Methods

Sampling methods are described by Szydlowski et al. "Macrophyte and snail community responses to 30 years of population declines of invasive rusty crayfish (Faxonius rusticus)," but are provided here for convenience. Instrumentation is further documented in the supplementary information of the paper.<br/>Sampling methods are described by Szydlowski et al. "Macrophyte and snail community responses to 30 years of population declines of invasive rusty crayfish (Faxonius rusticus)," but are provided here for convenience. Instrumentation is further documented in the supplementary information of the paper.<br/>Sampling methods are described by Szydlowski et al. "Macrophyte and snail community responses to 30 years of population declines of invasive rusty crayfish (Faxonius rusticus)," but are provided here for convenience. Instrumentation is further documented in the supplementary information of the paper.<br/>Sampling methods are described by Szydlowski et al. "Macrophyte and snail community responses to 30 years of population declines of invasive rusty crayfish (Faxonius rusticus)," but are provided here for convenience. Instrumentation is further documented in the supplementary information of the paper.<br/>Sampling methods are described by Szydlowski et al. "Macrophyte and snail community responses to 30 years of population declines of invasive rusty crayfish (Faxonius rusticus)," but are provided here for convenience. Instrumentation is further documented in the supplementary information of the paper.<br/>Sampling methods are described by Szydlowski et al. "Macrophyte and snail community responses to 30 years of population declines of invasive rusty crayfish (Faxonius rusticus)," but are provided here for convenience. Instrumentation is further documented in the supplementary information of the paper.<br/>Sampling methods are described by Szydlowski et al. "Macrophyte and snail community responses to 30 years of population declines of invasive rusty crayfish (Faxonius rusticus)," but are provided here for convenience. Instrumentation is further documented in the supplementary information of the paper.<br/>Sampling methods are described by Szydlowski et al. "Macrophyte and snail community responses to 30 years of population declines of invasive rusty crayfish (Faxonius rusticus)," but are provided here for convenience. Instrumentation is further documented in the supplementary information of the paper.<br/>Sampling methods are described by Szydlowski et al. "Macrophyte and snail community responses to 30 years of population declines of invasive rusty crayfish (Faxonius rusticus)," but are provided here for convenience. Instrumentation is further documented in the supplementary information of the paper.<br/>

Methods

the protocol employed here is based on:
Hauxwell, J., S. Knight, K. Wagner, A. Mikulyuk, M. Nault, M. Porzky and S. Chase . 2010. Recommended baseline monitoring of aquat ic plants in Wisconsin : sampling design, field and laboratory procedures, data entry and analys is, and applica tions. Wisconsin Department of Natural Resources Bureau of Science Services, PUB-SS-1068 2010. Madison, Wisconsin, USA.

Methods

Macrophyte cover in Sparkling Lake was assessed in the third or fourth week of July from 2002-2004 and from 2007-2010. Eight transects were selected to correspond to trap survey sites for rusty crayfish and represent the range of macrophyte communities in the lake. These transects stretched from the waterline to a depth of 4 meters, running perpendicular to shore. Circular quadrats (1m2) were placed along each transect at 1 m longitudinal intervals, and observers using SCUBA estimated visually the percent cover of each macrophyte species within the quadrat. The sum of percent cover of all species within a quadrat does not necessarily add to 100; rather, this sum reflects the percentage of bottom substrate covered by macrophytes.

Methods

To control for sampling methodology and allow comparisons among native and invasive species, we only included data where both invasive and native species from a taxonomic group were sampled using the same methods across multiple sites. Exceptions were made to include rusty crayfish (Orconectes rusticus) in its native range and zebra mussel (Dreissena polymorpha) data. Native rusty crayfish data were obtained from (Jezerinac 1982). Zebra mussel data were mainly obtained from a meta-analysis (Naddafi et al. 2011) which compiled data from 55 European and 13 North American sites from 1959-2004. Additional densities from North America were compiled from multiple primary literature sources (Table S3). All zebra mussel records were presented as number per m2 and are from their invaded range; we did not include native mussel data.Crayfish data were obtained from multiple sources. Crayfish were collected in Wisconsin, USA during summers of 2002-2010 from lakes in the Northern Highlands Lake District following their protocol for crayfish collection. Crayfish were sampled in Wisconsin streams tributary to Lake Michigan from 2007-2010 using 10 gee-style minnow traps per site baited with chicken livers and set overnight. Swedish crayfish were sampled using 30 minnow traps baited with frozen fish in lakes and streams of southern Sweden from 2001-2003 as described in (Nystrom et al. 2006). Washington crayfish were collected from 100 lakes in the Puget Sound Lowlands region of Washington State, USA between 2007 and 2009 from mid-June to early October of each year. At each lake, the investigators set 20 minnow traps baited with fish-based dog food. Traps were deployed in four clusters of five traps each and recovered the following day. All crayfish densities are presented as number per trap per day, with the exception of native range rusty crayfish data, which were reported as number per site (Jezerinac 1982) and excluded from all comparisons that depend on sampling units.Wisconsin fish data were collected from streams throughout the state from 2005-2010 using either a backpack or towboat electrofisher with pulsed DC current in wadeable (less than1m depth) streams for a minimum of 15 minutes. For Wisconsin trout species, locations sampled within 10 years following a stocking event of that species were excluded. Lamprey data were collected from 2008-2010 from Great Lakes tributaries using backpack electrofishers following standardized methods as a part of the sea lamprey assessment program of the United States Fish and Wildlife Service and Department of Fisheries and Oceans, Canada. North American fish densities are presented as number per minute of sampling. Swedish fish data were collected using backpack electrofishing between 1980 and 2010 from streams in Vasterbotten county, northern Sweden, and were obtained from the Swedish Electrofishing REgister (SERS), www.fiskeriverket.se, and are reported as number per 100 m of stream.Snail data were collected in 2006 from lakes in the Northern Highlands Lake District in Wisconsin as described by (Solomon et al. 2010), and densities are presented as number per two m2. Aquatic plant data were collected using a systematic grid-based point-intercept sampling methodology to record macrophyte frequency of occurrence in 242 Wisconsin lakes from 2005-2008. Aquatic plant presence absence was recorded from a boat using a double-sided rake sampler at each point on a sampling grid as described in (Mikulyuk et al. 2010). Density data are presented as proportion of sites within lake littoral zone where a species was present.For all data, if multiple records existed from the same location, we used the most recent record. If replicate samples existed within the same site on the same sampling date, the mean value was used.

