Methods

BOOM SHOCKING1987:A standard WDNR electrofishing boat was used on Lake Mendota set at 300 volts and 2.5 amps (mean) DC, with a 20 % duty cycle and 60 pulses per second. On all sampling dates two people netted fish, the total electrofishing crew was three people. Shocking was divided into stations. For each station, the actual starting and ending time was recorded. Starting and ending points of each station were plotted on a nap. A 7.5 minute topographic map (published 1983) and a cartometer was used to develop a standardized shoreline mileage numbering scheme. Starting at the Yahara River outlet at Tenney Park and measuring counterclockwise, the shoreline was numbered according to the number of miles from the outlet. The length of shoreline shocked for each station was determined using the same maps. The objectives of the fall 1987 electrofishing was: to gather CPE data for comparison with previous surveys of the lake; develop a database for relating fall electroshocker CPE to predator density; collect fall predator diet data; make mark-recapture population estimates of YOY predators; and determine year-class-strength of some nonpredators (yellow perch, yellow bass, and white bass).1993: Electrofishing was used to continue marking largemouth and smallmouth bass (because of low CPE in fyke nets), to recapture fish marked in fyke netting, and to mark and recapture walleyes ( less than 11.0 in.) on Lake Mendota. Four person crews electrofished after sunset from May 05 to June 03, 1993. A standard WDNR electrofishing boat was used, set at about 300 volts and 15.0 amps (mean) DC, with a 20 % duty cycle at 60 pulses per second. On all sampling dates two people netted fish; thus, CPE data are given as catch per two netter hour or mile. Shocking was divided into stations. For each station the actual starting and ending time and the generator s meter times was recorded. Starting and ending points of each station were plotted on a map. 7.5 minute topographic maps (published in 1983) were used in addition to a cartometer to develop a standardized shoreline mileage numbering scheme. Starting at the Yahara River outlet at Tenney Park and measuring counterclockwise the shoreline was numbered according to the number of miles from the outlet. The length of shoreline shocked for each station was determined using these maps. The 4 person electroshocker crews were used again from September 20 to October 19. Fall shocking had several objectives: to gather CPE data for comparison with previous surveys of the lake; develop a database for relating fall electroshocker CPE to piscivore density; and make mark recapture population estimates of young of year (YOY) piscivores.1997:5/13/1997-5/20/1997: Electrofishing was completed at night on lakes: Mendota, Monona, and Waubesa. A standard WDNR electrofishing boat was used, set from 320-420 volts and 16-22 amps DC, with a 20 % duty cycle at 50 pulses per second. Two netters were used for each shocking event. At a particular station, starting and ending times where shocking took place were recorded. The location of the designated shocking stations is unknown.9/23/1997-10/14/1997: Electrofishing was completed at night on Mendota, Monona, Waubesa, and Wingra. A standard WDNR electrofishing boat was used, set from 315-400 volts and 16-24 amps DC, with a 20% duty cycle at 60 pulses per second. Two netters were used for each shocking event. Starting and ending time at each shocking station was listed. The location of the designated shocking stations is unknown.1998:Electrofishing was completed at night on Mendota, Monona, Wingra, and Waubesa from 5/12/1998- 10/28/1998. A standard WDNR electrofishing boat was used, set from 240-410 volts and 15-22 amps DC, with a 20% duty cycle at 50-100 pulses per second. Two netters were used for each shocking event. Starting and ending time at each shocking station was listed. The location of the designated shocking stations is unknown. FYKE NETTING1987:Fyke nets were fished daily from March 17 to April 24, 1987 on Lake Mendota. The nets were constructed of 1.25 inch (stretch) mesh with a lead length of 50 ft. (a few 25 ft. leads were used). The hoop diameter was 3 ft. and the frame measured 3 ft. by 6 ft. Total length of the net was 28 ft. plus the lead length. Nets were set in 48 unknown locations. Initially, effort was concentrated around traditional northern pike spawning sites (Cherokee Marsh, Sixmile Creek, Pheasant Branch Creek, and University Bay). As northern pike catch-per-effort (CPE) declined some nets were moved onto rocky shorelines of the lake to capture walleyes. All adult predators (northern pike, hybrid muskie, largemouth and smallmouth bass, walleye, gar, bowfin, and channel catfish) captured were tagged and scale sampled. Measurements on non-predator species captured in fyke nets were made one day per week. This sampling was used to index size structure and abundance, and to collect age and growth data. In each net, total length and weight of 20 fish of each species caught was measured, and the remaining caught were counted.1993:Same methods as 1987, except fyke nets were fished from 4/8/1993-4/29/1993 on Lake Mendota. The 1993 fyke net data also specifies the &ldquo;mile&rdquo; at which the fyke net was set. This is defined as the number of miles from the outlet of the Yahara River at Tenney Park, moving counterclockwise around the lake. In addition, abundance and lengths of non-gamefish species captured in fyke nets were recorded one day per week. Six nets were randomly selected to sample for non-gamefish data. This sampling was used to index size structure and abundance, and to collect age and growth data. In each randomly selected net, total length and weight was measured for 