US Long-Term Ecological Research Network

North Temperate Lakes LTER: Macrophyte Biomass in Trout Lake Summary 1983 - current

Abstract
These data are collected to document and characterize the submersed macrophytes of Trout Lake, to evaluate the long-term stability of this component, and to interface with investigations of other compartments of the ecosystem. Four sites along the shoreline of Trout Lake have been sampled annually in August along permanent line transects. This dataset includes biomass per m2 for individual species summarized by depth along the transect. Derived data include the mean and standard deviation of macrophyte biomass. These data are useful in determining the annual variability of the submersed macrophytes and providing information on the effects of the invasion of an introduced crayfish. Sampling Frequency: annually during summer Number of sites: 4
Core Areas
Dataset ID
25
Date Range
-
Maintenance
ongoing
Metadata Provider
Methods
Sites are designated according to the NTL numbering scheme established for the shoreline of the south basin of Trout Lake and its islands. The four sites (Trout-07, 46.01809769, -89.65571661; Trout-31, 46.0430698, -89.67157974; Trout-50, 46.01729465, -89.69461296; Trout-56, 46.01921135, -89.6813004) used by the macrophyte component are also used in the NTL fish and crayfish sampling. Five replicate quadrats (0.25 M2) are harvested for all above ground biomass at each site at each of three nominal depths: 1.5 M, 2.5 M and 4 M. Samples are removed along a line parallel to shore - located midway between sites for cover estimates. Four sites with 3 depths and 5 replicates yields 60 samples. In the lab, samples are separated by species and are dried and weighed. From 1989 to 2008 plants were placed in labeled paper bags oven dried, and weights recorded. Biomass weights were determined by weighing dried plants in paper bags and using an average tare for the bags. Consequently, values in the data base can be negative and should be considered as present in very small amounts.
Pre-1987 Data. In 1987, permanent line transects were established at each of the sites. Biomass samples and line transects observed before 1987 were set by more general descriptions at the site and were not identical year to year.
Publication Date
Short Name
NTLMP05
Version Number
25

North Temperate Lakes LTER: Macrophyte Biomass - Madison Lakes Area 1995 - current

Abstract
Macrophytes are sampled in Lakes Mendota, Monona, Wingra, and Fish. In the Madison area surveys are conducted from a boat at stations located at depths from 1 to 4 meters at 0.5-m intervals along transects perpendicular to the lake shoreline. Macrophyte total plant mass and the total filamentous algae mass is measured as fresh weight by standardized rake method. Sampling Frequency: annually during summer (June - August) Number of sites: 4
Core Areas
Dataset ID
24
Date Range
-
Maintenance
ongoing
Metadata Provider
Methods
Aquatic macrophytes are sampled from a boat at stations located at depths from 1 to 4 meters at 0.5-m intervals along transects perpendicular to the lake shoreline of the four primary study lakes in the Madison area (Lakes Mendota, Monona, and Wingra, and Fish Lake) from June to August. A weighted, double-headed garden rake is cast off the front left, front right, rear left, and rear right of the boat and then dragged approximately 2 meters across the bottom by means of an attached line. The total plant mass and the total filamentous algae mass in each tow is measured. To the maximum extent possible, water is squeezed from the plants to minimize the amount of water present in the final weight. Weights are recorded in the boat using field scales. Weights from the 4 rake casts at each station can be averaged to compute overall average weights for plant mass and for filamentous algae mass at the station.
Detailed Macrophyte Sampling description.
Using the site book and the depth measuring pole, move to the 1 meter depth mark and throw both anchors. From the Macrophyte Depth Table, find the distance to throw out the rake and the meter mark that the line should be drawn to. The table is calculated to determine the starting and ending meter marks to draw in the line to allow the rake to drag 2 meters on the lake bottom. Pull the rake quickly out of the water. If a significant amount of dirt has been brought up with the plants (i.e. the weight of the dirt will add significantly to the total weight), wash the plants. Depending on the volume of the plants, wash them either by keeping them in your hands and dunking them in the lake or by putting them in a bucket with drain holes. Separate the filamentous algae from the rest of the plant material. Squeeze out as much water as possible (it may be necessary to divide up the plant material into portions to effectively squeeze out the water). Weigh the plant material (minus the filamentous algae) and record the total weight. Weigh the filamentous algae and record the weight. Repeat the above steps until 4 rake tosses have been thrown. Move to the next half-meter depth. Macrophytes are collected at each half-meter water depth from 1 meter to 4 meters.
Publication Date
Short Name
NTLMP04
Version Number
27

