large sizes (Larson 1995). A comprehensive survey occurred in 1995 which included early and late spring fyke netting, early and late spring boomshocking, and fall boomshocking. The results of the 1995 survey supported findings of previous surveys, and this survey serves as the only relatively recent comprehensive survey of Lake Delton available from the time period prior to the 2008 breach. The presence of channel catfish in the catch during the 1995 survey led

to a 1996 survey that targeted channel catfish using baited hoop nets. The 1996 catfish survey documented a viable, naturally reproducing channel catfish population in Lake Delton, and it was noted that the catfish population may have begun in part from a 1990 stocking of catfish in Mirror Lake, immediately upstream of Lake Delton (Fuller 1997). Follow-up hoop net surveys were recommended to continue to assess the catfish population over time, but these surveys were never completed. Fall boomshocking surveys were conducted on a nearly annual basis from 1997 through 2005 as a means of evaluating success of walleye stockings. Likewise, electrofishing surveys were conducted at least once annually from 2009 through 2013 following the 2008 breach to track the recovery of the fish population.

Lake Delton was drawn down in the fall of 1982 to allow for installation of a sewer line, dam repair, and dredging of some of the bays on the lake to improve navigation (Larson 1995). The sewer line served the residents of the lake, who previously had been utilizing septic systems which were thought to contribute greatly to the nutrient load in the lake. However, by 1995 no improvement in water quality had been noted (Larson 1995). The lake is drawn down one foot annually during the winter to prevent damage to the shoreline from ice.

On June 9, 2008, approximately 12 inches of rain fell in the greater Lake Delton area on ground that was already saturated from previous rain events. The amount of water passing through the lake was so great that it was feared that the dam, 81 years old at the time, would fail so sandbagging efforts were concentrated around the dam. However, the water found a path of lesser resistance and a breach formed along the shoreline approximately 750 feet to the northwest of the dam structure. The seepage of water from the lake through the sandy soil weakened the strength of the ground, and the eroding action of water flowing over land and Highway A coupled with the unstable underlying soil eventually caused the ground to give way entirely and form a new drainage channel in the area where it was believed that Dell Creek entered the Wisconsin River prior to the last ice age. Lake Delton emptied through the breach into the Wisconsin River, taking part of the shoreline, three homes, and most of the fish in the lake with it. Two other homes were destroyed but were not washed away.

The lake remained empty throughout the summer of 2008 as County Highway A was rebuilt, the Lake Delton dam was repaired, and plans were made for a chemical treatment with rotenone to remove nuisance fish (carp and gizzard shad) from what little water remained over the lake bed. This included the flowing channel of Dell Creek, and several pockets of ponded water. The

rotenone treatment was performed by WDNR personnel and took place in the late fall of 2008, while the re-filling of the lake began in December. Re-stocking efforts began with plantings of forage fishes (fathead minnows, golden shiners, white suckers) in April and May of 2009. The first gamefish stocked were small fingerling walleyes in June. Channel catfish and smallmouth bass were stocked near the end of September, and bluegills and additional walleyes were stocked in early October of 2009. Additional stockings of various species have occurred annually since 2009. Stocking data for Lake Delton for the years 2009 through 2014 is summarized in Table 2.

METHODS

Data collection-spring netting and electrofishing

During ice-out, one standard 3-foot hoop fyke net with 0.7 inch bar, 1.4 inch stretch mesh was set on April 2, 2014 in the narrow, flowing portion of Lake Delton (Dell Creek) just upstream of the main lake. As ice-out progressed, additional nets were set until a total of 7 nets was reached on April 11 before being reduced to 5 nets on April 15. The fyke nets targeted northern pike and walleyes (SN1). Fyke net locations (GPS coordinates) can be found in Table 3. Nets were run six days a week through April 15 before being run every other day until fyke netting was completed on April 23.

Gamefish and panfish were measured to the nearest 0.1 inch and a subsample of each species was weighed using electronic scales. Panfish and small gamefish were weighed on a scale that held a maximum weight of 2 kilograms with a precision of 0.001 kg (one gram). Larger gamefish were weighed on a scale that held a maximum weight of 20 kg with a precision of 0.01 kg (10 grams). Both scales were manufactured by Yamato Corporation (model PPC-200W). Metric measurements were mathematically converted to pounds prior to data analysis. Aging structures were taken from a subsample of bluegills, black crappies, white crappies, largemouth bass, smallmouth bass, northern pike, walleyes, and yellow perch (Table 4). The goal was to take structures from 5 fish per half-inch group for bluegills, both crappie species, and both bass species, and 5 structures per half-inch group from each sex for northern pike, walleye, and yellow perch; sex was recorded when evident based on expression of eggs or milt.

All captured walleyes ≥ 12 inches and any sexually mature walleyes ≤ 12 inches were marked with a top caudal (TC) fin clip for the population estimate (PE). Immature walleyes ≤ 12 inches were marked with a bottom caudal (BC) fin clip. Additionally, walleyes ≥ 12 inches were

marked with Floy tags to help track fish movement between Lake Delton and the Wisconsin River, as well as harvest through angler reporting of tagged fish. Presence of tagged fish in future surveys will be used to further assess stocking success in terms of production of harvestable walleyes. Mature northern pike captured during fyke netting were marked with a top caudal fin clip for the purpose of calculating a population estimate, while immature fish were marked with a bottom caudal fin clip. All northern pike captured after the first lift day were examined for marks.

A WDNR standard direct current (DC) boom shocker boat was used to sample fish on Lake Delton during the spring and fall of 2014. The first electrofishing survey occurred on the night of April 30, 2014 (SE1) to recapture walleyes that were marked during SN1, and also to mark largemouth bass for a population estimate. The entire shoreline was sampled and all gamefish were collected and measured to the nearest 0.1 inch. Hard structures were removed and fish were weighed as needed to fill out length bins for age and growth analysis. Walleyes were examined for marks for calculation of the PE. Largemouth and smallmouth bass ≥ 8 inches were marked with a top caudal fin clip and those ≤ 8 inches were marked with a bottom caudal fin clip.

The second electrofishing survey occurred on May 20, 2014 (SE2). A total of two electrofishing stations were chosen, which encompassed the entire shoreline of the lake. The first station began with a randomly chosen start point and was 2 miles of shoreline in length. Within the station, panfish and gamefish were collected during the first 0.5 mile, while gamefish only were collected for the remaining 1.5 miles. The second station consisted of a 0.5 mile panfish and gamefish run with the remainder of the shoreline of the lake sampled as gamefish only (3.4 miles). Rough fish and other non-game fish were observed and counted while sampling all stations, but were not dip netted. All gamefish and panfish were measured to the nearest 0.1 inch. Aging structures were taken and weights were recorded from gamefish and panfish as necessary to fill out length bins. Starting and ending GPS coordinates for spring and fall electrofishing stations can be found in Table 5.

The fall electrofishing survey occurred on September 29, 2014. Two 2-mile stations were sampled, with all panfish and gamefish collected in the first 0.5 mile of each station, and gamefish only collected in the remaining 1.5 miles in each station. All gamefish and panfish were measured to the nearest 0.1 inch.

Data Analysis

The walleye PE (number of adult fish ≥ 15 inches) was calculated using the Chapman modification of the Petersen single-census method where fish are marked during multiple fyke netting events (SN1), followed by a single recapture event (SE1). The formula is noted here: (푀+1)(퐶+1) 푁 = − 1 푅+1 Where N is the estimated population size, M is the number of fish that were marked, C is the number of fish captured in the recapture survey and examined for marks, and R represents the number of fish captured in the recapture survey that had marks. Once the estimate was calculated, it was divided by the surface area of the lake to determine adult walleye density (number of fish ≥ 15 inches / acre). This density was then compared to average densities for stocked and naturally reproducing walleye fisheries in Wisconsin.

The largemouth bass PE would have been calculated using the same formula. However, too few bass were marked and recaptured during SE1 and SE2 to allow calculation of a meaningful population estimate.

A multiple census mark-recapture population estimate for northern pike was calculated using the Schnabel method. The formula for the Schnabel method is noted here: Σ(퐶 푀 ) 푁 = 푡 푡 푅+1

Where N is the population size, Ct is the number captured on day t, Mt is the number marked on day t, and R is the total number of recaptures from the survey (Ricker 1975).

For SN1, SE1, SE2, and fall electrofishing total catch and catch per unit of effort (CPE) was calculated by gear type for all species. Length frequency distributions were generated for species of interest including bluegill, black crappie, white crappie, largemouth bass, northern pike, walleye, white sucker, common carp, and yellow bass. Length range, mean length, median length, and mode length were calculated for all species. Proportional size distribution of quality (PSD) and preferred length fish (PSD-P) were calculated for all panfish and gamefish species with more than 100 individuals collected (Anderson and Neumann 1996, Guy et al. 2007). Length designations for stock, quality, preferred, memorable, and trophy sizes of the panfish and gamefish species collected from Lake Delton can be found in Table 6; these values were used for PSD calculations (Anderson and Neumann 1996, Guy et al. 2007). For bluegills, PSD calculations were made from the fyke net catch as well as from the fall electrofishing catch.

Possible bias toward larger fish exists for the fyke net data because fyke nets have been shown to be selective for larger bluegills (Laarman and Ryckman 1982). Too few bluegills were collected during SE2 for meaningful PSD calculations. Size-specific CPE (fish per mile ≥ x inches) is another metric for analyzing size structure that may be used when sample sizes are too small for meaningful PSD calculations. However, size-specific CPE was not reported for bluegills here.

Aging structures (scales, dorsal spines, and anal fin rays/spines) were used to estimate ages of a subsample of each species, and age and size data of these fish were used to generate age-length keys to estimate the age frequency of the population as a whole based on the aged subsample. Age frequency distributions were then generated for each species. The mean age at 14.0-14.9 inches (MAL14) is a metric sometimes used to compare growth in largemouth bass populations in Wisconsin, and this metric was calculated for largemouth bass from Lake Delton and compared to the MAL14 values for several other lakes in Columbia and Sauk counties that have been surveyed since 2006.

Once age frequency distributions were completed for each species, inferences were made about year class strength and mortality when possible. Mean length at age was used to make inferences about growth of fish in Lake Delton by comparing the lake to regional and statewide averages. Mean length at age was calculated using methods outlined in Bettoli and Miranda (2001), with the formula listed here:

퐿푖 = (∑ 푁푖푗푙푖푗)/푁푖

푛푖푗 Where 퐿푖 represents the mean length of the ith age group, 푁푖푗 = 푁푗( ) , 푁푗 is the number of fish 푛푗 in the jth length group, 푛푖푗 = number of fish of the ith age group subsampled in the jth length group, 푛푗 is the number of fish subsampled in the jth length group, and 푁푖 = ∑ 푁푖푗 over all j length groups. The inputs to this equation are derived from the length frequency distribution of the sample and the age-length key. The midpoints of each length group were used for the values of푙푖푗.

Relative weights were calculated to evaluate body condition of fish. Relative weight (Wr) is a tool that compares the length of the fish to an expected weight for that length. Standard weights were calculated for individuals of each species that had weights recorded and standard weights were only calculated for individuals larger than the minimum recommended length for each species (Murphy et al. 1991, Anderson and Neumann 1996). Relative weights for each fish were

calculated by dividing a fish’s actual weight by the standard weight for a fish of that length. Average relative weight was then calculated for each species, and was done for each sex separately when sex data were available. Relative weight values between 75 and 100 indicate normal weight for a given length. A relative weight value greater than 100 indicates that a fish is in excellent condition. A relative weight value less than 75 indicates that a fish is in poor condition.

RESULTS AND DISCUSSION

General fish community

A total of 7,489 fish representing 17 different species from 6 families was sampled during spring netting and electrofishing, and fall electrofishing on Lake Delton during 2014. Catch by gear type for each period of sampling effort is shown for each species collected in Table 7.

Black crappie

In total, 1,613 black crappies were collected during the spring; overall catch rates were 17.1 fish/net night during fyke netting and 121.0 fish/mile of shoreline during SE2, placing Lake Delton in the 98th percentile in a statewide comparison of WDNR electrofishing survey catch rates on Wisconsin lakes (Table 7). An additional 48 crappies were collected during fall electrofishing; the catch rate was 43.6 fish/mile (Table 7). Black crappies were the most abundant sport fish (panfish or gamefish) in the survey.

Spring black crappie lengths ranged from 5.8 to 9.4 inches (n = 635), and the average, median, and mode lengths were 8.1 inches, 8.3, and 8.5 inches, respectively (Table 8). The length frequency distribution is represented in Figure 1. Of the black crappies ≥ 5 inches in length (stock size), fish ≥ 8 inches were present in good numbers (PSD = 68), but fish ≥ 9 inches were rare (PSD-9 = 4), and fish ≥ 10 inches were not present (PSD-P = 0). Fall black crappie lengths ranged from 2.7 to 10.2 inches (Table 8, Figure 2). Of the 48 black crappies collected in the fall survey 35% (n = 17) ranged in length from 2.7 to 4.0 inches, representing YOY produced in 2014.

Ages were estimated from scales for a subsample of 41 black crappies collected during SN1 and SE2, and these fish were also weighed. The most common age class in the sample was age 5 (44%), followed by age 6 (26%) (Figure 3). Ages 5 and 6 represented fish that would have

hatched in 2008 and 2009 in either Mirror Lake or Lake Blass and passed downstream into Lake Delton sometime during 2009 while the lake was refilling. The fall 2009 electrofishing survey occurred on September 23. Black crappies ranging from 3.8 to 5.0 inches were collected (n = 44, 58.7 fish/mile). Because no crappies were stocked in Lake Delton, these were fish that came downstream from Mirror Lake or possibly Lake Blass and would have included age 0+ and age 1+ fish at the time (fish with 1 or 2 summer growing seasons).