20 fish of each species, and the remaining caught were counted.1998:There is no formal documentation for the exact methods used for fyke netting from 3/3/1998-8/12/1998 on Lake Mendota. However, given that the data is similar to data collected in 1987 and 1993 it is speculated that the same methods were used.MINI-FYKE NETTING1989:There is no formal documentation for the exact methods used for mini-fyke netting on Lake Mendota and Lake Monona from 7/26/1989-8/25/1989. However, given that the data is similar to data collected from 1990-1993 it is speculated that the same methods were used. In the sampling year of 1989, mini-fyke nets were placed at 22 different unknown stations.1990-1993: Mini-fyke nets were fished on Lake Mendota and Lake Monona during July-September at 20, 29, 13, and 15 sites per month during 1990, 1991, 1992, and 1993, respectively to estimate year-class strength, relative abundance, and size structure of fishes in the littoral zone. Nets were constructed with 3/16 in. mesh, 2 ft. diameter hoops, 2 ft. x 3 ft. frame, and a 25 ft. lead. Sites were comparable to seine sites used in previous surveys. Sites included a variety of substrate types and macrophyte densities. To exclude turtles and large piscivores from minifyke nets, some nets were constructed with approximately 2 in. by 2 in. mesh at the entrance to the net. Thus, mini-fyke net data are most accurate for YOY fishes, and should not be used to make inferences about fishes larger than the exclusion mesh size. 1997:There is no formal documentation for the mini-fyke methods which were used on Lake Waubesa and Lake Wingra from 9/16/1997-9/18/1997. However, given that the data is similar to data collected in 1989, and 1990-1993, it is speculated that the methods used during 1997 are the same. SEINE NETTING1989, 1993: Monthly shoreline seining surveys were conducted on Lake Mendota and Lake Monona during June through September to estimate year class-strength, relative abundance, and size structure of the littoral zone fish community. Twenty sites were identified based on previous studies. Sites included a variety of substrate types and macrophyte densities. Seine hauls were made with a 25ft bag seine with 1/8 inch mesh pulled perpendicular to shore starting from a depth of 1 m. Twenty fish of each species were measured from each haul and any additional fish were counted. Gill Netting (1993)Experimental gill nets were fished in weekly periods during June through August, 1993. Gill nets were used to capture piscivores for population estimates of fish marked in fyke nets. All nets were constructed of five 2.5-4.5 in. mesh panels, and were 125 ft. long. Nets set in water shallower than 10 ft. were 3ft. high or less; all others were 6ft. high or less. Sampling locations were selected randomly from up to three strata: 1) offshore reef sets, 2) inshore sets, 6.0-9.9 ft. deep, and 3) mid-depth sets, 10-29.9 ft. deep. The exact location at which the gill nets were set on the lake is unknown because the latitude and longitude values which were recorded by the WDNR are invalid. Temperature and dissolved oxygen profiles were used to monitor the development of the thermocline and guide net placement during July and August. After the thermocline was established nets were set out to the 30 ft. contour or to the maximum depth with dissolved oxygen greater than 2 ppm. Walleye Age: Scale and Spine Analysis (1987) Scales were taken from walleye that were shocked during the fall of 1987 electrofishing events on Lake Mendota. Scales were taken from 10 fish per one-inch length increment. The scales were removed from behind the left pectoral fin, and from the nape on the left side on esocids. In addition, the second dorsal spine was removed from 10 walleyes per sex and inch increment (to age and compare with scale ages for fish over 20 inches). CREEL SURVEYS1989:Fishing pressure, catch rates, harvest, and exploitation rates were estimated from a randomized, access-point creel survey. The schedule was stratified into weekday and weekend/holiday day types. Shifts were selected randomly and were either 07:00-15:00 h or 15:00-23:00 h. In addition, two 23:00-03:00 h shifts and two 03:00-07:00 h shifts were sampled per month to estimate the same parameters during night time hours. During the ice fishing season (January-February) 22 access points around Lake Mendota and upstream to the Highway 113 bridge were sampled. The clerk counted the number of anglers starting and completing trips during the scheduled stop at each access point. During openwater (March-December) 13 access points were sampled; 10 were boat ramps and 3 were popular shore fishing sites<strong>. </strong>At each of these sites, an instantaneous count of shore anglers was made upon arrival at the site, continuous counts of anglers starting and completing trips at public and private access points were made. Boat occupants and ice fishing anglers were only interviewed if they were completing a trip. Both complete and incomplete interviews were made of shore anglers. Number caught and number kept of each species, and percent of time seeking a particular species were recorded. All predators possessed by anglers were measured, weighed, and inspected for finclips and tags. We measured a random sample of at least 20 fish of each non-predator species per day.1990-1993: Same as 1989, except 23 access points were used during the ice fishing season. In addition, 13 access points were sampled during the openwater (May-December) season; 9 sites were boat ramps and 4 sites were popular shore fishing sites. 1994-1999: No formal documentation exists, but given the similarity in the data and consistency through the years; it is speculated tha tthe methods are the same.