North Temperate Lakes LTER: Macrophyte Biomass - Trout Lake 1983 - current

Abstract
These data are collected to document and characterize the submersed macrophytes of Trout Lake and to evaluate their long-term dynamics and interactions with other compartments of the ecosystem. Four sites along the shoreline of Trout Lake have been sampled annually in August along permanent line transects. This dataset includes biomass per m^2 for individual species at three depths along the transect. These data are useful in determining the annual variability of the submersed macrophytes and providing information on the effects of the invasion of an introduced crayfish. Sampling Frequency: annually during summer Number of sites: 4
Core Areas
Dataset ID
21
Date Range
-
Maintenance
ongoing
Metadata Provider
Methods
Sites are designated according to the NTL numbering scheme established for the shoreline of the south basin of Trout Lake and its islands. The four sites (Trout-07, 46.01809769, -89.65571661; Trout-31, 46.0430698, -89.67157974; Trout-50, 46.01729465, -89.69461296; Trout-56, 46.01921135, -89.6813004) used by the macrophyte component are also used in the NTL fish and crayfish sampling. Five replicate quadrats (0.25 M2) are harvested for all above ground biomass at each site at each of three nominal depths: 1.5 M, 2.5 M and 4 M. Samples are removed along a line parallel to shore - located midway between sites for cover estimates. Four sites with 3 depths and 5 replicates yields 60 samples. In the lab, samples are separated by species and are dried and weighed. From 1989 to 2008 plants were placed in labeled paper bags oven dried, and weights recorded. Biomass weights were determined by weighing dried plants in paper bags and using an average tare for the bags. Consequently, values in the data base can be negative and should be considered as present in very small amounts.
Pre-1987 Data. In 1987, permanent line transects were established at each of the sites. Biomass samples and line transects observed before 1987 were set by more general descriptions at the site and were not identical year to year.
Publication Date
Short Name
NTLMP01
Version Number
26