Interestingly, a record of a black crappie stocking in Lake Delton on September 28, 2009 exists in the WDNR stocking database with the total number of fish stocked entered as zero. It was later determined that although a permit was issued for stocking black crappies purchased from a private vendor, the crappie stocking never took place and a zero was entered in order to “close out” the permit that had been issued. Crappies found in 2009 and subsequent surveys were produced naturally in the other impoundments in the Dell Creek system and entered Lake Delton via escapement from these impoundments.

The large cohorts of age 5 and age 6 black crappies found in the 2014 survey appeared initially in the 2009 survey. This distinct group of fish was noted in subsequent electrofishing surveys in 2010, 2011, and 2012. Black crappie length frequencies from these surveys illustrated the growth progression of a distinct group of black crappies that ultimately became the large group of fish between 8.0 and 9.5 inches noted in the 2014 survey (Table 9).

In 2014, age 4 black crappies averaged 7.6 inches, age 5 fish averaged 8.4 inches, and age 6 fish averaged 8.6 inches (Figure 4). Black crappie growth in Lake Delton was similar to the state average through age 3, and below the region and state averages for ages 4 through 6, and the disparity increases with age (Figure 4). This indicates that suitable food sources exist in Lake Delton to sustain growth of small crappies, but the lake lacks the forage base necessary to sustain good crappie growth at later life stages. Black crappie mean length at age was significantly lower in 2014 than in 1995, when the only comparable pre-breach comprehensive survey was conducted on Lake Delton. All other sampling efforts that occurred between 1995 and the breach in 2008 focused on gamefish only. When comparing the results of the two surveys, black crappies were of similar size at age 2, but by age 3 the 1995 fish were 1.2 inches longer than the 2014 fish on average, and by age 4 the gap widens to 2.2 inches (Figure 5). This trend continues and the growth gap widens with increasing age through the last age class collected, which was age 6 in both surveys (Figure 5).

In 2014, black crappies were generally in good condition, with relative weights averaging 98.6 (n = 37) and no fish had a relative weight below 75 which would indicate poor body condition. However, relative weight showed a weak negative correlation with fish length; longer fish had lower relative weight values than shorter fish (Figure 6). This lends further support to the assertion that appropriately sized forage is lacking for larger, older black crappies.

Walleye

In total, 588 walleyes were collected from Lake Delton during the spring (including recaptures); catch rates were 2.9 fish/net night during SN1, 39.6 fish/mile of shoreline sampled during SE1, and 17.6 fish/mile during SE2 (Table 7). Walleye was the second most abundant sport fish species by number collected during the survey (Table 7).

For the population estimate, a total of 36 adult walleyes ≥ 15 inches was marked during fyke netting. Five adult walleyes were captured during SE1, and a mark was found on one of those fish. The Chapman modified Petersen population estimate was calculated at 110 adult walleyes ≥ 15 inches (95% CI 47 – 216), for a density of 0.4 adults ≥ 15 inches per surface acre (95% CI = 0.2 - 0.9 fish/acre).

When the PE was expanded to include all sexually mature fish regardless of size, a total of 152 walleyes was marked, 23 were captured during SE1, and marks were found on 6 of those fish. The PE was calculated at 524 sexually mature walleyes (95% CI 302 - 1,094), for a density of 2.1 fish/acre (95% CI 1.2 – 4.4 fish/acre).

When accounting for all sexually mature walleyes plus immature/unknown walleyes ≥ 12 inches, 226 walleyes were marked, 91 were captured during SE1, and marks were found on 12 of those fish. The PE was calculated at 1,606 walleyes (95% CI 997 – 2,831), for a density of 6.4 per acre (95% CI 4.0 – 11.4 fish/acre). Walleye PE data for all three scenarios can be found in Table 10.

In total, 548 walleyes were measured during spring sampling (total catch excluding recaptures) and lengths ranged from 4.4 to 26.5 inches (Table 11, Figure 7). A clear break in the length frequency distribution between the 8.5 and 10.0 half-inch groups was used to differentiate age 1 walleyes from the rest of the population (Figure 7). Aging structures were taken from fish ≥ 10

inches, almost entirely during SN1. Fish ≤ 10 inches did not appear in the sample until SE1. When considering the walleye population as a whole and not accounting for sex, walleye ages ranged from 1 to 14 years (n = 548), with age 3 being the most common (40%), followed by age 1 (37%), age 4 (15%), and age 5 (4%) (Figure 8). Mean lengths at age were similar to, and occasionally greater than the state average but less than the region average (Figure 9). The exception was age 1, when walleyes in Lake Delton were smaller than both the state and region averages. Walleyes reached the minimum harvest size of 15 inches as early as age 3, but did not average over 15 inches until age 5. Walleyes averaged 13.2 inches at age 3, 14.3 inches at age 4, and 18.0 inches at age 5 (Figure 9). Single fish were aged at 9 years (22.9 inches) and 14 years (26.5 inches) (Figure 9).

When accounting for sex, a total of 144 male walleyes was collected during SN1 and SE1, and lengths ranged from 11.1 to 18.8 inches, averaging 13.6 inches (Table 11). Ages of male walleyes ranged from 2 to 6 years, with age 3 being the most common (52%), followed by age 4 (38%), and age 5 (6%) (Figure 10). Male walleyes in Lake Delton reach the minimum harvest size of 15 inches as early as age 4, and average over 15 inches by age 5. Male walleyes averaged 11.9 inches at age 2, 13.0 inches at age 3, 14.1 inches at age 4, 17.0 inches at age 5, and the single age 6 male walleye collected measured 18.2 inches (Figure 11). Mean lengths at age of male walleyes observed in 2014 were markedly lower than those observed in 1995 (Figure 12).

A total of 22 female walleyes was collected during SN1 and SE1, and lengths ranged from 13.5 to 26.5 inches, averaging 18.6 inches (Table 11). Ages of female walleyes ranged from 3 to 14 years, with age 5 being the most common (37%), followed by age 4 (21%), and ages 3 and 6 (16%) (Figure 10). Female walleyes in Lake Delton reach the minimum harvest size of 15 inches as early as age 3, and average over 15 inches by age 4. Female walleyes averaged 14.8 inches at age 3, 17.1 inches at age 4, 18.9 inches at age 5, and 22.4 inches at age 6 (Figure 13). Single fish were aged at 9 years (22.9 inches) and 14 years (26.5 inches) (Figure 13). The mean length of age 3 female walleyes was 1.3 inches less in 2014 compared to 1995 (Figure 14). However, the mean lengths at ages 4 and 5 were very similar when comparing 2014 to 1995 (Figure 14). Female walleye growth in Lake Delton post-breach is similar to what it was pre-breach.

In total, 140 walleyes were collected from Lake Delton during the fall electrofishing survey and the overall catch rate was 34.1 fish/mile (Table 7). The CPE10 and CPE15 values were 13.9 and 1.2 fish/mile, respectively (Table 12). The CPE15 from the fall survey ranked in the 26th

percentile statewide. Lengths ranged from 4.0 to 17.5 inches, and the mean and median lengths were 9.1 and 8.5 inches, respectively. The catch was primarily composed of fish ≤ 12 inches, representing fish ages 0 through 2 (Figure 15). Only 5 fish ≥ 15 inches were collected.

Condition of walleyes captured in the spring in Lake Delton was average to good based on relative weights (Figure 16). Overall, walleye relative weight averaged 87.4 (n = 101). Females averaged 89.9 (n = 21), males averaged 85.9 (n = 51), and unknown sex fish averaged 88.1 (n = 29). Only two fish, a 12.5 inch male and a 16.1 inch female, had relative weight values below 75.

In total, 813 walleyes ≥ 10 inches were tagged during spring and fall surveys from 2011 through 2014. Of these, 92 were recaptured at some later date; 63 were recaptured by anglers and 29 were recaptured in WDNR fishery surveys. Recapture totals exclude fish that were tagged and recaptured by WDNR in the same waterbody during the same survey (e.g. tagged and recaptured during 2014 SN1). In total, 69 walleyes were recaptured in Lake Delton (75% of recaptures), and 23 were recaptured outside of Lake Delton in Dell Creek or the Wisconsin River (25% of recaptures). Escaped fish were caught and reported outside of Lake Delton as early as 7 days post-tagging. Twenty-nine tagged sublegal walleyes (≤ 15 inches) were reported by anglers as being caught in Lake Delton. Fourteen tagged walleyes ≥ 15 inches were reported by anglers as being caught in Lake Delton, harvest status was known for 12 of the fish, 9 were harvested (75%), and three were released. Legal-sized walleyes caught in Lake Delton are likely to be harvested. However, slow growth and escapement via the dam are limiting the number of fish that reach 15 inches while residing in Lake Delton.

Bluegill

In total, 571 bluegills were collected during the spring; the catch rates were 6.4 fish/net night during SN1 and 18.0 fish/mile of shoreline during SE2 (Table 7). The SE2 catch rate placed Lake Delton in the 16th percentile in a statewide comparison of WDNR electrofishing survey catch rates on Wisconsin lakes; judging purely by this metric bluegills are scarce in Lake Delton relative to other lakes in Wisconsin. Electrofishing catch rates of bluegill are highly variable, but appear to be lower overall following the breach (Table 13). However, pre-breach data are based on a very small sample size and include only two spring electrofishing surveys and a single fall electrofishing survey in 1995.

In terms of the total number of fish caught during the spring survey, bluegill was the third most abundant sport fish species collected (Table 7). All bluegills collected during SN1, SE2, and fall electrofishing were measured. Lengths of bluegills collected during fyke netting ranged from 3.1 to 7.7 inches, and the mean, median, and mode lengths were 6.0, 6.1, and 6.4 inches, respectively (Table 8). The length frequency distribution is represented in Figure 17. Bluegill PSD, PSD-7 and PSD-P values calculated from the SN1 catch were 59, 5, and zero, respectively (Table 8). Eighteen bluegills were collected during SE2 sampling, ranging from 4.6 to 7.0 inches. The mean, median, and mode lengths were 5.8, 5.8, and 4.6 inches, respectively Table 8.

In total, 126 bluegills were collected during fall electrofishing; the catch rate was 114.5 fish/mile which ranked in the 59th percentile statewide (Table 7). The fall bluegill CPE compared much more favorably on a statewide basis than the SE2 CPE. Lengths ranged from 1.7 to 7.6 inches, and the mean, median, and mode length values were 5.6, 5.7, and 6.5 inches, respectively (Table 8). The length frequency distribution from the fall electrofishing sample is represented in Figure 18. The PSD, PSD-7, and PSD-P values calculated from the fall electrofishing catch were 45, 7, and zero, respectively (Table 8).

Aging structures were taken from a subsample of 42 bluegills with lengths covering the 3.0 through 7.5 half-inch groups, and weights were recorded for these fish. All bluegill aging structures were taken during SN1. Bluegill ages ranged from 2 to 7 years, with age 4 fish being the most common in the distribution (Figure 19). Bluegill growth in Lake Delton appears to be moderate at best. Bluegills in Lake Delton grow slower than the region average, and very close to the State average throughout life. Bluegills reach an average length of 5.0 inches by age 3, 6.1 inches by age 4, and 6.5 inches by age 5 (Figure 20). Bluegill mean length at ages 2 and 3 was larger in 2014 than in 1995, and length at age 4 was nearly equal in the two surveys (Figure 21). For ages 5 through 7, however, mean lengths at age were larger in 1995 than in 2014 (Figure 21). In 2014, bluegills larger than 3 inches were in good condition with a mean relative weight of 94.0 (n = 41) (Figure 22).

Northern pike

In total, 401 northern pike were collected during the spring (including recaptures); the catch rates were 4.4 fish/net night during SN1, 2.4 fish/mile during SE1, and 0.8 fish/mile during SE2 (Table 7). The total catch excluding recaptures was 250 fish (242 fyke net, 8 electrofishing). The

Schnabel population estimate was 329 sexually mature northern pike, or 1.2 fish/acre (95% CI 279 - 387 total, or 1.0 - 1.5 fish/acre). Ice-free areas created by the flowing water from Dell Creek allowed the survey to begin when the lake was still ˃ 95% ice covered. Consequently, the survey was able to capture the entire northern pike spawning period. A single northern pike measuring 24.0 inches was collected in the fall electrofishing survey.

Overall, lengths of northern pike collected in fyke nets ranged from 11.8 to 41.1 inches, averaging 27.7 inches (Table 11). The length frequency distribution of sexually mature northern pike collected during SN1 is represented in Figure 23. The sex ratio for known-sex fish was 2.7:1.0, males to females. Mature males as small as 17.2 inches were present in the fyke net sample and males ranged up to 34.6 inches, averaging 26.3 inches (Table 11). Mature female northern pike ranged from 18.9 to 41.1 inches, and averaged 31.7 inches (Table 11). A single immature fish measured 11.8 inches; all other northern pike collected during SN1 were sexually mature. Sex could not be determined for northern pike collected during SE1 and SE2, and these fish ranged from 21.7 to 36.1 inches, averaging 27.4 inches (Table 11). Median and mode values for all sexes and sampling periods can also be found in (Table 11). Overall, size structure was very good based on stock density indices; PSD, PSD-26, PSD-P, and PSD-M values were 91, 60, 46, and 14, respectively.