Methods

Sonar Sampling Protocol and Data Generation From 1981-1994, pelagic fish abundance data were collected along a set of transects in each of six lakes (Allequash, Big Muskellunge, Crystal, Sparkling, Trout, Mendota) using a Simrad 70 khz EY-M echosounder. The transducer was attached to a 4 aluminum towbody suspended in front of the boat and deployed at a speed of approximately 3-4 knots. Transects were run on two nights and two days in late summer in each year such that they intersected the deepest portions of each lake. The returning acoustic signal was recorded on audio tape (until ~ 1989) or DAT tapes (from ~ 1989-1994), as well as on paper charts. The recorded signal was analyzed with the deconvolution program developed by C.S. Clay (Rudstam et al. 1987, Stanton and Clay 1986, Jacobson et al. 1990) and with the HADAS post processing package by Torfinn Lindem (Lindem 1993, Rudstam et al. 1988) to estimate fish densities, by size, for each discrete depth in the lake. Most of the information collected from 1981 to 1989 was collected without recording the gain setting on the audio tapes and some tapes were recorded with too low gain resulting in too high signal to noise ratios. This made post processing difficult, however some data could be recovered by using the target strength of the dominant fish species to scale the recordings. Lars Rudstam analyzed data prior to 1989 using target strength estimated from fish caught in gillnets to calibrate the sonar information. Data and information was published on Trout Lake for 1983 and 1985 (Jacobson et al. 1990), Trout and Muskellunge Lakes for 1981 (Rudstam et al. 1987), on Mendota for 1981 to 1989 (Rudstam et al. 1993) and expanded to 1991 in DeStasio et al. (1995). For Crystal Lake, Rudstam generated data from 1981-1988 while Hrabik analyzed information from 1989-1995 (Sanderson et al. 1999). In 1995, the Simrad EY-M echosounder ceased to work reliably. In 1996, the LTER project purchased an HTI Model 241 echosounder with a 120 kHz split beam configuration. This echosounder was deployed in the manner described above on (Allequash, Big Muskellunge, Crystal, Sparkling, Trout, Mendota, Monona, and Fish Lakes). Ecoscape post-processing software, produced by HTI, was used to post-process data. Data were archived in the output format from HTI sounder software v. 1.0 and raw acoustic signals were stored on digital audio tapes. Prior to post processing of all HTI data, however, the computer containing the Ecoscape software ceased to work. No computer was purchased to replace it and the analysis, in 1998-9, also ceased. However, all the raw acoustic information is archived on digital audio tapes and processed on the HTI sounder software output files. After the laptop that operated the HTI system failed, there were no funds offered to replace it. No information was collected in 2000 because there was no laptop. Thus, there have been two major changes in analysis methods over time. The first was a change in single beam methods from the C.S. Clays deconvolution method to T. Lindems HADAS system. Rudstam et al (1988) found the two methods comparable. The second change involved switching from single beam analysis to split beam, from a 70kHz frequency to 120kHz and from Simrad to HTI and later Biosonics. Rudstam et al. (1999a) compared the single beam HADAS analysis using 70kHz (Simrad EYorM, HADAS analysis), split beam 70kHz (Simrad EY500, EP500 analysis) and split beam 120 kHz (Simrad EY500, EP500 analysis) for rainbow smelt in Lake Erie. Differences in density estimates and average target strengths were not large although there was a bias in the HADAS approach to single beam derived average target strength of 0.8dB (Rudstam et al. 1999a). Rudstam et al (1999b) reviewed the single beam methods in general and Mason and Schaner (2001) has compared data from the Biosonics, Simrad, and HTI units for smelt in Lake Champlain. From 2001-2003, sonar data was collected on Trout, Sparkling and Crystal Lakes using a Biosonics DT-6000 Echosounder with a 120kHz split beam transducer (T. Hrabik). Post-processing was performed using Echoview (SonarData Inc.) analysis software. In 2004, a Biosonics DT-X echosounder with a 70 kHz split beam transducer was used on Trout and Sparkling Lakes (T. Hrabik). No information was collected on Crystal Lake (the generator made too much noise in 2003 and caused a response from Law Enforcement). The information collected by Hrabik between 2001 and 2004 is currently being analyzed to generate aggregated lake-wide and 200 m transect-level fish size and density estimates (which can be converted into biomass and biomass by species using gillnet information) as well as transect-level data stratified at a 1m vertical depth resolution.Data Correction:December 2013: an error was detected for data from Sparkling Lake for the year 2004. Erroneous data have been replaced with corrected data in the metadata version 10 and data version v3.January 2014: an error was detected for data from Trout Lake for the year 2012. Erroneous data have been replaced with corrected data in the medatadata version 11 and data version v4. Literature cited DeStasio, B. J., L. G. Rudstam, A. Haning, P. Soranno, and Y. Allen. 1995. An in situ test of the effects of food quality on Daphnia population growth. Hydrobiologia 307:221-230. Jacobson, P. T., C.S. Clay, and J.J. Magnuson. 1990. Size, distribution, and abundance of pelagic fish by deconvolution of single beam acoustic data. Rapp. P.-v. Reun. Cons. int. Explor. Mer 189:304-311. Lindem, T. 1983. Successes with conventional in situ determination of fish target strength. FAO Fish. Rep. 300:104-111. Lindem, T. 1990. Hydro acoustic data acquisition system HADAS. Instruction manual. Lindem data acquisition Lda, Oslo. Lindem, T., and D. A. Houari. 1988. Hydro acoustic data acquisition system HADAS. mimoegraphed report. Lindeman, R. L. 1942. The trophic dynamic aspect of ecology. Ecology 23:157-176. Mason, D. M., and T. Schaner. 2001. Final report to the Great Lakes Fisheries Commisison for the acoustics intercalibration exercise in 1999. Rudstam, L. G., C. S. Clay, and J. J. Magnuson. 1987. Density and size estimates of cisco, Coregonus artedii using analysis of echo peak a single transducer sonar. Canadian Journal of Fisheries and Aquatic Sciences 44:811-821. Rudstam, L. G., S. Hansson, T. Lindem, and D. W. Einhouse. 1999. Comparison of target strength distributions and fish densities obtained with split and single beam echo sounders. Fisheries Research 42:207-214. Rudstam, L. G., T. Lindem, and S. Hansson. 1988. Density and in situ target strength of herring and sprat: a comparison between two methods of analyzing single beam sonar data. Fisheries Research 6:305-315. Rudstam, L. G., T. Lindem, and G. LaBar. 1999. The single beam analysis. Pages 6-13 in E. Ona, editor. Methodology for target strength measurements (with special reference to in situ techniques for fish and micronekton). International Council for the Exploration of the Sea, Copenhagen. Sanderson, B. L., T. R. Hrabik, et al. 1999. Cyclic dynamics of a yellow perch (Perca flavescens) population in an oligotrophic lake: evidence for the role of intraspecific interactions. Canadian Journal of Fisheries and Aquatic Sciences 56: 1534-42. Stanton, T. K., and C. S. Clay. 1986. Sonar echo statistics as a remote-sensing tool: volume and seafloor. IEEE Journal of Oceanic Engineering OE-11:79-96.