North Temperate Lakes LTER: Fish Lengths and Weights 1981 - current

Abstract
Data are collected annually to enable us to track the fish assemblages of eleven primary lakes (Allequash, Big Muskellunge, Crystal, Sparkling, Trout, bog lakes 27-02 [Crystal Bog] and 12-15 [Trout Bog], Mendota, Monona, Wingra and Fish). Sampling on Lakes Monona, Wingra, and Fish started in 1995; sampling on other lakes started in 1981. Sampling is done at six littoral zone sites per lake with seine, minnow or crayfish traps, and fyke nets; a boat-mounted electrofishing system samples four littoral transects. Vertically hung gill nets are used to obtain two pelagic samples per lake from the deepest point. A trammel net samples across the thermocline at two sites per lake. In the bog lakes only fyke nets and minnow traps are deployed. Parameters measured include species-level identification and lengths for all fish caught, and weight and scale samples from a subset. Dominant species vary from lake to lake. Perch, rockbass, and bluegill are common, with walleye, large and smallmouth bass, northern pike and muskellunge as major piscivores. Cisco have been present in the pelagic waters of four lakes, and an exotic species, rainbow smelt, is present in two. The bog lakes contain mudminnows.
The only sampling done in 2020 were a single gill-netting replicate in Sparkling, Crystal, and Trout lakes.
Sampling Frequency: annually Number of sites: 11
Core Areas
Dataset ID
6
Date Range
-
LTER Keywords
Maintenance
ongoing.
Metadata Provider
Methods
SAMPLING SITES The same sampling sites are used each year. All sampling occurs between the 3rd week of July and Labor Day. Lakes are sampled in the following order: Trout, Allequash, Crystal, Big Muskellunge, Sparkling, Crystal Bog, Trout Bog, Wingra, Fish, Monona, Mendota. Sites for fyke nets, trammel nets and night seining sites were chosen by random process in 1981 for the Northern Highland State Forest lakes (Trout, Big Muskellunge, Allequash, Crystal, Sparkling). Sites for Lake Mendota were chosen in 1981, and for the other Madison lakes (Monona, Fish, and Wingra) in 1995. In 1998, all the Northern Highland lake sampling sites were recorded and archived as GPS coordinates. In 1999, all the Madison lake sites were recorded and archived as GPS sites. Prior to 1998 and 1999, fyke and trammel net sites were found each year by reference to lake maps, local landmarks, and stake locations. Gill nets are placed near the deep-hole, which is marked by a buoy and GPS coordinates, on each lake. In the bog lakes (Trout Bog and Crystal Bog), which are sampled with only fyke nets and minnow traps, there are no fixed sites; nets are placed equal distances apart around the entire circumference of the lake in approximately the same locations each year. NIGHT SEINING Night seining is conducted to achieve relative abundances of small fish species such as minnows, darters, sculpin, and young gamefish species on a yearly basis. Seining is most effective on small fish at night, due to reduced net avoidance, and is one of the most effective methods of catching small fish species. 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. The seine is pulled via two PVC or steel poles on either end of the seine. Prior to 1997, seine sites consisted of 100 meters of shoreline. This was subdivided into 3 seine hauls, each covering 33 meters. Stakes were placed to mark the beginning and end of each haul, with the first stake lettered A and the fourth (final) stake lettered D. In 1997, seine hauls were reduced to 2 hauls of 33m each. The final 34m of the 100m site (stakes C-D) is now used as an alternate seine site in the event of difficulty (snag, twisted net) in one of the first two hauls. Our convention is that the first haul (identified as "site number -1") is the one segment at the left end of the site, as one faces the site from the lake. The day crew working the lake will have marked the location of these stakes using green 12-hour chemical light sticks. There are 6 seine sites per lake for a total of 18 hauls per lake prior to 1997; starting in 1997, there are 12 hauls per lake. The seine crew approaches the site from the lake by boat in such a way as not to pass over the area to be seined. The seine is deployed using as little light as possible. An 8m length of rope is tied between the poles as a guide for the maximum spread of the seine. Two people, working 8 meters apart when possible, pull the seine on a course parallel to the shore line. The outside or deep person should be 8m from the shallow person (max rope length) or as deep as they can be without overtopping their waders (just below chest height). The inside or shallow person keeps as close to shore as possible without steeping onto dry land. When the shallow person is about 8 meters from the end of the haul heorshe moves very slowly, allowing the deep person to swing around toward the chemical light stick; both seiners should reach the light at the same time. The seine is quickly landed by crossing the poles and drawing the lead line together. The lead line is kept on the lake bottom while the wings are drawn in. When the bag reaches the poles it is picked up by the 4 corners. Fish are collected from the bag and processed before the crew goes on to the next haul. TRAMMEL NET The trammel net is used to sample fish species present near the bottom at the thermoclineorsubstrate interface. This area is utilized by a number of fish species, and is an important area of the lake due to the large change in temperature in a relatively short distance. As in the terrestrial environment, the thermocline acts as an ecotone and several fish species which require very different physical environments may exist in relatively close proximity. So achieving yearly fish abundances in this habitat is also important in determining long term trends in fish abundances. 