Overall, northern pike ages ranged from 3 to 7 years and age 5 was the most common, composing 65% of the SN1 sample. Age 4 was the next most common at 22% followed by age 3 (7%), age 6 (5%), and age 7 (1%). The age frequency distribution is represented in Figure 24. Overall, northern pike averaged 21.8 inches at age 3, 23.8 inches at age 4, 29.9 inches at age 5, 27.2 inches at age 6, and the single age 7 fish measured 26.7 inches (Figure 25). Based on mean length at age values, northern pike appear to grow near the region average for ages 3 and 4, above the region average for age 5, just above the state average for age 6, and below the region and state averages for age 7. However, comparisons for age 7 fish are of little value because there was only one age 7 fish collected, a female. Also, all age 6 fish were males which accounts for the apparent decline in mean length at age from age 5 to age 6.

When considered separately, females ranged from 3 to 7 years, with age 5 being the most common, followed by age 4 (Figure 26). No age 6 females were collected. Female northern pike grow fast, reaching the minimum harvest size of 26 inches as early as age 4, and averaging 33.8 inches at age 5 (Figure 27). Female northern pike in Lake Delton are growing faster post-breach

than they did pre-breach. The mean length of age 3 females was nearly 2 inches larger, and at age 5 was 4 inches larger in 2014 compared to 1995 (Figure 28).

Males ranged from 3 to 6 years, with age 5 being the most common, followed by age 4 (Figure 26). Males reach the minimum harvest size as early as age 4, and averaged 28.0 inches at age 5 (Figure 29). Male northern pike growth in Lake Delton post-breach is slower than pre-breach for ages 3 and 4, but age 5 fish are larger post-breach than pre-breach (Figure 30). There were no age 6 pre-breach fish for comparison to those collected in 2014.

Condition of northern pike was average to good. Relative weights for northern pike were generally lower for males which averaged 90.0 (n = 128), females averaged 105.0 (n = 63), and the average for all northern pike combined including unknown sex fish was 95.0 (n = 192). Only 4 male fish had relative weights below 75, indicating poor body condition (Figure 31). Relative weight showed a weak positive correlation with fish length; longer fish had higher relative weight values. Additionally the relationship was slightly stronger for males than for females. This indicates that growing conditions improve as the fish get larger and can consume larger prey, in this case medium to large sized white suckers which are abundant in Lake Delton.

Largemouth bass

In total, 133 largemouth bass were collected during the spring; overall catch rates were 0.3 fish/net night during fyke netting, 9.4 fish/mile of shoreline during SE1, and 8.3 fish/mile during SE2 (Table 7). The catch rate of fish ≥ 8 inches (stock size) during SE2 was 7.5 fish/mile, and this ranked in the 17th percentile in a comparison of four southern Wisconsin drainage basins (Table 14). The catch rate of fish ≥ 12 inches during SE2 was 2.9 fish/mile, and this ranked in the 29th percentile in a comparison of four southern Wisconsin drainage basins (Table 14). This indicates that based on SE2 CPE8 and CPE12, largemouth bass abundance in Lake Delton is lower than the desired 20 to 30 fish/mile, and also low relative to other southern Wisconsin lakes. During the fall survey, 105 largemouth bass were collected and the catch rate was 25.6 fish/mile (Table 7). The CPE8 and CPE12 values from the fall survey were 25.4 and 6.6, respectively, ranking in the 42nd and 48th percentiles (Table 14).

A total of 82 largemouth bass was marked during SN1 and SE1, and 49 largemouth bass were collected during SE2. However, only three of the largemouth bass collected during SE2 were

found to have marks. Due to the low number of recaptured fish, a meaningful PE could not be calculated for largemouth bass.

Largemouth bass lengths from fish collected in the spring ranged from 6.8 to 18.3 inches, and the mean, median, and mode lengths were 11.6 inches, 11.7, and 11.7 inches, respectively (Table 11). The length frequency distribution is represented in Figure 32. Of the largemouth bass ≥ 8 inches in length (stock size), fish ≥ 12 inches were present in moderate proportion (PSD = 47), while fish ≥ 14 inches were less common (PSD-14 = 16), as were fish ≥ 15 inches (PSD-P = 8) (Table 11). Largemouth bass collected during the fall survey ranged from 3.0 to 17.7 inches, and the mean, median, and mode values were 11.3, 11.0, and 10.3 inches, respectively (Table 11). The length frequency distribution from the fall survey is represented in Figure 33.

Altogether, 83 largemouth bass were included in the age analysis. Age 3 was the most common age in the sample (43%), followed by age 2 (31%), and age 5 (11%) (Figure 34). Largemouth bass growth in Lake Delton is good based on mean length at age values. Largemouth bass generally grow faster than the state average and very near the region average for ages 2 through 4, between the state and region averages for ages 5 and 6 (Figure 35). The mean length of the single age 7 fish collected was larger than the state and region averages (Figure 35). Largemouth bass begin to reach legal harvest size (14 inches) as early as age 4, and by age 5 they average 14.4 inches. The average age of fish that measured 14.0-14.9 inches (MAL14) was 4.9 years; this is very good based on a comparison of 10 different lakes (11 total surveys) surveyed in Columbia and Sauk counties since 2006 (Table 15). Only Lake Wisconsin has shown faster growth of largemouth bass. Largemouth bass appear to be growing faster post-breach; lengths were greater for ages 2 through 7 in 2014 compared to 1995 (Figure 36). Condition of largemouth bass in Lake Delton in 2014 was good; relative weights averaged 105.2 (n = 40). No fish had a relative weight below 75, and 73% of weighed fish had relative weights greater than 100. There was a weak positive correlation between relative weight and fish length; larger largemouth bass were in better condition relative to smaller largemouth bass. Relative weights for largemouth bass in Lake Delton are represented in Figure 37.

Smallmouth bass

In total, 38 smallmouth bass were collected during the spring; overall catch rates were 0.1 fish/net night during fyke netting, 2.5 fish/mile of shoreline during SE1, and 3.1 fish/mile during SE2

(Table 7). The catch rate of fish ≥ 7 inches (stock size) during SE2 was 2.9 fish/mile, and this ranked in the 60th percentile statewide (Table 16). The catch rate of fish ≥ 12 inches during SE2 was 1.0 fish/mile, and this ranked in the 37th percentile statewide. This indicates that based on SE2 CPE7 and CPE12, smallmouth bass are common in Lake Delton. The number of 7 to 12 inch smallmouth bass compares favorably on a statewide level, but large fish are less abundant.

During the fall survey, 105 smallmouth bass were collected and the catch rate was 25.6 fish/mile (Table 7). The CPE7 and CPE12 values from the fall survey were 22.4 and 1.5, respectively, ranking in the 95th and 48th percentiles statewide (Table 16). This supports the assertion that fish measuring 7 to 12 inches are common, but larger fish are less abundant. The length frequency distribution for the spring and fall surveys combined is represented in Figure 38.

Altogether, 34 smallmouth bass collected during the spring were included in the age analysis. Fish ages ranged from 2 to 5 years, and a single age 9 fish was captured as well. Age 4 was the most common age in the sample (34%), followed by age 3 (31%), age 2 (25%), and age 5 (8%) (Figure 39). Smallmouth bass growth in Lake Delton is good based on mean lengths at age. Smallmouth bass in Lake Delton grow faster than the state average and very near the region average for ages 2 through 5, and the single age 9 fish was larger than the state and region averages (Figure 40). Smallmouth bass begin to reach legal harvest size (14 inches) as early as age 4, and by age 5 they averaged 14.5 inches (Figure 40). Fast growth of smallmouth bass in Lake Delton is likely a function of low to moderate densities of fish combined with an environment nearly devoid of cover for prey. Smallmouth bass in Lake Delton were in good condition, with an average relative weight value of 93 (n = 30). No smallmouth bass had a relative weight value below 75, and there was no correlation between relative weight and fish length (Figure 41).

The low CPE12 value in the fall 2014 survey indicates that the catch is mostly composed of smaller fish, and the fish that were initially stocked are reproducing successfully. Size structure should continue to improve with time.

White crappie

In total, 104 white crappies were collected during the survey and all were collected during SN1 and SE2. The catch rates were 1.1 fish/net night during SN1 and 7.0 fish/mile of shoreline during

SE2 (Table 7). Lengths ranged from 6.8 to 10.0 inches, and the average, median, and mode lengths were 8.7, 8.8, and 8.9 inches, respectively (Table 8). The length frequency distribution is represented in Figure 42.

Ages were estimated from scales for a subsample of 30 white crappies collected and 29 were weighed. Ages 2 through 5 were present in the sample. The most common age class in the sample was age 5 (40%), followed by age 3 (22%), age 2 (21%) and age 4 (17%), and the age frequency distribution is represented in Figure 43. White crappies averaged 8.0 inches at age 2, 8.5 inches at ages 3 and 4, and 9.2 inches at age 5 (Figure 44). White Crappie mean length at age in Lake Delton is about the same as the state average at age 2 and less than the state average for ages 3 through 5 (Figure 44). In 1995, lengths of white crappie ranged from 4.6 to 12.8 inches, and ages ranged from 1 to 5 years. Mean length at age in 1995 was similar to 2014 for ages 2 and 3, but much better for age 4 and 5 fish in 1995 compared to 2014 (Figure 45). In 2014, white crappies were generally in good condition, with relative weights averaging 97.6, and no fish had a relative weight below 75 (Figure 46). However, relative weight showed a weak negative correlation with fish length; longer fish had lower relative weight values than shorter fish (Figure 46). This would suggest that appropriately sized forage is lacking for larger, older white crappies.

Yellow perch

In total, 32 yellow perch were collected in the spring survey; catch rates were 0.4 fish/net night during SN1 and 1.0 fish/mile of shoreline during SE2 (Table 7). Yellow perch was the eighth most abundant sport fish by number collected during spring netting and electrofishing (Table 7). Overall, lengths of yellow perch captured during SN1 ranged from 5.3 to 8.5 inches, and the average, median, and mode lengths were 6.8, 6.8, and 6.7 inches, respectively (Table 8). Sex was known for 31 fish and the sex ratio of these fish was 0.8:1.0, males to females; the sample was nearly balanced between sexes. Male yellow perch ranged from 5.3 to 7.4 inches and averaged 6.1 inches. Female yellow perch ranged from 6.2 to 8.5 inches, and averaged 7.1 inches. The length frequency distribution is represented in Figure 47.

Age 3 and age 4 yellow perch were collected in the survey, with age 4 being the most common (57%); the age frequency distribution is represented in Figure 48. Overall, yellow perch growth was just above the state average, with fish reaching an average length of 6.3 inches at age 3 and 7.1 inches at age 4 (Figure 49). Females were larger than males, averaging 6.8 inches at age 3

and 7.4 inches at age 4, while males averaged 5.9 inches at age 3 and 6.8 inches at age 4. This is expected because males mature at younger ages and attain smaller size over their lifetime than females (Becker 1983). Yellow perch mean length at ages 3 and 4 was similar when comparing pre-breach (1995) to post-breach (2014) data (Figure 50). Yellow perch were in good condition based on relative weights. Males averaged 90.0 (n = 9) and females averaged 98.9 (n = 16), and only one fish had a relative weight below 75 (Figure 51). There was no correlation between relative weight and fish length.

Other desirable fish species

White suckers were the most abundant species collected during the survey. In total, 2,092 white suckers were collected during SN1, for a catch rate of 24.0 fish/net night (Table 7). A subsample of 220 white suckers was measured, and lengths ranged from 12.7 to 17.6 inches, averaging 14.8 inches. No small white suckers were collected or observed during the survey. The length frequency distribution is represented in Figure 52. White suckers provide an abundant forage base for the larger northern pike in the lake, indicated by the positive relationship between northern pike length and relative weight. The larger the pike grow, the larger size of white sucker they can consume. White suckers also undoubtedly provide forage for panfish and smaller gamefish via their fry. Pumpkinseed and white bass are two species that provide additional minor fishing opportunities in Lake Delton. White bass were present at low abundance prior to the breach, and only a single individual was collected in 2014.

Detrimental rough fish

Common carp were likely eliminated from Lake Delton by the rotenone treatment that occurred in December 2008 prior to the lake being re-filled. Dead carp were noted in treated areas within a few hours of application of the chemical. However, 15 carp were collected in the fall 2009 electrofishing survey (CPE = 18.8 fish/mile). These were small fish that ranged from 7.7 to 11.8 inches, averaging 10.1 inches. No large adults were collected. These fish likely represented a new year class of carp that entered Lake Delton from other connected waters. Carp have not been noted in past surveys of Lake Blass and the status of common carp in that waterbody is currently unknown. Common carp are present in Mirror Lake, and also in a pond located on the east side of East Hiawatha Drive that is connected to Lake Delton, and these waterbodies were not treated with rotenone in 2008. These waterbodies served as a source of new carp for Lake Delton, and a

relative lack of gamefish and centrarchid panfish in Lake Delton during most of 2009 allowed the carp to produce a successful year class.

Common carp was the third most abundant species collected overall in Lake Delton in 2014; 204 were captured during SN1 and 540 were observed during SE2 and fall electrofishing (Table 7). However, the number observed during SE2 in 2014 may be an error; the counting device used to tally the observed carp more than likely was not re-set between two of the stations (author’s recollection). Seventy-two common carp were measured during SN1, lengths ranged from 14.3 to 21.9 inches, and the mean and median values were 18.1 and 17.9 inches, respectively. The length frequency distribution is represented in Figure 53. Current population densities of gamefish and centrarchid panfish may be high enough to limit successful carp reproduction from now forward, but those larger individuals that already exist in the lake will continue to aid in the re-suspension of phosphorous for years to come. Carp removal by commercial seining operations is one avenue that may be explored for reducing carp numbers in Lake Delton in the future.