Methods

The same sampling sites are used each year. All sampling occurs between the 3rd week of July and Labor Day. Sampling sites were chosen by random process in 1981 for the Northern lakes (Trout, Allequash, Sparkling, Crystal, and Big Muskellunge). Sites for Lake Mendota were chosen in 1981, and for the other Madison lakes (Monona, Fish, and Wingra) in 1995. All sites are identified with GPS coordinates, except on the bog lakes (Trout Bog and Crystal Bog) where nets are placed equal distances apart around the entire circumference of the lake in approximately the same locations each year.

Night seining is conducted on 6 seine sites per lake, each consisting of 100 meters of shoreline. Prior to 1997 this was subdivided into 3 seine hauls, each covering 33 meters. In 1997, seine hauls were reduced to 2 hauls of 33m each. The final section of the site is used as an alternate seine site in the event of difficulty in one of the first two hauls.
The seine used is 12.2 m long by 1.2 m deep, consisting of two 5.5 x 1.2 m wings surrounding a 1.2 x 1.2 x 1.2 m central bag. The wings are made of 6.4 mm stretch measure knitted delta-strength nylon mesh, and the bag is of 3.2 mm delta strength nylon mesh. The entire net is tarred. The two wings and the opening to the bag have weighted foot ropes and buoyed head ropes. An 8m length of rope is tied between the seine poles as a guide for the maximum spread of the seine.