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. The trammel net is set on the bottom, along a line perpendicular to the shoreline and crossing the thermocline. This can generally be accomplished by setting the shallow end in about 3 meters of water, and running the net out perpendicular to shore. Fish are picked out of the trammel net as it is brought back into the boat. The trammel net is set by the day crew at two sites in each lake, and fished for approximately 24 hours at each site. FYKE NETS Fyke netting is a very common method of sampling a wide size range of fishes which use littoral zone habitat. At different times of the day andoror season, many different fish species utilize the littoral zone area for feeding, digesting, and mating purposes. Sampling the abundances of fish species in this area, thus, is also very important in determining yearly changes in fish abundances. To monitor yearly changes in littoral fish abundances, fyke nets are deployed at six sampling sites in all 11 LTER study lakes. A separate set of three fyke nets of similar dimensions are used for the Northern Highland lakes and the Madison lakes. For the Northern Higland 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 s 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 has the dimensions 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. Each fyke net is set in shallow water perpendicular to shore such that the net mouth is covered by about 1 meter of water when possible. When the net is properly set, the lead is perpendicular to shore, vertical and not twisted, the mouth of the net is upright and facing shore, and all the hoops are upright. When the net is pulled in, the hoops and frames are gathered together and lifted into the boat. The net is positioned over a live well with the net mouth upward. One frame at a time is lifted and any fish present are shaken down into the next chamber, until all the fish are in the bag, which is emptied into the live well. Three fyke net sites are set per day (for two days), each with a single net in the middle of a 100m site, for a total of 6 fyke net sites per lake. Due to the soft bottom, and small size of the bog lakes, minnow traps and fyke nets are the only gear used to sample the fish community of these systems. The fyke nets are suspended by placing floats at the apex of each hoop, and on the top of the opening frames. This is done to prevent the nets from sinking into the soft sediments at the bottom of the bogs. CRAYFISH AND MINNOW TRAPS There have been introductions of exotic crayfish species in recent years into many north temperate lakes. Monitoring yearly abundances of crayfish species is important in determining the status and extent of the invasions. 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. Starting in 1998, three traps are set per site. Thus, prior to 1998, thirty traps were set on each lake (covering 6 sites.) As of 1998, 18 traps are set on each lake. 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 per trap to attract minnows inhabiting the bogs. Crayfish traps are baited with 120 g of liver. Traps are fished for approximately 24 hours . Crayfish are identified to species and returned to the lake. Minnows caught in either the crayfish or minnow traps are identified to species, measured for total length. Minnow traps used 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. GILL NETS In most lakes, there are species of fish which inhabit the pelagic (open water) zone. These fish species can have a large impact on lake ecosystem dynamics when they occur in abundance. To monitor yearly changes in the abundance of pelagic fish species, we sample the deep basin of eight of the LTER lakes with vertical gill nets. Our gill nets are a set of 7 nets, each in a different mesh size, hung vertically from foam rollers, 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. One side of the net is marked in meters from top to bottom. Stretcher bars have been installed at 5 meter intervals from the bottom to keep the net as rectangular as possible when deployed. The bottom end is weighted with a lead pipe to quicken the placement of the net and to maintain the position of the net on the bottom. 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 nets are set in a straight line, each connected to the next, and anchored at each end of the line. Once the nets are in position, they are unrolled until the bottom end reaches the bottom, and then tied off to prevent further unrolling. The nets are pulled by placing each net onto a pair of brackets attached to the side of the boat and rolling the net back onto its float; the fish are picked out as the net is brought up, placed in tubs according to depth. The fish are processed when the net is completely rolled up and before it is redeployed. ELECTROFISHING We use a boom style electrofishing system 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. Two crew members in the bow of the boat dip up all stunned fish, placing them in the live well for processing at the end of each transect. Transect lengths vary depending upon the size of the lake. If the end of a transect is reached before 30 minutes has elpased, time is paused while the electrofisher loops back to the start of the transect. The transect is then repeated for the remaining time. In 1999, dip nets were standardized to 10 foot poles attached to 18in. x 20in. tear drop shaped hoops. The nets are made of 7 mm stretch mesh. PROCESSING THE CATCH For all collecting methods, the fish are processed as follows. Each individual fish is identified to species. If it cannot be positively identified, after it is processed, it is preserved in 10percent buffered formalin or 95percent ethanol for later identification. The total length of the fish (measured from nose to end of caudal fins pinched together) is measured in mm. Prior to 1997, the weight (g) of the first 5 fish of each species in each 10 mm size category was also measured, using the appropriate Pesola spring balance (fish weight registering in the middle range of scale). A tally sheet was used to record how many fish in each size category had been measured. Starting in 1997, 2 fish are weighed for each fish species in each 5mm size category. Also in 1997, data recording switched to an electronic system which tallied measured fish. For yellow perch, rock bass, and cisco, a scale sample is collected from each weighed fish. This is removed from the left side of the fish, above the lateral line and below the origin of the dorsal fin. Scale samples are stored in scale envelopes and labeled with a unique ID number, the date the scale was taken, a lake ID number, the species code, land length and weight. For gill net catches, the depth at which each individual is caught is also recorded. Fish from all gear (except gillnets) are held in live wells during processing. Fish are sorted by species into buckets, processed as quickly as possible, and returned to the lake. Fish from the gillnets are very rarely alive. If alive, they are usually badly damaged when the nets are raised. PROTOCOL CHANGES 1983 Discontinued fykenets 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 full suite of sampling gearr 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</p>
Short Name
NTLFI01
Version Number
29