Gizzard shad were present in Lake Delton prior to the breach, but none were found in 2014, or in any other post-breach survey. The rotenone treatment was successful at eliminating them from Lake Delton, and there are no other source waters for shad further up in the Dell Creek watershed that could have fish move downstream to establish a population in Lake Delton.

Yellow bass were present in Lake Delton prior to the breach, and have been found consistently in surveys following the breach as well. There may have been individuals that survived the rotenone treatment, but perhaps more likely is that fish have passed downstream from Mirror Lake, which holds a very small source population, into Lake Delton. Yellow bass have not been noted in past surveys of Lake Blass, and their status in the private pond on Hiawatha Drive is unknown. In total, 326 of the 345 yellow bass captured in 2014 were measured, and the length frequency is represented in Figure 54. The yellow bass pulled off a successful year class in 2014, indicated by the group of 3.0 to 3.9 inch fish in the fall electrofishing sample (Figure 54). They also appear to have produced a good year class in 2012, indicated by the large group of fish between 6.0 and 7.4 inches in the SE2 sample (Figure 54). These estimates are derived from the length frequency distribution from the 2014 survey, and by using yellow bass age and growth data from Lake Poygan for comparison (Priegel 1975). Yellow bass can be a detriment to the fish community when introduced to small systems because they can be so prolific, and because they

cause a drain on the food base in the lake via their consumption of zooplankton, macroinvertebrates, and small prey fish.

CONCLUSIONS AND RECOMMENDATIONS

Fish escapement from impoundments connected to Lake Delton (Mirror Lake, Lake Blass) has contributed significant numbers of black crappies, northern, pike, and largemouth bass, and lesser numbers of smallmouth bass, white crappies, bluegills, and walleyes to the lake since the 2008 breach. These additions have supplemented stocked populations (walleyes, both bass species, bluegills), as well as created populations entirely from scratch (black crappies, northern pike, white crappies). Escapement has also allowed large numbers of stocked walleyes to escape Lake Delton into lower Dell Creek and the Wisconsin River, hampering efforts to restore the walleye fishery in Lake Delton to levels observed prior to the breach.

Walleyes (mostly extended growth fingerlings) have been stocked regularly in Lake Delton following the breach, often at higher densities and more frequently than State guidance recommends. These stockings have created an abundant but slow growing walleye population with few large adult fish. High walleye and crappie densities have created competition for forage that has caused both walleye and crappie growth rates to be slow. Walleyes generally are not reaching legal harvest size in Lake Delton until age 5. Tag returns indicate that escapement of walleyes ≥ 11 inches may be as high as 25%. Walleyes ≤ 11 inches have not been part of the tagging and movement study, so there is currently no way to estimate escapement of these fish from Lake Delton. Walleyes most often escape from Lake Delton before reaching legal harvest size. Based on information gathered from tagged fish reported by anglers it is very possible that more fish are leaving Lake Delton via the dam than are leaving via the angler’s creel. Escapement and slow growth are two major obstacles to building a good walleye fishery in Lake Delton. A recent study of walleye escapement from an Iowa reservoir found that escapement increased with increasing daily discharge, and decreased as fish length increased (Weber et al. 2013). Similarly, most escapement of walleyes in Lake Delton is occurring in fish between 11 and 15 inches in length, and significant escapement occurs in the early spring when discharge is likely to be higher.

The management goal for walleyes in Lake Delton is to return the fishery to levels seen in the years prior to the breach. The objective is to maintain a density of adult walleyes ≥ 15 inches of at least 2.0 fish/acre as estimated in the spring via the Chapman modification of the Petersen

single-census method. The recommended strategy to use to reach the goal is to stock 10 large fingerling walleyes per acre, every other year. Stocking at a higher density or more frequently than every other year should be avoided in an effort to reduce overall walleye densities and improve growth rates through reduced competition for forage. This will in turn lead to higher abundance of harvestable walleyes in Lake Delton.

Future comprehensive surveys should monitor walleye population density and growth rates to inform decisions about future walleye stocking rates. Because a comprehensive survey will only occur once every 10 years, mark-recapture population estimates may not occur with enough frequency to satisfy the manager’s information needs. A size-specific catch rate during a fall electrofishing survey (CPE15) could be used as an index of abundance that could be compared to pre-breach data to determine if the walleye fishery is nearing recovery to previous levels. The Mississippi Headwaters strain is the correct genetic strain of walleye that should be stocked in Lake Delton. Tagging of walleyes should continue in future surveys, primarily as a means of assessing escapement of walleyes from Lake Delton.

Tag return data also provides important information about angler harvest, and in cases where fish are marked and recaptured by WDNR, valuable growth data are obtained as well. Reducing stocking and population density and improving growth rates as a means of increasing the abundance of adult walleyes in Lake Delton is preferable to a regulation change to a higher minimum length limit and reduced bag limit at this time. Changing to a higher minimum length limit and reduced bag limit such as an 18/3 scenario may not produce the desired result of improved population size and age structure because slow growth and high escapement could combine to undercut the regulation. Only 5 years have elapsed since re-stocking began and insufficient data exist on the amount of time it takes a walleye to reach 18 inches in Lake Delton (sample size too small). Currently it takes 5 years for the average walleye to reach 15 inches in Lake Delton and it may take up to 7 years for some fish to reach 18 inches while in the meantime these fish face a good possibility of escaping the lake via the dam. In an 18/3 scenario anglers could essentially be waiting for adult fish that are never going to materialize. Walleye length at age beyond age 5, escapement rates, and angler preferences need to be better quantified and addressed if possible (operation of the dam) before meaningful discussions regarding the need for a regulation change take place.

Black crappies are currently present at a high density in Lake Delton and growth is poor. The higher density of black crappies, along with differences in the forage base account for poor black crappie growth in the years following the breach compared to the period before the breach occurred. Black crappie catch rates (fish/hour) in four spring electrofishing surveys following the breach averaged 224 fish/hour which was 6.4 times greater than two spring electrofishing surveys in 1995 that averaged 35 fish/hour (Table 9). Fish per hour was the metric chosen for this comparison because the distance of the shoreline shocked in the 1995 surveys was not recorded, but shocker “on time” was recorded. With the relatively high number of fish and correspondingly slow growth rates following the renovation and restocking of Lake Delton, the lack of crappies larger than 10 inches in the catch is not surprising. The fall 2014 electrofishing sample indicated that a small number of crappies have reached the 10 inch mark. The presence of YOY crappies in the fall 2014 sample indicates that some successful natural reproduction is occurring.

The high density of black crappies in the early post-breach years is not likely to persist. Crappies are not typically long-lived, and the bulk of the current population is age 5 or 6. Angler harvest and natural mortality will reduce numbers of these fish over the next few years. Future large year classes in Mirror Lake may contribute significantly to the Lake Delton population via escapement. However, future year classes of black crappies will face predation pressure from walleyes, northern pike, and largemouth bass that early post-breach year classes of crappies did not face, and this will help to temper crappie densities moving forward. Reduced crappie densities in the future should help alleviate pressure on the forage base in Lake Delton, benefiting all of the piscivorous fishes in the lake.

The age 5 white crappies found in Lake Delton 2014 most likely originated from a source population in Mirror Lake and entered Lake Delton by means of escapement through the Timme Mill Dam. White crappie mortality is often significant after age 5, which would help explain the absence of age 6 or older fish in 2014 (Becker 1983). Fish that were age 3 in 2014 represent the first year class that could have been produced in Lake Delton by fish that were age 5 in 2014, and this would have occurred in 2011. The age 2 fish collected in 2014 would have been produced by fish that were age 4 and age 5 in 2014, and these fish would have been age 2 and age 3 fish in 2012. Continued escapement of white crappies from Mirror Lake will likely continue to supplement the Lake Delton population moving forward.

White crappies were present in Lake Delton prior to the breach at somewhat higher abundance than in 2014. During the 1995 survey, a total of 95 white crappies was sampled during early spring fyke netting, and the catch rate was 5.3 fish/net night which is nearly 5 times greater than the 1.1 fish/net night in 2014. In 1995, lengths ranged from 4.6 to 12.8 inches, and ages ranged from 1 to 5 years. Overall, white crappie growth was better pre-breach (1995) compared to post- breach, particularly for older age classes based on mean length at age values. The difference in growth of older crappie age classes prior to the breach can be attributed to a much lower crappie density (both crappie species) overall in 1995, and differences in the type and amount of available forage before and after the breach. At any rate, white crappies add a nice element of variety to the panfish fishery in Lake Delton.

Northern pike provide a nice fishery for anglers in Lake Delton. Growth is good, and large individuals are common. Natural reproduction appears to be very low at best, and this is due primarily to a lack of suitable spawning habitat. Northern pike were not stocked in the years immediately following the re-filling of Lake Delton after the 2008 breach. A single stocking of northern pike fry occurred in 2013, and early indications are that these fish did not survive. The current northern pike population consists primarily of fish that were naturally produced in Mirror Lake, and then escaped Mirror Lake via the Timme Mill Dam before ending up in Lake Delton.

Northern pike older than age 6 were almost entirely absent from Lake Delton in 2014, and age 5 was by far the dominant year class. This indicates that a very large year class of northern pike was produced in Mirror Lake in 2009 and many of those fish now reside in Lake Delton. The absence of older fish in Lake Delton indicates that the northern pike that escape Mirror Lake primarily do so in their first few years of life, and escapement of older northern pike is not occurring (northern pike up to age 12 are present in Mirror Lake). The northern pike that escaped Mirror Lake in 2009 or shortly thereafter arrived in Lake Delton to find abundant forage, particularly white suckers and golden shiners, which had been stocked when the lake was re- filled. Abundant forage which was appropriately sized for consumption by young northern pike, combined with a lack of cover for prey fish, allowed the northern pike to be highly efficient predators. Northern pike growth, particularly among fish aged at 5 years in 2014, was excellent and a few fish were able to exceed 40 inches by age 5. The fact that age 5 female northern pike ranged from 18.9 inches up to 41.1 inches, and age 5 males ranged from 21.7 to 34.6 inches indicates that these fish grow at different rates, but probably also that they left Mirror Lake at different points in their life. Those that left closer to 2009 enjoyed a longer period of abundant

consumable forage in Lake Delton, and thus attained larger sizes than those that left Mirror Lake at later points in their first 5 years of life.

The management goal for northern pike in Lake Delton is to maintain a quality alternative to the bass/panfish/walleye portion of the fishery for anglers. The objective is an adult population (sexually mature fish) ≥ 1.0 fish/acre, with a PSD between 30 and 60, and an PSD-26 ≥ 40. The PSD objective is in line with the recommended range for a balanced population proposed by Willis et al. (1993). Natural reproduction in Mirror Lake coupled with escapement of these fish into Lake Delton should mitigate for the lack of natural reproduction within Lake Delton itself, providing enough individuals to sustain the adult population. However, future growth of northern pike in Lake Delton is not likely to remain at levels exhibited by the fish that inhabited the lake immediately following the breach. The potential of the fishery to produce trophy northern pike over 40 inches is not likely to last. While large forage (adult white suckers) remains abundant, smaller northern pike cannot utilize these fish as prey and will face a lack of smaller forage moving forward. Young northern pike will find themselves in competition with walleyes, crappies, and bass for small to medium sized forage fishes, which already appear to be scarce based on slow growth rates of walleyes and crappies found in this survey.

Bluegill electrofishing catch rates are highly variable, but appear to be lower overall following the breach (Table 16). However, pre-breach data are based on a very small sample size; only two spring electrofishing surveys and a single fall electrofishing survey in 1995. It is very difficult to assess bluegill stocking success and compare growth rates to pre-breach conditions because of a number of confounding factors. The fall 2009 electrofishing survey, which occurred prior to the first panfish stocking after the breach, found a single 8.1 inch bluegill. This indicated that fish were entering Lake Delton from either Mirror Lake or Lake Blass, though probably in limited numbers. After the breach, bluegill stocking occurred from 2009 through 2011, and in 2013, with multiple size classes of fish stocked (Table 2). Stocking records indicate that the 40,000 bluegills stocked in 2013 averaged 2 inches, but in reality may have ranged from 4 to 6 inches (Gordon Priegel personal communication). These fish lived large portions of their lives in a different body of water under different (and possibly ideal) growing conditions, and this may be why lengths at ages 2 and 3 were higher in 2014 compared to 1995. Stocked fish may have come from a variety of age classes, and by the time fish that escaped into Lake Delton from Mirror Lake and Blass Lake are considered, the clear interpretation of the population age structure is nearly impossible.

Lake Delton is nearly devoid of aquatic vegetation, and this is likely to impact bluegills negatively in the future. There is little suitable cover for young bluegills, and zooplankton grazing opportunities for bluegills will be reduced from what they would be in a system with more submersed aquatic vegetation. Bluegill recruitment is likely to be low, and growth rates may remain relatively slow. Bluegill growth can be negatively impacted by competition for food (zooplankton) between larval and juvenile bluegills and YOY gizzard shad (DeVries and Stein 1992, Dettmers and Stein 1992, Aday et al. 2003). This competition can lead to reduced growth rates and condition of bluegill throughout life (Aday et al. 2003). Gizzard shad were present in Lake Delton prior to the breach. However, the absence of gizzard shad from the fish community of Lake Delton post-breach should positively impact bluegill growth.