A trammel net is set at two sites in each lake, and fished for approximately 24 hours at each site. The net is set on the bottom, along a line perpendicular to the shoreline and crossing the thermocline, with the shallow end at about 3m depth,. The trammel net used is 30.5 m long and 1.1 m deep. It consists of two outer nets of 170 mm square 32 kg test mesh multifilament nylon with an inner panel of 51 mm stretch mesh 9 kg test multifilament nylon. The three nets are connected at the leaded foot line and the buoyed head rope.

Fyke nets are deployed at six littoral sampling sites in each lake, and fished for approximately 24 hours. In Crystal Bog and Trout Bog lakes the fyke nets are suspended by placing floats on the hoops and frames to prevent the nets from sinking into the sediments. For the northern lakes, each fyke net is approximately 12 m long and consists of two rectangular steel frames 90 cm wide by 75 cm high and 4 steel hoops, all covered by 7 mm delta stretch mesh nylon netting. An 8 m long by 1.25 m deep leader net made of 7 mm delta stretch mesh nylon netting is attached to a center bar of the first rectangular frame (net mouth). The second rectangular frame has two 10 cm wide by 70 cm high openings, one on each side of the frame center bar. The four hoops follow the second frame. Throats 10 cm in diameter are located between the second and third hoops. The net ends in a bag with a 20.4 cm opening at the end, which is tied shut while the net is fishing. New nets of the same dimensions were purchased for the Northern Highland lakes in 2000. Fyke nets for the Madison lakes are 10 m long (including lead) with 1 rectangular aluminum frame followed by 2 aluminum hoops. The aluminum frame is 98 cm wide x 82 cm tall, and is constructed of 2.5 cm tubing, with an additional center vertical bar. The hoops are 60 cm in diameter and constructed of 5 mm diameter aluminum rod. The single net funnel is between the first and second hoops and is 20 cm in diameter. The lead is 8 m long and 1.25m deep, constructed from 7mm delta stretch mesh.

Crayfish traps are set on all lakes except the bog lakes (Crystal Bog and Trout Bog). Minnow traps are set only on the bog lakes. Prior to 1998, five traps were set at each fyke net site. Beginning 1998, three traps are set per site. Minnow traps and crayfish traps are set in shallow water (approx 1 m), 2 traps on one side, and 1 trap on the other side of the fyke net lead. Minnow traps are baited with 1 slice of bread, and crayfish traps with 120 g of beef liver. Traps are fished for approximately 24 hours. Crayfish are identified to species. Minnows caught in either crayfish or minnow traps are identified to species, and measured for total length. Minnow traps are galvanized steel two piece traps, 44.5 cm long by 30.5 cm maximum diameter with 2.5 cm diameter openings at the ends. The mesh size is 6.4 mm on a side. Crayfish traps are identical, but the opening hole of both sides of the trap has been forced to 5 to 7 cm. Crayfish sampling was terminated for the southern lakes in 2004 after it was determined that the catch per unit effort was too low (2 crayfish caught in 500+ traps)

Gill nets are set at the deepest point of all LTER lakes except Crystal Bog, Trout Bog, and Fish Lake. The nets are set for two consecutive 24 hour sets. The gill nets are a set of 7 nets, each in a different mesh size, hung vertically on foam rollers from the surface to the bottom of the lake, and chained together in a line. Each net is 4 m wide and 33 m long. From 1981 through 1990 the nets were multifilament mesh, in stretched mesh sizes of 19, 25, 32, 38, 51, 64, and 89 mm. In 1991, the multifilament nets were replaced with monofilament nets of the same sizes. Stretcher bars are installed at 10 meter intervals from the bottom to keep the net as rectangular as possible when deployed.

A boom style electrofishing system is used to sample the littoral zone fish community. Prior to 1997, four electrofishing transects were done on each lake. In 1997, the number of transects was reduced to 3. The same transects are used each year. Each transect consists of 30 minutes of current output, with the boat moving parallel to shore in 1-2 meters of water at a slow steady speed. We use the DC pulse system, with 240 volts at 3-5 amps. Transect lengths vary depending upon the size of the lake. If the end of a transect is reached before 30 minutes has elapsed, time is paused while the electrofisher loops back to the start of the transect. The transect is then repeated for the remaining time.