North Temperate Lakes LTER: Fish Length Frequency 1981 - current

Abstract
This data set is a derived data set based on fish catch and length data. Data are collected annually to enable us to track the fish assemblages of eleven primary lakes (Allequash, Big Muskellunge, Crystal, Sparkling, Trout, bog lakes 27-02 [Crystal Bog] and 12-15 [Trout Bog], Mendota, Monona, Wingra and Fish). Sampling on Lakes Monona, Wingra, and Fish started in 1995; sampling on other lakes started in 1981. Sampling is done at six littoral zone sites per lake with seine, minnow or crayfish traps, and fyke nets; a boat-mounted electrofishing system samples three littoral transects. Vertically hung gill nets are used to obtain two pelagic samples per lake from the deepest point. A trammel net samples across the thermocline at two sites per lake. In the bog lakes only fyke nets and minnow traps are deployed. Parameters measured include species-level identification and lengths for all fish caught, and scale samples and weight from a subset. Derived data sets include species richness, catch per unit effort, and size distribution by species, lake, and year. Dominant species vary from lake to lake. Perch, rockbass, and bluegill are common, with walleye, large and small mouth basses, northern pike and muskellunge as major piscivores. Cisco have been present in the pelagic waters of four lakes, and the exotic species, rainbow smelt, is present in two. The bog lakes contain mudminnows. Sampling Frequency: annually Protocol used to generate data : Gill net data have been standardized to a 24-hour sampling period. Assumptions used in the standardization are available from the investigators. Day seines were only used in 1981 and have been eliminated from this data set to make sampling effort across years comparable. The number of fish caught in each five mm length interval (0<length<5, 5<=length<10, etc.) have been summed over gear. In cases in which only a random subsample of fish were measured, the unmeasured fish have been assigned to the length categories based on the proportions in length categories for the measured fish of the subsample.
The only sampling done in 2020 were a single gill-netting replicate in Sparkling, Crystal, and Trout lakes.
Number of sites: 11
Core Areas
Dataset ID
8
Date Range
-
LTER Keywords
Maintenance
ongoing
Metadata Provider
Methods
SAMPLING SITES The same sampling sites are used each year. All sampling occurs between the 3rd week of July and Labor Day. Lakes are sampled in the following order: Trout, Allequash, Crystal, Big Muskellunge, Sparkling, Crystal Bog, Trout Bog, Wingra, Fish, Monona, Mendota. Sites for fyke nets, trammel nets and night seining sites were chosen by random process in 1981 for the Northern Highland State Forest lakes (Trout, Big Muskellunge, Allequash, Crystal, Sparkling). Sites for Lake Mendota were chosen in 1981, and for the other Madison lakes (Monona, Fish, and Wingra) in 1995. In 1998, all the Northern Highland lake sampling sites were recorded and archived as GPS coordinates. In 1999, all the Madison lake sites were recorded and archived as GPS sites. Prior to 1998 and 1999, fyke and trammel net sites were found each year by reference to lake maps, local landmarks, and stake locations. Gill nets are placed near the deep-hole, which is marked by a buoy and GPS coordinates, on each lake. In the bog lakes (Trout Bog and Crystal Bog), which are sampled with only fyke nets and minnow traps, there are no fixed sites; nets are placed equal distances apart around the entire circumference of the lake in approximately the same locations each year. NIGHT SEINING Night seining is conducted to achieve relative abundances of small fish species such as minnows, darters, sculpin, and young gamefish species on a yearly basis. Seining is most effective on small fish at night, due to reduced net avoidance, and is one of the most effective methods of catching small fish species. 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. The seine is pulled via two PVC or steel poles on either end of the seine. Prior to 1997, seine sites consisted of 100 meters of shoreline. This was subdivided into 3 seine hauls, each covering 33 meters. Stakes were placed to mark the beginning and end of each haul, with the first stake lettered A and the fourth (final) stake lettered D. In 1997, seine hauls were reduced to 2 hauls of 33m each. The final 34m of the 100m site (stakes C-D) is now used as an alternate seine site in the event of difficulty (snag, twisted net) in one of the first two hauls. Our convention is that the first haul (identified as "site number -1") is the one segment at the left end of the site, as one faces the site from the lake. The day crew working the lake will have marked the location of these stakes using green 12-hour chemical light sticks. There are 6 seine sites per lake for a total of 18 hauls per lake prior to 1997; starting in 1997, there are 12 hauls per lake. The seine crew approaches the site from the lake by boat in such a way as not to pass over the area to be seined. The seine is deployed using as little light as possible. An 8m length of rope is tied between the poles as a guide for the maximum spread of the seine. Two people, working 8 meters apart when possible, pull the seine on a course parallel to the shore line. The outside or deep person should be 8m from the shallow person (max rope length) or as deep as they can be without overtopping their waders (just below chest height). The inside or shallow person keeps as close to shore as possible without steeping onto dry land. When the shallow person is about 8 meters from the end of the haul heorshe moves very slowly, allowing the deep person to swing around toward the chemical light stick; both seiners should reach the light at the same time. The seine is quickly landed by crossing the poles and drawing the lead line together. The lead line is kept on the lake bottom while the wings are drawn in. When the bag reaches the poles it is picked up by the 4 corners. Fish are collected from the bag and processed before the crew goes on to the next haul. TRAMMEL NET The trammel net is used to sample fish species present near the bottom at the thermoclineorsubstrate interface. This area is utilized by a number of fish species, and is an important area of the lake due to the large change in temperature in a relatively short distance. As in the terrestrial environment, the thermocline acts as an ecotone and several fish species which require very different physical environments may exist in relatively close proximity. So achieving yearly fish abundances in this habitat is also important in determining long term trends in fish abundances. 