The management goal for bluegills is to maintain a balanced population capable of serving as a forage base for the largemouth bass in the lake, while providing an opportunity for anglers. The objective is to maintain a SE2 or fall electrofishing catch rate of ≥100 fish/mile for stock size fish (≥ 3 inches), with a PSD between 20 and 60, and an PSD-P between 5 and 20. These objectives follow ranges proposed by Willis et al. (1993) for a balanced bluegill population. The CPE and PSD objectives are currently being met, but the PSD-P objective is not. However, the state average for bluegill growth is 8 inches in 8 years, and at the time of this survey only 5 years had elapsed since the refilling of the lake began. The top end of the bluegill size structure should improve somewhat with the passage of more time. No regulation change is currently recommended. Bluegill stockings provided for by the Village of Lake Delton have occurred periodically following the breach, but improvements to bluegill habitat (aquatic vegetation) and water quality should be explored as alternatives to stocking for the long-term maintenance of a healthy, balanced bluegill population in Lake Delton.

Overall, mean largemouth bass catch rates post-breach are similar to the pre-breach period, and growth appears to be very good. The waters with the fastest growing populations of largemouth bass in Columbia and Sauk counties have low density bass populations with abundant gizzard shad as the main forage fish. Lake Delton has a low to moderate density bass population with no gizzard shad present; bluegills and black crappies are likely the primary prey of largemouth bass in Lake Delton. Fast growth of largemouth bass in Lake Delton is likely a function of low to moderate bass densities combined with an environment nearly devoid of cover for prey fish; largemouth bass are able to forage efficiently. It is possible, however, that our method of aging dorsal spine sections from bass ˃ 8 inches (scales are used for fish ≤ 8 inches) caused us to

underestimate the ages of fish ≥ 3 years old by one year due to the eroded central lumen often found in dorsal spines of bass. If true, this would mean that largemouth bass in Lake Delton are not growing quite as fast as the data from this survey would suggest.

The average largemouth bass catch rates for two spring surveys prior to the breach were higher than the average catch rates from six spring surveys that occurred after the breach, and this was true for all size classes (Table 12). The average CPE for seven fall surveys prior to the breach is nearly identical to the average CPE for four fall surveys that occurred after the breach (Table 12). However for size classes of fish ≥ 8 inches, catch rates are much lower in post-breach surveys (Table 12). The fall 2009 survey influences the data heavily. The 2009 survey occurred prior to the first stocking of largemouth bass after the breach, the catch rate was 98.7 fish/mile (74 fish, 0.8 miles), and the fish ranged from 3.8 to 7.9 inches (Table 12). These fish passed downstream from Mirror Lake into Lake Delton, and based on ages of largemouth bass in Mirror Lake in 2014, the largemouth bass found in Lake Delton in 2009 would have been age 1 and age 2 fish.

This indicates that largemouth bass stocking efforts and natural reproduction are supplemented, possibly on a large scale, by escapement from Mirror Lake and Lake Blass. A record of a largemouth bass stocking in Lake Delton on September 28, 2009 exists in the WDNR stocking database with the total number of fish stocked entered as zero. It was later determined that although a permit was issued for stocking largemouth bass purchased from a private vendor, the stocking never took place and a zero was entered in order to “close out” the permit that had been issued. This means that a single post-breach stocking of largemouth bass occurred in 2010 (large fingerlings from WDNR West-Central Region rearing ponds). This fact, coupled with evidence of significant bass escapement from Mirror Lake and potential natural reproduction in Lake Delton makes it likely that stocking played only a minor role in the re-establishment of largemouth bass in Lake Delton.

Spring largemouth bass catch rates have dropped off sharply in Lake Delton after 2011, and the SE2 catch rate of 8.3 fish/mile in 2014 was the lowest observed in Lake Delton since 1998 (Table 12). Because of the fact that in 2014, 74% of the population was composed of age 2 and age 3 fish and these fish are still not even close to legal harvest size, harvest is not a likely cause for the decline. The oldest fish in the lake are only just now reaching legal harvest size, and population size structure will continue to improve with time.

Escapement may be negatively impacting the largemouth bass population in Lake Delton. Lewis et al. (1968) documented major losses of largemouth bass from an artificial impoundment in southern Illinois that discharged via a spillway. Losses occurred during two major precipitation events in April and May and it was estimated that 31% of the original population of largemouth bass in the lake was lost in a single spring season (Lewis et al. 1968). Major precipitation events later in the summer did not cause escapement to occur. Largemouth bass escape from an impoundment immediately upstream of Lake Delton (Mirror Lake) via a spillway, so there is no reason to believe that these fish could not escape via the Delton Dam into lower Dell Creek and the Wisconsin River, especially considering that during high flow events Lake Delton discharges via both a spillway and a bottom draw system.

Prior to the breach, the mean smallmouth bass catch rates from two spring and six fall surveys from 1998 through 2005 were nearly identical, with total CPE and CPE7 values between 4 and 5 fish/mile, CPE11 values were both 1.5 fish/mile, and CPE14 values were both 0.3 fish/mile. There were never enough fish captured to allow for PSD calculations, but the smallmouth bass fishery was stable and helped to provide a nice bass fishery for anglers.

Following the breach, large fingerling smallmouth bass (mean length 4.0 inches) were stocked in the fall of 2009, and yearling smallmouth bass (mean length 4.5 inches) were stocked in the spring of 2010. These would have been age 5 fish during the 2014 survey. These stocked fish likely composed the vast majority of the catch in post-breach electrofishing surveys, although single large smallmouth bass were present in spring surveys in 2011 and 2013; these fish would have been much older than the stocked fish and would have escaped Mirror Lake into Lake Delton. The single age 9 fish in the 2014 survey falls into this category as well. The predominant age class in the 2014 survey was age 4, with significantly fewer age 5 fish. It is possible, however, that our method of aging dorsal spine sections from bass ˃ 8 inches (scales are used for fish ≤ 8 inches) caused us to underestimate the ages of the older fish by one year due to the eroded central lumen often found in dorsal spines of bass. A portion of the age 3, age 4, and age 5 fish may have been one year older (or more). Smallmouth bass escape from Mirror Lake into Lake Delton and supplement the stocked fish as well as fish naturally reproduced in Lake Delton. This was apparent when the fall 2009 electrofishing survey occurred prior to the first stocking of smallmouth bass after the breach, and smallmouth bass ranging from 5.6 to 6.8 inches were captured. Based on length at age data from smallmouth bass collected in Mirror Lake and

Lake Delton in 2014, these 2009 fish were likely age 1+ (hatched in 2008, 2 growing seasons by late September 2009).

Catch rates of smallmouth bass following the breach have begun to come into line with what was observed prior to the breach. Catch rates of larger fish are slowly beginning to increase as the initial stocked fish grow older (Table 14). The CPE of 25.6 fish/mile in the fall 2014 survey represents the highest catch rate of smallmouth bass either before or since the breach, and may indicate that the population is reaching levels higher than ever before.

Yellow perch were more abundant in Lake Delton prior to the breach. The 1995 comprehensive survey saw 435 yellow perch collected, and the catch rate was 24.2 fish/net night which was 60 times greater than the 2014 SN1 catch rate. Ages 2 through 6 were present in the 1995 sample. In 2014, only age 3 and age 4 fish were collected, with age 4 being the most common (56%). Mean lengths at ages 3 and 4 were similar when comparing data from 1995 to 2014 (Figure 50). Because yellow perch were not stocked following the breach, the fish captured in 2014 came to Lake Delton by passing downstream from Mirror Lake or Lake Blass. Age 1 fish typically are not present in the SN1 catch, and this is most likely due to them not being vulnerable to the sampling gear. Age 2 yellow perch are often present in the SN1 catch in other lakes, but their absence here is most likely due to a combination of a couple of factors. A low-level adult population leads to low amounts of natural perch reproduction, and high densities of black and white crappies and stocked walleyes quickly consume any offspring that are produced, ensuring that these fish do not recruit to the adult population. The yellow perch population in Lake Delton provides a very minor component of the fishery from an angler’s perspective, and is likely to persist at low levels, primarily through escapement of fish from Mirror Lake and possibly Lake Blass.

REFERENCES

Aday, D. D., R. J. H. Hoxmeier, and D. H. Wahl. 2003. Direct and indirect effects of gizzard shad on bluegill growth and population size structure. Transactions of the American Fisheries Society 132(1): 47-56.

Anderson, R. O., and R. M. Neumann. 1996. Length, weight, and associated structural indices. Pages 447-482 in B. R. Murphy and D.W. Willis editors. Fisheries techniques, 2nd edition. American Fisheries Society, Bethesda, Maryland.

Ball, J. R., T. Smith, and C. W. Threinen. 1971. Surface water resources of Sauk County. Wisconsin Department of Natural Resources, Madison, Wisconsin. 64 pp.

Becker, G. C. 1983. Fishes of Wisconsin. The University of Wisconsin Press. Madison, Wisconsin.

Bettoli, P.W., and L.E. Miranda. 2001. Cautionary note about estimating mean length at age with subsampled data. North American Journal of Fisheries Management 21: 425-428.

Dettmers, J. M., and R. A. Stein. 1992. Food consumption by larval gizzard shad: zooplankton effects and implications for reservoir communities. Transactions of the American Fisheries Society 121(4): 494-507.

DeVries, D. R., and R. A. Stein. 1992. Complex interactions between fish and zooplankton: quantifying the role of an open-water planktivore. Canadian Journal of Fisheries and Aquatic Sciences 49: 1216-1227.

Fuller, D. 1997. Lake Delton Catfish Survey-1996. Wisconsin Department of Natural Resources, Poynette, Wisconsin. 6pp.

Guy, C.S., R.M. Neumann, D.W. Willis, and R.O. Anderson. 2007. Proportional size distribution (PSD): a further refinement of population size structure index terminology. Fisheries 32(7): 348.

Ives, D. 1971. Lake Inventory-Lake Delton, Sauk County. Wisconsin Department of Natural Resources, Poynette, Wisconsin. 29pp.

Laarman, P.W., and J. R. Ryckman. 1982. Relative size selectivity of trap nets for eight species of fish. North American Journal of Fisheries Management 2: 33-37.

Larson, T. 1995. Lake Delton Fishery Survey-1995. Wisconsin Department of Natural Resources, Poynette, Wisconsin. 27pp.

Lewis, W. M., R. Heidinger, and M. Konikoff. 1968. Loss of fishes over the drop box spillway of a lake. Transactions of the American Fisheries Society 97(4): 492-494.

Murphy, B. R., D. W. Willis, and T. A. Springer. 1991. The relative weight index in fisheries management: status and needs. Fisheries 16(2): 30-38.

Priegel, G. R. 1975. Age and growth of the yellow bass in Lake Poygan, Wisconsin. Transactions of the American Fisheries Society 104(3): 513-515.

Ricker, W. E. 1975. Computation and interpretation of biological statistics of fish populations. Fisheries Research Board of Canada Bulletin 191.

Weber, M. J., M. Flammang, and R. Schultz. 2013. Estimating and evaluating mechanisms related to walleye escapement from Rathbun Lake, Iowa. North American Journal of Fisheries Management 33: 642-651.

Willis, D.W., B. R. Murphy, and C. S. Guy. 1993. Stock density indices: development, use, and limitations. Reviews in Fisheries Science 1:3, 203-222.

TABLES AND FIGURES Table 1. Current fishing regulations for Lake Delton, Sauk County, Wisconsin. Species Season Dates Length and Bag Limits No minimum length limit and the daily bag Catfish Open All Year limit is 10. Panfish (bluegill, pumpkinseed, sunfish, crappie, No minimum length limit and the daily bag Open All Year and yellow perch) limit is 25. First Saturday in May through the first The minimum length limit is 14" and the daily Largemouth bass and smallmouth bass Sunday in March bag limit is 5. First Saturday in May through the first The minimum length limit is 26" and the daily Northern pike Sunday in March bag limit is 2. First Saturday in May through the first The minimum length limit is 15" and the daily Walleye, sauger, and hybrids Sunday in March bag limit is 5. No minimum length limit and the daily bag Bullheads Open All Year limit is unlimited. No minimum length limit and the daily bag Rock, yellow (striped), and white bass Open All Year limit is unlimited. No minimum length limit and the daily bag Rough fish Open All Year limit is unlimited.