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. The site descriptions specify a transect line along which presence or absence data is recorded for all macrophyte species. A 0.25 M2 ring placed at 1 meter intervals (except site 7 - 0.5 to 1 M depth where the ring is placed at 2 meter intervals) along the transect designates the sampling quadrat. Using SCUBA, species data are recorded along with the total number of quadrats encountered between the following depth intervals: 0.5-1 M, 1-2 M, 2-3 M and 3-5 M. These depth intervals have been permanently established with markers consisting of a commercial Earth Anchor set in the lake bottom with 2 floats secured to it near the bottom. Large boat bumpers are used on the anchors at 3 and 5 meters. Between 28 and 52 quadrats are examined within each depth interval at each site.
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.

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. The site descriptions specify a transect line along which presence or absence data is recorded for all macrophyte species. A 0.25 M2 ring placed at 1 meter intervals (except site 7 - 0.5 to 1 M depth where the ring is placed at 2 meter intervals) along the transect designates the sampling quadrat. Using SCUBA, species data are recorded along with the total number of quadrats encountered between the following depth intervals: 0.5-1 M, 1-2 M, 2-3 M and 3-5 M. These depth intervals have been permanently established with markers consisting of a commercial Earth Anchor set in the lake bottom with 2 floats secured to it near the bottom. Large boat bumpers are used on the anchors at 3 and 5 meters. Between 28 and 52 quadrats are examined within each depth interval at each site.
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.

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. The site descriptions specify a transect line along which presence or absence data is recorded for all macrophyte species. A 0.25 M2 ring placed at 1 meter intervals (except site 7 - 0.5 to 1 M depth where the ring is placed at 2 meter intervals) along the transect designates the sampling quadrat. Using SCUBA, species data are recorded along with the total number of quadrats encountered between the following depth intervals: 0.5-1 M, 1-2 M, 2-3 M and 3-5 M. These depth intervals have been permanently established with markers consisting of a commercial Earth Anchor set in the lake bottom with 2 floats secured to it near the bottom. Large boat bumpers are used on the anchors at 3 and 5 meters. Between 28 and 52 quadrats are examined within each depth interval at each site.
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.

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.

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.

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. For each rake cast, filamentous algae and any aquatic macrophyte species present are assigned a density rating from 0-5 based on the extent of coverage of the upper rake head. Determination of extent of coverage involves judgment of the surveyor as to the number of rake teeth and area of teeth covered by each species. It is necessary to separate plants to assess individual species coverage. Ratings from the 4 rake casts at each station can be averaged to compute an overall density rating for each species found 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. Before removing the plant material from the rake, drape the long strands over the rake and gently push the plant material down on the rake. Assign a rake rating (from 1 to 5) depending on how much the plant material covers the rake prongs. The rake prongs are painted in 20 percent increments. If the plant material only covers the lowest 20 percent of the rake prongs, assign the rake rating a 1. If the plant material covers between 20 percent and 40 percent of the rake prongs, the rake rating is a 2, and so on. 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. Separate the filamentous algae from the rest of the plant material. Separate and identify the individual plant species, throwing out any dead plant material. Give the filamentous algae and each plant species a rake rating (note that it is often necessary to visualize how much space each species would take up on the rake prongs rather than actually placing each species onto the rake). If a plant species can not be identified, take a sample back to the lab by putting it in a ziplock bag with a small amount of water and temporarily storing it in a cooler. Repeat the above steps until 4 rake tosses have been thrown. Normally 2 rake tosses are thrown out each side of the boat to an area where the water depth is known to be at the desired depth. Move to the next half-meter depth. Macrophytes are collected at each half-meter water depth from 1 meter to 4 meters.