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. The trammel net is set on the bottom, along a line perpendicular to the shoreline and crossing the thermocline. This can generally be accomplished by setting the shallow end in about 3 meters of water, and running the net out perpendicular to shore. Fish are picked out of the trammel net as it is brought back into the boat. The trammel net is set by the day crew at two sites in each lake, and fished for approximately 24 hours at each site. FYKE NETS Fyke netting is a very common method of sampling a wide size range of fishes which use littoral zone habitat. At different times of the day andoror season, many different fish species utilize the littoral zone area for feeding, digesting, and mating purposes. Sampling the abundances of fish species in this area, thus, is also very important in determining yearly changes in fish abundances. To monitor yearly changes in littoral fish abundances, fyke nets are deployed at six sampling sites in all 11 LTER study lakes. A separate set of three fyke nets of similar dimensions are used for the Northern Highland lakes and the Madison lakes. For the Northern Higland 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 s 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 has the dimensions 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. Each fyke net is set in shallow water perpendicular to shore such that the net mouth is covered by about 1 meter of water when possible. When the net is properly set, the lead is perpendicular to shore, vertical and not twisted, the mouth of the net is upright and facing shore, and all the hoops are upright. When the net is pulled in, the hoops and frames are gathered together and lifted into the boat. The net is positioned over a live well with the net mouth upward. One frame at a time is lifted and any fish present are shaken down into the next chamber, until all the fish are in the bag, which is emptied into the live well. Three fyke net sites are set per day (for two days), each with a single net in the middle of a 100m site, for a total of 6 fyke net sites per lake. Due to the soft bottom, and small size of the bog lakes, minnow traps and fyke nets are the only gear used to sample the fish community of these systems. The fyke nets are suspended by placing floats at the apex of each hoop, and on the top of the opening frames. This is done to prevent the nets from sinking into the soft sediments at the bottom of the bogs. CRAYFISH AND MINNOW TRAPS There have been introductions of exotic crayfish species in recent years into many north temperate lakes. Monitoring yearly abundances of crayfish species is important in determining the status and extent of the invasions. 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. Starting in 1998, three traps are set per site. Thus, prior to 1998, thirty traps were set on each lake (covering 6 sites.) As of 1998, 18 traps are set on each lake. 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 per trap to attract minnows inhabiting the bogs. Crayfish traps are baited with 120 g of liver. Traps are fished for approximately 24 hours . Crayfish are identified to species and returned to the lake. Minnows caught in either the crayfish or minnow traps are identified to species, measured for total length. Minnow traps used 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. GILL NETS In most lakes, there are species of fish which inhabit the pelagic (open water) zone. These fish species can have a large impact on lake ecosystem dynamics when they occur in abundance. To monitor yearly changes in the abundance of pelagic fish species, we sample the deep basin of eight of the LTER lakes with vertical gill nets. Our gill nets are a set of 7 nets, each in a different mesh size, hung vertically from foam rollers, 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. One side of the net is marked in meters from top to bottom. Stretcher bars have been installed at 5 meter intervals from the bottom to keep the net as rectangular as possible when deployed. The bottom end is weighted with a lead pipe to quicken the placement of the net and to maintain the position of the net on the bottom. 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 nets are set in a straight line, each connected to the next, and anchored at each end of the line. Once the nets are in position, they are unrolled until the bottom end reaches the bottom, and then tied off to prevent further unrolling. The nets are pulled by placing each net onto a pair of brackets attached to the side of the boat and rolling the net back onto its float; the fish are picked out as the net is brought up, placed in tubs according to depth. The fish are processed when the net is completely rolled up and before it is redeployed. ELECTROFISHING We use a boom style electrofishing system 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. Two crew members in the bow of the boat dip up all stunned fish, placing them in the live well for processing at the end of each transect. Transect lengths vary depending upon the size of the lake. If the end of a transect is reached before 30 minutes has elpased, time is paused while the electrofisher loops back to the start of the transect. The transect is then repeated for the remaining time. In 1999, dip nets were standardized to 10 foot poles attached to 18in. x 20in. tear drop shaped hoops. The nets are made of 7 mm stretch mesh. PROCESSING THE CATCH For all collecting methods, the fish are processed as follows. Each individual fish is identified to species. If it cannot be positively identified, after it is processed, it is preserved in 10percent buffered formalin or 95percent ethanol for later identification. The total length of the fish (measured from nose to end of caudal fins pinched together) is measured in mm. Prior to 1997, the weight (g) of the first 5 fish of each species in each 10 mm size category was also measured, using the appropriate Pesola spring balance (fish weight registering in the middle range of scale). A tally sheet was used to record how many fish in each size category had been measured. Starting in 1997, 2 fish are weighed for each fish species in each 5mm size category. Also in 1997, data recording switched to an electronic system which tallied measured fish. For yellow perch, rock bass, and cisco, a scale sample is collected from each weighed fish. This is removed from the left side of the fish, above the lateral line and below the origin of the dorsal fin. Scale samples are stored in scale envelopes and labeled with a unique ID number, the date the scale was taken, a lake ID number, the species code, land length and weight. For gill net catches, the depth at which each individual is caught is also recorded. Fish from all gear (except gillnets) are held in live wells during processing. Fish are sorted by species into buckets, processed as quickly as possible, and returned to the lake. Fish from the gillnets are very rarely alive. If alive, they are usually badly damaged when the nets are raised. PROTOCOL CHANGES 1983 Discontinued fykenets 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 full suite of sampling gearr 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</p>
Publication Date
Short Name
NTLFI03
Version Number
32