Table 2. Stocking history (2009-2014) for Lake Delton, Sauk County, Wisconsin. Year Species Strain (stock) Age Class Number Avg. Length (inches) Source 2009 WHITE SUCKER UNSPECIFIED FRY 160,000 0.5 PRIVATE HATCHERY 2009 WHITE SUCKER UNSPECIFIED ADULT 0 15.0 PRIVATE HATCHERY 2009 GOLDEN SHINER UNSPECIFIED ADULT 25,200 4.0 PRIVATE HATCHERY 2009 FATHEAD MINNOW UNSPECIFIED ADULT 603,825 2.1 PRIVATE HATCHERY 2009 BLUEGILL UNSPECIFIED FALL YEARLING 23,000 3.7 PRIVATE HATCHERY 2009 WALLEYE ROCK-FOX LARGE FINGERLING 4,387 6.3 DNR COOP PONDS 2009 CHANNEL CATFISH UNSPECIFIED LARGE FINGERLING 2,175 7.3 PRIVATE HATCHERY 2009 SMALLMOUTH BASS UNSPECIFIED LARGE FINGERLING 3,500 4.0 PRIVATE HATCHERY 2009 WALLEYE ROCK-FOX SMALL FINGERLING 9,345 1.4 DNR HATCHERY 2010 SMALLMOUTH BASS UNSPECIFIED YEARLING 1,667 4.5 FEDERAL HATCHERY 2010 WALLEYE UNSPECIFIED YEARLING 1,000 7.5 PRIVATE HATCHERY 2010 FATHEAD MINNOW UNSPECIFIED YEARLING 265,000 2.5 PRIVATE HATCHERY 2010 LARGEMOUTH BASS UNSPECIFIED LARGE FINGERLING 6,675 3.3 DNR PONDS 2010 WALLEYE ROCK-FOX LARGE FINGERLING 1,013 5.6 DNR COOP PONDS 2010 BLUEGILL UNSPECIFIED LARGE FINGERLING 2,000 2.0 FEDERAL HATCHERY 2010 WALLEYE UNSPECIFIED LARGE FINGERLING 1,670 8.0 PRIVATE HATCHERY 2010 BLUEGILL UNSPECIFIED LARGE FINGERLING 22,995 3.0 PRIVATE HATCHERY 2010 CHANNEL CATFISH UNSPECIFIED LARGE FINGERLING 1,000 8.0 PRIVATE HATCHERY 2010 WALLEYE ROCK-FOX SMALL FINGERLING 4,806 1.7 DNR HATCHERY 2011 FATHEAD MINNOW UNSPECIFIED ADULT 1,199,980 2.0 PRIVATE HATCHERY 2011 WALLEYE ROCK-FOX LARGE FINGERLING 1,382 7.4 DNR COOP PONDS 2011 BLUEGILL UNSPECIFIED LARGE FINGERLING 26,700 1.5 FEDERAL HATCHERY 2011 WALLEYE ROCK-FOX SMALL FINGERLING 9,345 1.5 DNR HATCHERY 2013 NORTHERN PIKE UNSPECIFIED FRY 70,000 1.0 PRIVATE HATCHERY 2013 FATHEAD MINNOW UNSPECIFIED ADULT 40,000 2.0 PRIVATE HATCHERY 2013 WALLEYE ROCK-FOX LARGE FINGERLING 3,554 5.9 DNR COOP PONDS 2013 BLUEGILL UNSPECIFIED LARGE FINGERLING 40,000 2.0 PRIVATE HATCHERY 2014 WALLEYE ROCK-FOX LARGE FINGERLING 1,258 6.0 DNR COOP PONDS 2014 WALLEYE UNSPECIFIED LARGE FINGERLING 700 7.0 PRIVATE HATCHERY

Table 3. Locations of fyke nets (GPS coordinates) used during the spring fyke netting survey (SN1) of Lake Delton, Sauk County, Wisconsin in 2014. Net Number Date First Set Date Last Lifted Latitude (N) Longitude (W) 1 04/03/2014 04/09/2014 43.59073 -89.78689 2 04/07/2014 04/21/2014 43.59087 -89.78671 3 04/07/2014 04/11/2014 43.59285 -89.78661 4 04/09/2014 04/23/2014 43.59357 -89.78764 5 04/10/2014 04/23/2014 43.59561 -89.78027 6 04/10/2014 04/15/2014 43.60575 -89.78143 7 04/11/2014 04/23/2014 43.59851 -89.77513 8 04/11/2014 04/23/2014 43.59753 -89.78479 9 04/11/2014 04/15/2014 43.60218 -89.77957 10 04/21/2014 04/23/2014 43.60373 -89.77447

Table 4. Hard structures used to estimate age for the various fish species collected during the 2014 survey of Lake Delton, Sauk County, WI. Species Size Category Structure Black Crappie ALL scale Bluegill ALL scale Largemouth Bass ≤8 inches scale Largemouth Bass ≥8 inches dorsal spine Northern Pike ALL first anal fin ray Smallmouth Bass ≤8 inches scale Smallmouth Bass ≥8 inches dorsal spine Walleye ≤8 inches scale Walleye ≥8 inches dorsal spine White Crappie ALL scale Yellow Perch ALL anal fin spine

Table 5. Locations of electrofishing stations (GPS coordinates) sampled during spring and fall electrofishing surveys of Lake Delton, Sauk County, Wisconsin in 2014. Start Latitude Start Longitude End Longitude Date Station Distance (miles) (N) (W) End Latitude (N) (W) 05/20/2015 Panfish 1 0.5 43.59731 -89.77658 43.60024 -89.77205 05/20/2015 Gamefish 1 1.5 43.60024 -89.77205 43.60576 -89.78095 05/20/2015 Panfish 2 0.5 43.60576 -89.78095 43.60628 -89.78294 05/20/2015 Gamefish 2 3.4 43.60628 -89.78294 43.60024 -89.77204 09/29/2014 Panfish 1 0.5 43.59056 -89.78625 43.59630 -89.78150 09/29/2014 Gamefish 1 1.5 43.59630 -89.78150 43.60118 -89.76947 09/29/2014 Panfish 2 0.5 43.60118 -89.76947 43.60408 -89.77471 09/29/2014 Gamefish 2 1.5 43.60408 -89.77471 43.60144 -89.77995

Table 6. Length categories (inches) that have been proposed for the sport fish species collected from Lake Delton in 2014 (Anderson and Neumann 1996). Species Stock Quality Preferred Memorable Trophy Bluegill 3 6 8 10 12 Black crappie 5 8 10 12 15 Largemouth bass 8 12 15 20 25 Northern pike 14 21 28 34 44 Smallmouth bass 7 11 14 17 20 Walleye 10 15 20 25 30 White crappie 5 8 10 12 15 Yellow perch 5 8 10 12 15

Table 7. Summary of catch and catch per unit effort (CPE) by gear type for SN1, SE1, SE2, and fall electrofishing on Lake Delton, Sauk County, Wisconsin in 2014. CATCH CPUE Fall fish/net SE1 SE2 Fall Species1 Fyke SE1 SE2 EF Total night fish/hour fish/hr Fall EF fish/hr SE1 fish/mile SE2 fish/mile fish/mile White sucker 2,092 0 0 11 2,103 24.0 0.0 0.0 16.9 0.0 0.0 10.0 Black crappie 1,492 0 121 48 1,661 17.1 0.0 242.0 73.8 0.0 121.0 43.6 Common carp 204 0 501 39 744 2.3 0.0 1002.0 60.0 0.0 84.9 6.6 Walleye 249 235 104 140 728 2.9 71.2 37.1 23.6 39.6 17.6 280.0 Bluegill 553 0 18 126 697 6.4 0.0 36.0 193.8 0.0 18.0 114.5 Northern pike 382 14 5 1 402 4.4 4.2 10.0 1.5 2.4 0.8 0.9 Yellow bass 38 0 260 47 345 0.4 0.0 520.0 0.5 0.0 260.0 0.5 LMB 28 56 49 105 238 0.3 17.0 49.0 25.6 9.4 8.3 25.6 Y. bullhead 189 0 0 7 196 2.2 0.0 0.0 0.1 0.0 0.0 2.1 SMB 5 15 18 105 143 0.1 4.5 6.4 50.4 2.5 3.1 25.6 White crappie 97 0 7 0 104 1.1 0.0 14.0 0.0 0.0 7.0 0.0 Yellow perch 31 0 1 5 37 0.4 0.0 2.0 7.7 0.0 1.0 4.5 Pumpkinseed 28 0 0 5 33 0.3 0.0 0.0 0.1 0.0 0.0 4.5 Bl. bullhead 30 0 0 0 30 0.3 0.0 0.0 0.0 0.0 0.0 0.0 Golden shiner 13 0 9 3 25 0.1 0.0 18.0 4.6 0.0 9.0 2.7 Br. silverside 0 0 0 2 2 0.0 0.0 0.0 3.1 0.0 0.0 1.8 White bass 1 0 0 0 1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 5,432 320 1,093 644 7,489 1Largemouth bass is abbreviated LMB, yellow bullhead is abbreviated Y. bullhead, smallmouth bass is abbreviated SMB, black bullhead is abbreviated Bl. Bullhead, and brook silverside is abbreviated Br. silverside.

Table 8. Summary of lengths (inches), size distribution, and ages of panfish collected during the 2014 comprehensive survey of Lake Delton, Sauk County, Wisconsin. Number Length Mean Median Minimum Maximum Species Period Measured Range Length Length Mode PSD PSD-H1 PSD-P Age Age Bluegill SN1 553 3.1-7.7 6.0 6.1 6.4 59 5 0 2 7 Bluegill SE2 18 4.6-7.0 5.8 5.8 4.6 Bluegill Fall 126 1.7-7.6 5.6 5.7 6.5 45 7 0 Black crappie SN1 514 6.3-9.4 8.3 8.4 8.5 77 4 0 2 6 Black crappie SE2 121 5.8-9.1 7.2 6.8 6.5 31 1 0 Black crappie SN1+SE2 635 5.8-9.4 8.1 8.3 8.5 68 4 0 2 6 Black crappie Fall 48 2.7-10.2 6.7 8.0 3.2 Yellow perch SN1-M 14 5.3-7.4 6.4 6.7 6.7 3 4 Yellow perch SN1-F 17 6.2-8.5 7.1 7.1 7.1 3 4 Yellow perch SN1-ALL 31 5.3-8.5 6.8 6.8 6.7 White crappie SN1, SE2 104 6.8-10.0 8.7 8.8 8.9 84 37 1 2 5 1PSD-H categories are 7 inches for bluegills and 9 inches for black and white crappies. These are sizes that anglers often find acceptable for harvest, but which have no official PSD category/designation.

Table 9. Summary of catch, CPE, lengths, and size distribution for black crappies collected during surveys of Lake Delton before and after the 2008 breach. CPE CPE Length Mean Year Date Method N (fish/mile)1 (fish/hr) Range Length PSD PSD-9 PSD-P 1995 March Fyke 1,593 88.5 3.3-11.2 6.6 5 4 1 1995 05/17/1995 EF 14 28.0 2.0-10.9 1995 06/01/1995 EF 21 42.0 2.0-10.9 1995 10/11/1995 EF 8 24.2 3.0-7.9 2009 09/23/2009 EF 44 58.7 53.3 3.4-5.0 4.0 2010 05/24/2010 EF 27 20.8 45.0 3.6-5.2 4.2 2010 10/14/2010 EF 40 32.0 50.0 5.2-6.6 5.9 2011 05/23/2011 EF 254 254.0 379.1 5.0-6.7 6.0 0 0 0 2011 10/11/2011 EF 116 116.0 232.0 6.6-8.2 7.3 1 0 0 2012 05/07/2012 EF 138 138.0 230.0 4.7-8.2 7.5 6 0 0 2014 April Fyke 1,492 17.1 6.3-9.4 8.3 77 4 0 2014 05/20/2014 EF 121 121.0 242.0 5.8-9.1 7.2 31 1 0 2014 09/29/2014 EF 48 43.6 73.8 2.7-10.2 6.7 pre-breach spring mean 35.0 pre-breach fall mean 24.2 post-breach spring mean 133.5 224.0 post-breach fall mean 62.6 102.3 1March 1995 and April 2014 crappie CPE is fish/net night instead of fish/mile. These values are not included in average CPE calculations.

Table 10. Results of Chapman-modified Petersen population estimates for walleyes in Lake Delton in 2014. Group M C R LL N UL LL/acre N/acre UL/acre Adults ≥ 15 inches 36 5 1 47 110 216 0.2 0.4 0.9 All sexually mature fish regardless of size 152 23 6 302 524 1,094 1.2 2.1 4.4 Sexually mature fish plus unknowns ≥ 12 inches 226 91 12 997 1,606 2,831 4.0 6.4 11.4

Table 11. Summary of catch, CPE, lengths, and size distribution for gamefish collected during the 2014 comprehensive survey of Lake Delton, Sauk County, Wisconsin. N Min Max Mean Median Min Max Species Period Sex Measured Length Length Length Length Mode PSD PSD-H1 PSD-P PSD-M Age Age NOP SN1 All 242 11.8 41.1 27.7 27.0 25.8 91 60 46 14 3 7 NOP SN1 F 66 18.9 41.1 31.7 33.7 34.5 3 7 NOP SN1 M 175 17.2 34.6 26.3 26.1 29.2 89 54 37 1 3 6 NOP SN1 U 1 11.8 NOP SE1, SE2 U 8 21.7 36.1 27.4 25.9 LMB Spring-All U 128 6.8 18.3 11.6 11.7 11.7 47 16 8 0 2 7 LMB Fall U 105 3.0 17.7 11.3 11.0 10.3 26 8 3 0 SMB Spring-All U 38 6.1 20.5 11.6 11.8 11.8 2 9 SMB Fall U 105 5.5 16.4 9.1 9.2 9.2 WAE Spring-All All 548 4.4 26.5 11.0 12.6 12.9 13 2 0 1 14 WAE Fyke All 233 6.9 26.5 14.0 13.5 13.2 17 3 0 WAE SE1 All 223 4.4 21.6 9.0 6.9 6.4 WAE SE2 U 92 4.5 16.7 8.7 7.1 5.7 WAE SN1+SE1 F 22 13.5 26.5 18.6 18.0 16.1 3 14 WAE SN1+SE1 M 144 11.1 18.8 13.6 13.4 13.2 12 0 0 2 6 WAE Fall U 140 4.4 17.5 9.1 8.5 6.7 1PSD-H corresponds to lengths that anglers normally find acceptable for harvest of panfish, or lengths at which gamefish maybe legally harvested in Wisconsin. The PSD-H values are 26 inches for northern pike and 14 inches for largemouth and smallmouth bass.