For all collecting methods, the fish are processed as follows. Each individual fish is identified to species. The total length of the fish is measured in mm, from nose to pinched tail. Prior to 1997, the weight of the first five fish of each species in each 10 mm size category was also measured, using Pesola spring balances. Starting in 1997, two fish are weighed for each species in each 5mm size category. A scale sample is collected from each yellow perch, rock bass, and cisco that is weighed. For gill net catches, the depth at which each individual is caught is also recorded.

Protocol Log. 1983: Discontinued fyke nets and trammel nets on Lake Mendota until 1995. 1984: Discontinued crayfish on Lake Mendota until 1995. Only gillnet and seines on Lake Mendota.1995: Resumed sampling Lake Mendota with the full suite of sampling gear. 1995: Began sampling Lakes Wingra, Monona, and Fish. 1997: Two fish are weighed for each fish species in each 5mm size category. Previously, five fish were weighed for each fish species in each 10mm size category. 1997: Data recording switched from manual field sheets to an electronic system. 1997: Changed from 4 to 3 electrofishing runs per lake. 1997: Changed from 18 to 12 seine hauls per lake. 1998: Changed from 30 to 18 crayfish or minnow traps per lake. 2004: Discontinued crayfish or minnow traps on southern lakes. 2020: Fish sampling very limited due to pandemic. 2021 discontinued all night seining.

DATA MODIFICATIONS
Prior to 2018, gill net data had been standardized to a 24-hour sampling period. This is no longer the case, and catch numbers for all years have been recomputed to reflect the number of fish actually caught.
2018-01-18: Species names ('spname') added in 2012 had space characters appended to the end of the name. These spaces have been removed. The occasional appearance throughout the data set of species name 'SUNFISH' and 'LARVALSUNFISH' have all been changed to 'UNIDSUNFISH'.

Methods

see abstract.