Lake Wingra: Fish Lengths and Weights

Abstract
Data are collected annually to enable us to track the fish assemblages of Lake Wingra. Sampling is done at six littoral zone sites per lake with a beach seine, minnow or crayfish traps, and fyke nets, while a boat-mounted electrofishing system samples four littoral transects. Vertically hung gill nets are used to obtain two pelagic samples per lake from the deepest point. A trammel net samples across the thermocline at two nearshore sites per lake. Fish are identified to species. Lengths are measured for all fish caught, while weight and scale are collected from a subset. Derived data include catch per unit effort and size distribution by species, lake, and year. Sampling Frequency: annually Number of sites: 1. Note that 2020 data does not exist due to insufficient sampling.
Core Areas
Dataset ID
181
Date Range
-
LTER Keywords
Maintenance
ongoing
Metadata Provider
Short Name
FOLWFI01
Version Number
19

North Temperate Lakes LTER: Phytoplankton - Trout Lake Area 1984 - current

Abstract
Phytoplankton samples from the seven LTER lakes in the Trout Lake area (Allequash, Big Muskellunge, Crystal, Sparkling, and Trout lakes and bog lakes 27-02 [Crystal Bog], and 12-15 [Trout Bog]) are collected six times per year at the deep hole sampling station at the same time our other limnological sampling is conducted. Sampling dates include winter under ice, spring mixis, June, July, August, and fall mixis. Phytoplankton samples are made into permanent slide mounts, 3 slides per sample, and are archived at the University of Wisconsin - Madison Zoology Museum. Slides are available for all years, however species identification and counts have not been done for all available slides. Sampling Frequency: 6 samples per year. Number of sites: 7
Dataset ID
238
Date Range
-
LTER Keywords
Maintenance
ongoing
Metadata Provider
Methods
Phytoplankton samples are collected using a peristaltic pump and tubing, collecting a separate sample from the epilimnion, metalimnion and hypolimnion for most of the lakes. For 27-2 Bog Lake, which is only 2m deep, we collect one 0-2m composite sample. The samples are preserved with Lugol's iodine solution. We create a single hypsometrically pooled composite sample per lake from subsamples of the epi, meta, and hypo samples. The pooled samples are sent to PhycoTech, Inc., a private lab specializing in plankton analysis, to be made into permanent slide mounts. The slides are archived, and no wet samples are saved.
Short Name
NTLPL08
Version Number
19