Table 12. Summary of catch, CPE, lengths, and size distribution for walleyes collected during electrofishing surveys of Lake Delton before and after the 2008 breach and subsequent renovation and restocking in 2009. Effort Total CPE- Size Mean Year Date (miles) Catch ALL1 CPE10 CPE15 CPE18 CPE20 Range PSD PSD-18 PSD-20 Length 1998 05/21/1998 6.4 76 11.9 5.5 3.3 1.3 0.9 5.0-23.4 1998 10/07/1998 6.4 139 21.7 12.8 4.7 2.2 0.6 6.0-24.4 2000 05/16/2000 5.8 153 26.4 3.8 3.3 1.6 1.0 4.5-22.9 2000 10/09/2000 6.6 109 16.5 15.0 7.0 3.2 1.2 8.0-26.4 2001 10/03/2001 6.2 176 28.4 11.8 6.9 0.8 0.2 4.5-20.4 2002 10/07/2002 5.8 214 36.9 32.8 7.6 2.6 0.9 6.0-24.4 23 8 3 2003 09/23/2003 6.0 187 31.2 13.7 6.5 0.8 0.2 5.5-20.4 2003 10/13/2003 6.0 283 47.2 18.2 11.0 2.3 1.2 5.0-27.9 60 13 6 2005 09/27/2005 1.9 79 41.6 22.6 13.7 1.6 0.0 5.8-19.5 2009 09/23/2009 0.8 24 30.0 11.3 0.0 0.0 0.0 8.6-10.7 9.8 2010 05/24/2010 1.3 24 18.5 14.6 0.0 0.0 0.0 6.2-12.2 10.7 2010 10/14/2010 1.3 41 31.5 14.6 2.3 0.0 0.0 5.1-15.4 9.8 2011 4/20-21/2011 9.6 533 55.3 38.1 2.5 0.2 0.0 4.7-19.3 7 1 0 11.2 2011 05/23/2011 4.0 176 44.0 21.0 2.8 1.3 0.5 5.1-21.4 10.2 2012 05/07/2012 4.0 154 38.5 4.3 0.3 0.0 0.0 4.6-17.5 7.4 2013 04/30/2013 3.1 113 36.5 36.5 0.3 0.0 0.0 10.2-18.2 1 1 0 12.4 2014 04/30/2014 5.9 235 39.8 15.6 0.8 0.3 0.2 4.4-21.6 9.0 2014 05/20/2014 5.9 104 17.6 7.3 0.3 0.0 0.0 4.5-16.7 9.2 2014 09/29/2014 4.1 140 34.1 13.9 1.2 0.0 0.0 4.4-17.5 9.1 Pre-breach 29.1 15.1 6.3 1.8 0.7 Post-breach 34.6 17.5 1.5 0.2 0.1 1Catch per unit effort (CPE) values expressed as fish/mile.

Table 13. Summary of catch, CPE, lengths, and size distribution for bluegills collected during surveys of Lake Delton before and after the 2008 breach and subsequent renovation and restocking in 2009. Total CPE Length Mean Year Date Gear Catch (fish/mile)1 CPE (fish/hr) Range Length2 PSD PSD-7 PSD-P 1995 05/17/1995 Boomshocker 20 40.0 3.0-6.9 1995 06/01/1995 Boomshocker 102 204.0 2.0-8.9 1995 10/11/1995 Boomshocker 84 254.5 1.0-6.9 2009 09/23/2009 Boomshocker 1 1.3 2.2 8.1 2010 05/24/2010 Boomshocker 9 6.9 15.0 4.0-6.3 5.2 2010 10/14/2010 Boomshocker 5 4.0 6.3 5.1-7.1 6.4 2011 05/23/2011 Boomshocker 22 22.0 32.8 2.3-6.4 5.0 2011 10/11/2011 Boomshocker 44 44.0 88.0 3.4-6.4 4.7 2012 05/07/2012 Boomshocker 37 37.0 61.7 1.3-7.4 4.2 2014 April Fyke 553 3.1-7.7 6.0 59 5 0 2014 05/20/2014 Boomshocker 18 18.0 36.0 4.6-7.0 5.8 2014 09/29/2014 Boomshocker 126 114.5 252.0 1.7-7.6 5.6 45 7 0 Pre-breach spring mean 122.0 Pre-breach fall mean 254.5 Post-breach spring mean 21.0 36.4 Post-breach fall mean 41.0 87.1 1Distance shocked not available for 1995 survey. 2Mean lengths are not available for 1995 surveys because fish were tallied by length groups and individual fish measurements were not recorded.

Table 14. Summary of catch, CPE, lengths, and size distribution for largemouth bass collected during surveys of Lake Delton before and after the 2008 breach and subsequent renovation and restocking in 2009. Total Effort CPE- Length Mean Date Catch (miles) ALL1 CPE8 CPE12 CPE14 CPE15 PSD PSD-14 PSD-P Range Length2 05/21/1998 207 6.4 32.3 30.5 19.7 5.5 3.3 65 18 11 3.0-18.9 10/07/1998 123 6.4 19.2 14.7 8.0 4.8 3.0 3.0-19.4 05/16/2000 135 5.8 23.3 21.4 11.4 8.6 6.9 53 40 32 3.0-20.4 10/09/2000 164 6.6 24.8 23.0 7.6 4.4 3.6 33 19 16 5.5-19.4 10/03/2001 212 6.2 34.2 26.3 13.9 4.4 3.1 53 17 12 3.0-19.9 10/07/2002 337 5.8 58.1 47.6 15.5 7.1 3.1 33 15 7 3.0-20.9 09/23/2003 247 6.0 41.2 35.3 8.3 4.5 2.5 24 13 7 3.5-19.9 10/13/2003 187 6.0 31.2 28.8 10.5 6.7 3.2 36 23 11 4.5-21.4 09/27/2005 181 1.9 95.3 74.2 45.8 14.7 3.2 62 20 4 3.0-18.4 09/23/2009 74 0.8 98.7 0.0 0.0 0.0 0.0 3.8-7.9 5.7 05/24/2010 51 1.3 39.2 6.9 0.0 0.0 0.0 4.9-9.0 6.6 10/14/2010 40 1.3 32.0 28.0 4.8 1.6 1.6 4.9-19.2 10.2 05/23/2011 180 4.0 45.0 43.5 14.8 1.5 1.5 34 6 6 5.2-19.3 11.2 10/11/2011 64 4.0 16.0 14.0 5.5 2.3 0.8 4.6-17.8 10.8 05/07/2012 80 4.0 20.0 19.5 11.8 3.8 2.3 7.2-20.6 12.4 04/30/2013 35 3.1 11.2 9.6 7.3 3.5 1.3 7.2-20.5 12.3 04/30/2014 56 5.9 9.6 8.9 5.1 1.2 0.3 7.5-15.4 11.8 05/20/2014 49 5.9 8.3 7.5 2.9 1.2 0.2 6.8-16.2 11.4 09/29/2014 105 4.1 25.6 25.4 6.6 2.0 0.7 26 8 3 3.0-17.7 11.3 Pre-breach spring mean 27.8 25.9 15.5 7.0 5.1 Pre-breach fall mean 43.4 35.7 15.7 6.7 3.1 Post-breach spring mean 22.2 16.0 7.0 1.9 0.9 Post-breach fall mean 43.1 16.9 4.2 1.5 0.8 1Catch per unit effort (CPE) values expressed as fish/mile. 2Mean lengths are not available for pre-breach surveys because fish were tallied by length groups and individual fish measurements were not recorded.

Table 15. Mean age at 14.0-14.9 inches TL (MAL14) for largemouth bass populations in 10 Columbia and Sauk County lakes (11 surveys), 2006- 2014. Waterbody County Year MAL14 LMB Density Prey Base Lake Wisconsin Columbia 2012 4.8 Low GZS, BLG Lake Delton Sauk 2014 4.9 Moderate BLG Park Lake Columbia 2011 5.3 Low GZS, BLG Swan Lake Columbia 2009 5.8 Moderate GZS, BLG Redstone Lake Sauk 2010 6.0 Low GZS, BLG Seeley Lake Sauk 2008 6.1 Moderate BLG Mirror Lake Sauk 2014 6.4 Moderate BLG White Mound Lake Sauk 2013 6.5 High BLG Dutch Hollow Lake Sauk 2006 6.9 High BLG White Mound Lake Sauk 2006 7.2 High BLG Devils Lake Sauk 2013 9.3 High BLG Mean-All Lakes 6.3 Median-All Lakes 6.1

Table 16. Summary of catch, CPE, lengths, and size distribution for smallmouth bass collected during surveys of Lake Delton before and after the 2008 breach and subsequent renovation and restocking in 2009. Year Month Total Catch Effort (miles) CPE1-ALL CPE7 CPE11 CPE14 Length Range Mean Length2 1998 05/21/1998 28 6.4 4.4 3.8 1.3 0.2 4.0-14.4 1998 10/07/1998 7 6.4 1.1 0.8 0.3 0.0 4.5-11.9 2000 05/16/2000 28 5.8 4.8 4.7 1.7 0.5 6.5-16.9 2000 10/09/2000 7 6.6 1.1 0.9 0.8 0.0 6.5-12.4 2001 10/03/2001 12 6.2 1.9 1.9 1.6 0.6 7.5-17.4 2002 10/07/2002 12 5.8 2.1 1.9 0.0 0.0 4.5-10.4 2003 09/23/2003 33 6.0 5.5 5.0 0.7 0.0 6.0-12.9 2003 10/13/2003 25 6.0 4.2 3.8 1.2 0.3 4.0-17.4 2005 09/27/2005 18 1.9 9.5 9.5 4.7 1.1 8.9-14.8 11.4 2009 09/23/2009 6 0.8 7.5 0.0 0.0 0.0 5.6-6.8 6.0 2010 05/24/2010 6 1.3 4.6 3.1 0.0 0.0 6.2-7.8 7.1 2010 10/14/2010 4 1.3 3.1 2.3 0.0 0.0 6.5-8.3 7.5 2011 05/23/2011 26 4.0 6.5 3.5 0.3 0.3 5.3-17.1 7.5 2011 10/11/2011 24 4.0 6.0 5.5 0.0 0.0 6.6-10.2 8.1 2012 05/07/2012 17 4.0 4.3 4.3 0.0 0.0 7.1-8.8 8.2 2013 04/30/2013 17 3.1 5.4 5.1 2.6 0.3 6.6-18.5 11.0 2014 04/30/2014 15 5.9 2.5 2.5 1.9 0.5 7.0-15.3 12.0 2014 05/20/2014 18 5.9 5.0 2.9 1.9 0.2 6.1-20.5 11.1 2014 09/29/2014 105 4.1 25.6 22.4 2.4 0.5 5.5-16.4 9.1 Pre-breach spring mean 4.6 4.2 1.5 0.3 Pre-breach fall mean 4.2 4.0 1.5 0.3 Post breach spring mean 4.7 3.6 1.1 0.2 Post-breach fall mean 10.6 7.6 0.6 0.1 Post-breach minus 2014 5.5 2.6 0.0 0.0 1Catch per unit effort (CPE) values are expressed as fish per mile. 2Mean lengths are not available for most pre-breach surveys because fish were tallied by length groups and individual fish measurements were not recorded.

250

200

150

100 Fyke SE2

50 Frequency (count) Frequency

3.5 2.5 3.0 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 Length (inches) Figure 1. Length frequency distribution of black crappies collected during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

5 Frequency (count) Frequency

2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 Length (inches) Figure 2. Length frequency distribution of black crappies collected during the fall 2014 electrofishing survey of Lake Delton, Sauk County, Wisconsin.

300

250

200

150

100

Frequency (count) Frequency 50

0 2 3 4 5 6 Age Figure 3. Age frequency distribution of black crappies collected during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

12 11

10 9

8 8.6 8.4 7 7.6 Lake Delton

Length (inches) Length 6 7.2 Region Average 5 6.4 State Average 4 1 2 3 4 5 6 Age Figure 4. Mean length at age of black crappies collected during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin. Error bars represent minimum and maximum length values for a given age.

12 11.3 11 10.1 9.8 10

9 8.4 8 8.4 8.6 6.4 7 7.6 6 7.2 5 3.8 6.0 4

Length (inches) Length 3 1995 2 1 2014 0 1 2 3 4 5 6 Age Figure 5. Mean length at age of black crappies captured during surveys of Lake Delton, Sauk County, Wisconsin in 1995 and 2014. Values from the 1995 survey are represented in the white boxes with the gray border. Values from 2014 are represented in the gray boxes with no border.

150 y = -2.87x + 120.94

125 R² = 0.27

100

50 Lake Delton

Relative weight Relative WR = 100 25 Wr = 75 Linear (Lake Delton) 0 5.0 6.0 7.0 8.0 9.0 10.0 Length (inches) Figure 6. Relative weights of black crappies captured during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

80 70 60 50 40 30

20 Frequency (count) Frequency 10

4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5

12.0 20.5 10.0 10.5 11.0 11.5 12.5 13.0 13.5 14.0 14.5 15.0 15.5 16.0 16.5 17.0 17.5 18.0 18.5 19.0 19.5 20.0 21.0 21.5 22.0 22.5 23.0 23.5 24.0 24.5 25.0 25.5 26.0 26.5 Length (inches) Figure 7. Length frequency distribution of walleyes collected during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

250

200

150

100

50 Frequency (count) Frequency

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Age Figure 8. Age frequency distribution of walleyes collected during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

30 26.5 25 21.3 22.9

18.0

20 14.3 13.2 15 11.5 6.3 10 Lake Delton Region Average Length (inches) Length 5 State Average 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Age Figure 9. Mean length at age of walleyes collected during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin. Error bars represent minimum and maximum length values for a given age.

90 80

70 60 50 40 30 Females 20 Males Frequency (count) Frequency 10 0 2 3 4 5 6 7 8 9 10 11 12 13 14 Age Figure 10. Age frequency distribution of walleyes (separated by sex) collected during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

18.2 15 17.0

14.1 13.0 10 11.9

Length (inches) Length 5

Lake Delton Males 0 1 2 3 Age 4 5 6 Figure 11. Mean length at age of male walleyes collected during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin. Error bars represent minimum and maximum length values for a given age.