Methods

FISH SAMPLING TECHNIQUESThe techniques used to sample the fish and estimate the population density in the cascadelakes, vary according to the species and life-stage of interest. The following techniquesfor the different fish populations have been used from 1984 to present, except whennoted.1. Minnows (Dace, Mudminnows, Sticklebacks and assorted small cyprinids) andBass (young-of-year):The gear most used to sample these small-bodied species is the minnow trap. Thetraps are commercially available under the name Gee s Minnow Trap. They aremade of 1or4&quot; galvanized hardware cloth with approximately 1&quot; openings in eitherend. The only modification made to the commercial trap, is treatment with acidprior to use to remove the shine of the new trap. Shiny traps have been found tobe less effective. Twenty-four minnow traps are set in the littoral zone and 18 inthe pelagic zone of each lake. The littoral traps are set from stakes approximatelyuniformly spaced around the lake at depths of .5 m and on the bottom alternately.The pelagic traps are set at 1 and 3 m across the deepest portion of the lake on asingle transect with 9 stations (one 1 m and one 3 m trap at each station). Thetraps are set bi-weekly for 24 hr. All fish are counted and identified to species.The traps are normally set unbaited. Bait (bread) is used when large numbers ofminnows must be caught, such as for a Delury estimate (Ricker, 1975).A subsample of approximately 400 individuals is measured. These 400 fish areanesthetized in small batches with MS-222. The anesthetized fish are placed on aclipboard covered with a sheet of transparency plastic. The nose of the minnow isplaced against a retaining board and a hole is punched in the plastic at the end ofthe minnow s tail. The distance from the edge of the plastic to hole is measuredback at the lab to obtain total length in millimeters.Both mark-recapture and Delury population estimation are used to estimate theabundance of minnows. With mark-recapture, a large subsample, greater than1000individuals, from a minnow-trap capture are finclipped and released. Minnowtraps are then reset after waiting at least 1 but not more than 7 days. Thepopulation is then estimated using the ratio of marked to unmarked fish caught inthe second set. The Delury estimate is done by depleting the population usingrepeated minnow trapping and recording the catch and cumulative catch. Theminnows are held in floating net boxes at densities of 1000-2000 per cubic meteruntil at least four trap sets have been made. The population is estimated by theintercept of the regression between catch and cumulative catch (the level ofcumulative catch where catch equals zero). The Delury and mark-recaptureestimates provides an independent population estimate to correlate the catch-per132unit-effort (CPUE) of the regular minnow-trapping with known populationdensities.1332) Bass and perch (age 1plus and older):The larger fishes are sampled for population estimation twice each year, once inmid-May and once in mid-August. The primary technique used is nightelectrofishing with mark-recapture population estimation.A 16 foot Cofelt electrofishing boat, with dual booms (3 4-ft electrodes perboom), is used. Electroshocking is done largely perpendicular to shore,shocking from approximately 3 meters water depth to the shore. DC current isused to minimize damage to the fish. 600 volts provides adequate current, 2-6amps, to stun the fish.All fish are placed in a live-well on board the shock boat and are taken to ashore station for processing. On shore, the first 25 fish of each species arestomach pumped for gut analysis. Scales are also taken from a subsample of thefish for age analysis. All fish are identified to species, counted, measured (totallength in millimeters), and weighed with either a Pesola spring-scale or anOhaus electronic pan balance. If the spring-scale is used then the fish is simplyheld by the lip with the clip on the scale; if the electronic scale is used the fish iswrapped in a wet cloth to restrain the fish and the fish and cloth are weighedtogether. The weight of the cloth is removed by taring the scale with the clothprior to weighing the fish.If a markorrecapture estimation of the population is to be done, all fish sampledon the first night of electrofishing are marked. The fish are tagged withindividually numbered anchor tags (Wydoski and Emery, 1983) if the fish isgreater than 150mm total length and has not been previously tagged. If the fishis smaller than 150mm, the dorsal lobe of the caudal fin is clipped. The markedfish are then placed in a holding net until the first sampling is complete. Thefish are released at the end of the first night of electrofishing. To increase thepower of the mark-recapture technique, the number of marked fish is increasedby angling and marking fish on the day prior to electroshocking at night forrecapture. The population is sampled again the following night to estimate theratio of marked to unmarked fish. For the Delury estimation, fish are removedfrom the lake using several days of sampling effort using both angling andelectroshocking.3) Scale Samples:Scale samples are taken at least once a year, from at least 50 randomly selectedfish of each species. Large fish are usually sampled for scales when they arecaught. At least 5 scales are taken from each fish from the area below the originof the dorsal fin and above the lateral line. Scales are permanently mounted ona plastic slide later for aging and individual growth determination (Summerfeltand Hall, 1987).1344) Larval Perch (and other pelagic larvae), 1989-present:Two techniques are used to sample pelagic fish larvae: purse seining, and sonar.a. Purse seining is a method of enclosing a volume of water in the pelagiczone with a net and filtering that water to obtain the larval fish. The netdesign and technique are described in Evans and Johannes (1988). Thenet used in the Cascade project is 33 meters long and 6 meters deep, madeof polyester net material with 1.6mm openings and dyed green.b. Sonar is used in conjunction with purse seining to obtain the sizefrequency,species composition, and spatial distribution of icthyoplankton.The Cascade project uses both 70 and 200 khz sonar. The transducer istowed approximately 20cm under the surface. The technique is outlined inThorne (1983). The HADAS acoustics processing hardware and softwareis used to analyze the recorded signal (see Rudstam, 1988, for adescription of the analysis).STATISTICAL POPULATION ESTIMATIONThe two techniques used in the Cascade project to estimate population density are themodified Peterson mark-recapture and Delury estimations (Ricker 1975).a. Mark-recapture is used for populations that are not being intentionallydepleted in a lake such as the bass population in Paul Lake.b. Delury estimates are used when a population is being removed from a lakesuch as for the bass in Peter Lake in the fall of 1989 or for minnows whichare easily handled.135REFERENCES:Evans, D.O. and P.R. Johannes. 1988. A bridle-less trawl and fine-mesh purse seine forsampling pelagic coregonine larvae with observations of the spatial distributionand abundance. Ontario Fish. Tech. Rep. no 27:1-19.Ricker, W.E. 1975. Computation and interpretation of biological statistics of fishpopulations. Department of the Environment, Fisheries and Marine Service,Fisheries Research Board of Canada Bulletin 191, Ottawa, Canada.Rudstam, Lars G. 1988. Patterns of zooplanktivory in a coastal area of the northernBaltic proper. Doctoral thesis at the University of Stockholm.Summerfelt, R.C. and G.E. Hall. 1987. Age and Growth of Fish. Iowa State UniversityPress, Ames. Iowa.Thorne, R.E. 1983. Hydroacoustics. pp. 239-260. In: L.A. Nielsen and D.L. Johnson ed.Fisheries Techniques. American Fisheries Society, Bethesda, Maryland.Wydoski, R. and L. Emery. 1983. Tagging and Marking. pp. 215-237. In: L.A. Nielsenand D.L. Johnson ed. Fisheries Techniques. American Fisheries Society,Bethesda, Maryland.136