Cross Lake Comparison at North Temperate Lakes LTER - Zooplankton Biomass Study 2006

Abstract
This project investigates why zooplankton size, but not biomass, has been found to influence the phosphorus (TP) - chlorophyll a (chl a) relationship (Pace 1984, Carpenter et al. 1991, Carpenter et al. 2001).
Dataset ID
220
Date Range
-
LTER Keywords
Maintenance
completed
Metadata Provider
Methods
Total phosphorus, chlorophyll a, and zooplankton samples were collected from 19 lakes in northeastern Wisconsin and Upper Michigan. Thirteen lakes are in Vilas County, WI (Star Lake, Anvil Lake, Stormy Lake, Camp Lake, Crab Lake, Little Crawling Stone Lake, Sparkling Lake, Lake Laura, Big Portage Lake, Crystal Lake, Tuesday Lake, Trout Lake, Lac du Lune, and Lynx Lake), one lake is in Oneida County, WI (Indian Lake) and 5 lakes lie within the University of Notre Dame Environmental Research Center (Peter Lake, Paul Lake, Tuesday Lake, Crampton Lake and Long Lake). The lakes were sampled in late May and June 2006. All sampled lakes lie within the coordinates 45 36 to 46 18 N and 89 00 to 89 54 W. Samples were collected from the deepest part of each lake. Lake information: Data collected on the sampledate include air temperature, an estimate of cloud cover, an estimate of wave height, maximum depth, secchi depth, and the depths of the epilimnion, metalimnion, and hypolimnion. Lakes identified as being located in UNDERC lie within the University of Notre Dame Environmental Research Center near Land O Lakes, Wisconsin, USA (89 32 W, 46 13 N). The location of the remaining lakes is identified by county - either Vilas or Oneida. Zooplankton Biomass: Five replicate zooplankton samples were collected from the deepest spot of each lake using vertical tows with a Wisconsin net (80 um mesh, 0.11 m radius). The tow was from 2 meters above the bottom of the lake to the surface. Zooplankton samples were preserved in 70percent ethanol. Each sample was drained through an 80 um mesh and sub-sampled three times using a 1 mL Hensen Stempel Pipette, and all zooplankton present in each subsample were identified down to genus or species. Thirty zooplankton of each genus or species in each 1 mL rep were measured using an ocular micrometer and a Leica MZ-8 dissecting microscope. To calculate biomass, the average weight for each species or genus per sample was applied to published dry weight- length regressions. Length-weight regressions (see methods) used to calculate biomass Zooplankton Lengths: Thirty zooplankton of each genus or species were measured using an ocular micrometer in a Leica MZ-8 dissecting microscope. All measurements are in mm. Note: Length measurements for Holopedium gibberum are of the post abdominal claw (between the setae natatores and the terminal claw). Total body length can be determined from the equation: Post abdominal claw length (um) equals 191.64 times Total Length (mm) plus 37.0 (Yan and Mackie 1986) Water Temperature/Dissolved Oxygen Profiles: A temperature and dissolved oxygen profile was taken on each lake on the sampling date Total Phosphorus and Total Nitrogen: Six samples were collected to determine the total phosphorus of each sampled lake. Triplicate 100-mL integrated samples were collected with a plastic tube (1.9 cm diameter) from the epilimnion. Discrete total phosphorus samples were collected with plastic tubing (0.6 cm) and a peristaltic pump from the middle of the metalimnion, the top of the hypolimnion and 1 meter above the bottom of the hypolimnion. Samples were preserved with 1 mL of Optima HCl and analyzed spectophotometrically for total phosphorus and total nitrogen. Some of the lakes were not completely stratified at the sampledate slightly altering the sampling method. In Crab Lake, Stormy Lake and Trout Lake the thermal profile made it difficult to determine the division between meta- and hypolimnion, so two additional samples were collected - from the metalimnion and from the top of the hypolimnion. In Anvil Lake, Big Portage Lake, Camp Lake, and Indian Lake, only one hypolimnion sample was collected because the lakes are shallow and were not completely stratified. Chlorophyll-a: Six integrated chlorophyll a samples (three epi- and three metalimnion) were collected from each lake using a plastic tube (1.9 cm diameter) and analyzed flourometrically. Sampling Frequency: Each of 19 lakes sampled once Number of sites: 19
Short Name
ZPBMASS
Version Number
22
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