25 19.7

20 17.7 15.3 18.2 15 17.0 14.1 13.0

10 11.9 Length (inches) Length 5 1995 2014 0 1 2 3 4 5 6 Age Figure 12. Mean length at age of male walleyes captured during surveys of Lake Delton, Sauk County, Wisconsin in 1995 and 2014. Values from the 1995 survey are represented in the white boxes with the gray border. Values from 2014 are represented in the gray boxes with no border.

25 26.5

22.9 20 22.4

18.9 15 17.1 14.8 10

Length (inches) Length 5 Lake Delton Females 0 1 2 3 4 5 6 7 8 9 10 11 12 Age Figure 13. Mean length at age of female walleyes collected during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin. Error bars represent minimum and maximum length values for a given age.

30 26.7 24.9 25 26.5

18.9 20 17.7 22.9 16.1 22.4 18.9 15 17.1 14.8 10 1995 Length (inches) Length 5 2014 0 3 4 5 6 7 8 9 10 11 12 13 14 Age Figure 14. Mean length at age of female walleyes captured during surveys of Lake Delton, Sauk County, Wisconsin in 1995 and 2014. Values from the 1995 survey are represented in the white boxes with the gray border. Values from 2014 are represented in the gray boxes with no border. 30

Frequency (count) Frequency 5

4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5

10.5 15.0 10.0 11.0 11.5 12.0 12.5 13.0 13.5 14.0 14.5 15.5 16.0 16.5 17.0 17.5 Length (inches) Figure 15. Length frequency distribution of walleyes collected during the fall 2014 electrofishing survey of Lake Delton, Sauk County, Wisconsin.

150

125

100

75 Females

50 Males Relative weight Relative 25 Wr = 100 Wr = 75

15.0 16.0 17.0 18.0 19.0 20.0 21.0 22.0 23.0 24.0 25.0 Length (inches)

Figure 16. Relative weights of walleyes collected during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

200 180

160 140 120 100 80 Fyke 60 SE2 40 Frequency (count) Frequency 20

4.0 7.0 1.5 2.0 2.5 3.0 3.5 4.5 5.0 5.5 6.0 6.5 7.5 Length (inches) Figure 17. Length frequency distribution of bluegills collected during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

Frequency (count) Frequency 5

5.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.5 6.0 6.5 7.0 7.5 Length (inches) Figure 18. Length frequency distribution of bluegills collected during the fall 2014 electrofishing survey of Lake Delton, Sauk County, Wisconsin.

300

250

200

150

100

Frequency (count) Frequency 50

0 2 3 4 5 6 7 Age Figure 19. Age frequency distribution of bluegills collected using fyke nets during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

6 6.8 7.4 6.5

4 6.1 Lake Delton

Length (inches) Length 5.0 Region Average 2 4.8 State Average 0 1 2 3 4 5 6 7 8 9 10 Age Figure 20. Mean length at age of bluegills collected using fyke nets during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin. Error bars represent minimum and maximum length values for a given age.

9 8.3 8.5 7.7 8 6.9

7 6.2 7.4 6 6.8 4.8 5.0 6.5 5 6.1 4 4.5 3 3.4 Length (inches) Length 2 1995 1 2014 0 1 2 3 4 5 6 7 8 Age Figure 21. Mean length at age of bluegills captured during surveys of Lake Delton, Sauk County, Wisconsin in 1995 and 2014. Values from the 1995 survey are represented in the white boxes with the gray border. Values from 2014 are represented in the gray boxes with no border.

150

125

100

50 Lake Delton BLG

Relative weight Relative Wr = 75 25 Wr = 100 0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 Length (inches) Figure 22. Relative weights of bluegills collected during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

12 10 8 Male NOP 6 Female NOP

4 Frequency (count) Frequency 2

22.5 31.5 40.5 17.0 17.5 18.0 18.5 19.0 19.5 20.0 20.5 21.0 21.5 22.0 23.0 23.5 24.0 24.5 25.0 25.5 26.0 26.5 27.0 27.5 28.0 28.5 29.0 29.5 30.0 30.5 31.0 32.0 32.5 33.0 33.5 34.0 34.5 35.0 35.5 36.0 36.5 37.0 37.5 38.0 38.5 39.0 39.5 40.0 41.0 Length (inches) Figure 23. Length frequency distribution of sexually mature northern pike collected using fyke nets during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

180 160

140 120 100 80 60

Frequency (count) Frequency 40 20 0 3 4 5 6 7 Age Figure 24. Age frequency distribution of northern pike collected using fyke nets during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin. 55

45 40 29.9 23.8 27.2

35 26.7 30 21.0 25 20

15 Lake Delton NOP-ALL Length (inches) Length 10 Region Average 5 State Average 0 1 2 3 4 5 6 7 Age Figure 25. Mean length at age of northern pike collected using fyke nets during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin. Error bars represent minimum and maximum length values for a given age.

180 160

140 120 100 80 Females 60 Males

Frequency (count) Frequency 40 20 0 3 4 5 6 7 Age Figure 26. Age frequency distribution of northern pike (separated by sex) collected using fyke nets during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

50 33.8 40 25.5 26.6 30 25.2

Length (inches) Length 10 Lake Delton Females 0 3 4 5 6 7 Age Figure 27. Mean length at age of female northern pike collected using fyke nets during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin. Error bars represent minimum and maximum length values for a given age.

40 33.8 35 36.6 37.5 37.0 30 26.6 25.2 25.5 30.5 25 29.8 20 23.4 20.6 15

Length (inches) Length 10 1995 5 2014 0 1 2 3 4 5 6 7 8 9 10 Age Figure 28. Mean length at age of female northern pike captured during surveys of Lake Delton, Sauk County, Wisconsin in 1995 and 2014. Values from the 1995 survey are represented in the white boxes with the gray border. Values from 2014 are represented in the gray boxes with no border.

40 35 28.0

27.2 30 23.0 25 19.9 20 15

Length (inches) Length 10 5 Lake Delton Males 0 3 4 5 6 Age Figure 29. Mean length at age of male northern pike collected using fyke nets during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin. Error bars represent minimum and maximum length values for a given age.

30 28.0 27.2 24.7 25 21.3 26.0 19.2 20 23.0 19.9 15

Length (inches) Length 1995 5 2014 0 1 2 3 4 5 6 Age Figure 30. Mean length at age of male northern pike captured during surveys of Lake Delton, Sauk County, Wisconsin in 1995 and 2014. Values from the 1995 survey are represented in the white boxes with the gray border. Values from 2014 are represented in the gray boxes with no border.

150 Male NOP y = 1.00x + 64.53

125 R² = 0.26

100

75 Lake Delton Female NOP 50 Female NOP Lake Delton Male NOP

Relative weight Relative y = 0.93x + 75.04 Wr = 100 25 R² = 0.20 Wr = 75 Linear (Lake Delton Female NOP) Linear (Lake Delton Male NOP) 0 0 5 10 15 20 25 30 35 40 45 Length (inches) Figure 31. Relative weights of northern pike collected using fyke nets during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

6 5 SN1 4 SE1 3 SE2

2 Frequency (count) Frequency 1

6.5 7.0 7.5 8.0 8.5 9.0 9.5

10.0 10.5 11.0 11.5 12.0 12.5 13.0 13.5 14.0 14.5 15.0 15.5 16.0 16.5 17.0 17.5 18.0 Length (inches) Figure 32. Length frequency distribution of largemouth bass collected during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

20 18 16 14 12 10 8 6

Frequency (count) Frequency 4 2

3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5

10.0 10.5 11.0 11.5 12.0 12.5 13.0 13.5 14.0 14.5 15.0 15.5 16.0 16.5 17.0 17.5 Length (inches) Figure 33. Length frequency distribution of largemouth bass collected during the fall 2014 electrofishing survey of Lake Delton, Sauk County, Wisconsin.

Frequency (count) Frequency 10

0 2 3 4 5 6 7 Age

Figure 34. Age frequency distribution of largemouth bass collected during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

20 18.3 15.4 14.4 13.6 15 11.5

9.3 10

Lake Delton 5

Length (inches) Length Region Average State Average 0 2 3 4 5 6 7 Age Figure 35. Mean length at age of largemouth bass captured during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

20 18.2 18 15.4 14.4 18.3 16 13.6 14 16.4 16.4 11.5 14.8 12 13.5 9.3 10 11.8 8 8.8 6

Length (inches) Length 6.5 4 1995 2 2014 0 1 2 3 4 5 6 7 8 9 Age Figure 36. Mean length at age of largemouth bass captured during surveys of Lake Delton, Sauk County, Wisconsin in 1995 and 2014. Values from the 1995 survey are represented in the white boxes with the gray border. Values from 2014 are represented in the gray boxes with no border.

150 y = 1.86x + 82.99

125 R² = 0.18

100

50 Lake Delton

Relative weight Relative Wr = 100 25 Wr = 75 Linear (Lake Delton)

6.0 0.0 1.0 2.0 3.0 4.0 5.0 7.0 8.0 9.0

16.0 10.0 11.0 12.0 13.0 14.0 15.0 17.0 18.0 Length (inches) Figure 37. Relative weights of largemouth bass collected during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

10 Spring Fall

Frequency (count) Frequency 5

8.5 5.5 6.0 6.5 7.0 7.5 8.0 9.0 9.5

15.0 10.0 10.5 11.0 11.5 12.0 12.5 13.0 13.5 14.0 14.5 15.5 16.0 16.5 17.0 17.5 18.0 18.5 19.0 19.5 20.0 20.5 Length (inches) Figure 38. Length frequency distribution of smallmouth bass collected during the spring and fall 2014 surveys of Lake Delton, Sauk County, Wisconsin.

10 8 6

4 Frequency (count) Frequency 2 0 2 3 4 5 6 7 8 9 Age

Figure 39. Age frequency distribution of smallmouth bass collected during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

25 20.5

14.5 12.8 15 11.1 8.6 10 Lake Delton

Length (inches) Length Region Average 5 State Average 0 1 2 3 4 5 6 7 8 9 Age Figure 40. Mean length at age of smallmouth bass collected during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

150

125

100

50 Lake Delton

Relative weight Relative WR = 100 25 Wr = 75

3.0 0.0 1.0 2.0 4.0 5.0 6.0 7.0 8.0 9.0

11.0 10.0 12.0 13.0 14.0 15.0 16.0 Length (inches) Figure 41. Relative weights of smallmouth bass collected during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

15 Fyke Net 10 SEII

5 Frequency (count) Frequency 0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 Length bin (inches) Figure 42. Length frequency distribution of white crappies collected during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

40 35 30 25 20 15

10 Frequency (count) Frequency 5 0 2 3 4 5 Age Figure 43. Age frequency distribution of white crappies collected during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

12 8.5 10 8.0 9.2

8.5 8

Length (inches) Length Lake Delton 2 State Average 0 1 2 3 4 5 Age Figure 44. Mean length at age of white crappies collected during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

14 11.8 12 10.7

10 8.5 8.0 8 9.2 8.5 7.8 6 7.0

Length (inches) Length 4 4.6 1995 2 2014 0 1 2 3 4 5 Age Figure 45. Mean length at age of white crappies captured during surveys of Lake Delton, Sauk County, Wisconsin in 1995 and 2014. Values from the 1995 survey are represented in the white boxes with the gray border. Values from 2014 are represented in the gray boxes with no border.

150

125 y = -5.33x + 143.51

R² = 0.23 100

75 Lake Delton

50 Wr = 100 Relative weight Relative Wr = 75 25 Linear (Lake Delton) 0 6.0 7.0 8.0 9.0 10.0 Length (inches) Figure 46. Relative weights of white crappies collected during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

6 Unknown 4 Male

Female Frequency (count) Frequency 2

0 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 Length (inches) Figure 47. Length frequency distribution of yellow perch collected during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

20 18

16 14 12 10 8 6

Frequency (count) Frequency 4 2 0 3 4 Age

Figure 48. Age frequency distribution of yellow perch collected during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

10 9

8 7 6 7.1 5 6.3 4

3 Lake Delton Length (inches) Length 2 Region Average 1 State Average 0 1 2 3 4 5 Age Figure 49. Mean length at age of yellow perch collected during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

10 9.3 9 8.5 7.7

8 7 6.3 6 7.1 5 6.0 4 4.9

3 Length (inches) Length 2 1995 1 2014 0 1 2 3 4 5 Age Figure 50. Mean length at age of yellow perch captured during surveys of Lake Delton, Sauk County, Wisconsin in 1995 and 2014. Values from the 1995 survey are represented in the white boxes with the gray border. Values from 2014 are represented in the gray boxes with no border.

150

125

100

75 Females

50 Males Relative weight Relative 25 Wr = 100 Wr = 75 0 5.0 6.0 7.0 8.0 9.0 Length (inches) Figure 51. Relative weights of yellow perch collected during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

Frequency (count) Frequency 10

12.5 13.0 13.5 14.0 14.5 15.0 15.5 16.0 16.5 17.0 17.5 Length (inches) Figure 52. Length frequency distribution of white suckers collected using fyke nets during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

Frequency (count) Frequency 2

19.0 21.0 14.0 14.5 15.0 15.5 16.0 16.5 17.0 17.5 18.0 18.5 19.5 20.0 20.5 21.5 Length (inches) Figure 53. Length frequency distribution of common carp collected using fyke nets during the spring 2014 survey of Lake Delton, Sauk County, Wisconsin.

140

120

100

80 SN1 60 SE2

40 Fall EF Frequency (count) Frequency 20

5.0 3.0 3.5 4.0 4.5 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 Length (inches) Figure 54. Length frequency distribution of yellow bass collected during the spring and fall 2014 surveys of Lake Delton, Sauk County, Wisconsin.