Methods

Fish were collected by beach seining, hook and line angling, and minnow traps. Commonly captured species were largemouth bass, bluegill, yellow perch, rock bass, and black crappie. Population Estimates: Chapman-modified continuous Schnabel mark-recapture population estimates were conducted on each basin of Little Rock and Camp lakes annually. Adult population estimates for largemouth bass, yellow perch, rock bass, and black crappie were calculated for Little Rock Lake during 2001-2006. All fish were captured by hook and line angling, minnow traps, and beach seining. Adult population estimates for largemouth bass and bluegill were calculated for Camp Lake during 2002-2006. All fish were captured by hook and line angling and beach seining. Fish Length/Weight Tag data: Length, weight, and mark data was recorded for all fish used to collect diet information. Diet information was collected from up to 15 individuals of each species biweekly May-September using gastric lavage. Diet information was collected from largemouth bass, yellow perch, rock bass, and black crappie in Little Rock Lake from 2001-2005 and 2007 - 2009. Diet information was collected from largemouth bass and yellow perch in Camp Lake from 2002-2005. Fish Length Tag data: Length and mark data was recorded for all fish used to calculate the mark-recapture population estimates. Length and the mark were recorded from all fish captured in Little Rock and Camp lakes from 2001-2006. Length and mark data exists for all fishes collected in Little Rock Lake from 2001-2006 and 2007 - 2009. Fish species from Little Rock include largemouth bass, yellow perch, rock bass, and black crappie. Length and mark data exists for all fishes collected in Camp Lake from 2002-2006. Fish species from Camp Lake include largemouth bass, yellow perch, and bluegill. All fish were captured by beach seining, hook and line angling, and minnow traps. Minnow trap CPUE: Minnow traps were the most effective gear for capturing yellow perch on Little Rock Lake. Standardized minnow trapping was conducted on both basins of Little Rock Lake in 2003-2005. In 2003, 10 minnow traps in each basin were deployed biweekly and picked twice per week. In 2004-2005, 20 minnow traps in each basin were deployed biweekly and picked twice per week. Catch per unit effort was calculated as catch of yellow perch per trap. Age Growth Rates: Growth rates were calculated for a subset of fish collected from Little Rock Lake (2001-2004) and Camp Lake (2002-2005). Back-calculated growth rates from five fish from every 10 mm size increment were examined. In the process, age was determined from scale samples and length at each annulus was back-calculated. Size-specific growth rates were calculated based on the relationship between fish length at age and ln transformed growth rate at age. Back-calculated growth information was assessed from largemouth bass, yellow perch, rock bass, and black crappie in Little Rock Lake. Back-calculated growth information was assessed from largemouth bass and bluegill in Camp Lake.

Methods

Setting NetsSet nets in areas of high catch first, moving clockwise around the lake.GPS location of netRecord dates in that locationNumber nets consecutively from first net set. (Nets do not need to be pulled in order they were set.) If a net is moved, keep the same number and add an a, b, c, etc after.Sketch net location on a map with the net number (keep with In-Boat data sheets)Pulling NetsTake lake map with net numbers and In-Boat data sheetRecord date, time, collectors namesAt each net, record net number, number of bags and any comments (note anything unusual)For a zero catch&hellip; note if the net was fishing (tipped over, twisted, etc). If there were no problems write NORMAL SET.Try to set the net in exactly the same location. (Over burlap if applicable)Data CollectionIf there is not enough time, please follow this order for priority of data collection.Daily CatchUse Daily Catch sheetRecord date, net number, bag number, number of bags from that netWeigh bags in kilograms. Record.Note if fish were kept for sex determination, length &ndash; weight or scales and the number kept.Sex ratioUse Sex sheetRandomly select 2 nets. Sample 50 fish from each net.Record date and net numberWeigh two empty buckets and record weight.Separate fish by sex. Try not to squeeze out eggs/sperm.Count number of males and females. Record.Weigh buckets with males or females in them. Record.Length WeightUse Length Weight sheetSelect a random net and sample 30 fish from itRecord date, net number, if fish were frozenRecord length, weight and sex.Compare to scale sheet. Collect scale sample if category is not filled. Pull scales from behind the dorsal fin. Note on data sheet that scales were taken. Scale envelopes should have date, length, weight, net number and sex of fish on them.

Methods

Littoral Zone Surveys: Littoral habitat, fish and macrophyte surveys were performed at eight sites within each of the 55 lakes. The sites were chosen by randomly selecting two points per compass quadrant of each lake. Each year littoral habitat surveys were conducted in June, fish surveys in July and macrophyte surveys in August.Littoral fish were sampled in July of each year, along the shallow areas (water depth greater than 0 and less than2 m) adjacent to the riparian plots. Night electroshocking and crayfish and minnow traps were used to catch fish and crayfish. All species were identified and counted.