US Long-Term Ecological Research Network

Excerpt from:

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.

Sampling Sites
This method employs a point-intercept design in which a grid of sampling sites is distributed evenly over the entire lake surface (Figure I). Lake organizations or individuals can request an electronic file of survey sites by contacting the WDNR Lake Coordinator from their region with the lake name and county, as well as the town, range and section (TRS) or water body identification code (WBIC). Please make requests well in advance of planned field work to allow WDNR staff sufficient time for map creation (recommend at least I month). WDNR staff will determine the number of sites and grid resolution based on the estimated size of the littoral zone (the area in which plants grow) and shape of the lake. Grids will be scaled to produce a greater number of sites on lakes that are larger and have more  complex shorelines. Lakes with a narrow littoral zone may be assigned a comparatively high number of sampling sites to achieve sufficient survey coverage. Once created, the sampling map and an associated GPS text file containing the latitude and longitude information associated with each sample site is provided electronically by the WDNR.

Necessary equipment:
• Appropriate watercraft and all equipment required by state law
• Double-sided sampling rake attached to a 15-ft (4.6m) pole
• Weighted sampling rake attached to a 40-ft (12m) rope
• Handheld GPS receiver with WDNR sample sites loaded
• Print-out of lake map with WDNR sample sites
• Print-out ofWDNR field datasheets on waterproof paper
• Pencils
• Sea lable storage bags for voucher specimens
• Waterproof voucher sample labels
• Cooler(s) with ice for storing voucher specimens
• Depth finder

The rake samplers are each constructed of two rake heads welded together, bar-to-bar, to form a double-sided rake head. The rake head is 13.8 inc hes (35 centimeters) long, with approximately 14 tines on each side. For use in shallow waters, mount a double-sided rake head to a pole that has the capability to extend to 15 feet (4.6 meters). For use in deep er waters, attach a second double-sided rake head to a rope; this rake head should also be weighted.

Using the Rake Samplers Collect one rake sample per sample site. In water shallower than IS feet deep, use the pole sampler. At each sample site, lower the rake straight through the water column to rest lightly on the bottom, twist the rake around twice, and then pull the rake straight out of the water. In water deeper than IS feet, drop the rope sampler straight into the water alongside the boat, drag the rake along the sediment sur face for approximately one foot (0.3 rn), and then pull the rake to the surface. A large tray or bin may be used to aid in processing the entire sample.

Rake fullness
At each site, after pulling the rake from the water record the overall rake fullness rating that best estimates the total coverage of plants on the rake (I - few, 2 - moderate, 3 abundant). Also identify the different species present on the rake and record a separate rake fullness rating for each. Account for plant parts that dangle or trail from the rake tines as if they were fully wrapped around the rake head. The rake may dislodge plants that will float to the surface, especially short rosette species not easily caught in the tines. Include the rake fullness rating for plants dislodged and floating but not collected on the rake. Record rake fullness ratings for filamentous algae, aquatic moss, freshwater sponges, and liverworts, but do not include these ratings when determining the overall rake fullness rating. While at a site, perform a brief visual scan. If you observe any species within 6 feet (2m) of the sample site, but not collected with the rake, record these species as observed visually ("V") on the field sheet. These species will be included in total number of species observed.

Inaccessible sites
It may be imposs ible or unsafe to reac h some sample sites. Where the water is very
shallow, rocks are present, or dense plant growth prevents navigation, fie ld workers
should attempt to access the site as long as do ing so is safe and relative ly practical. It is
often possible to reach difficult sites by using oars or poling; howe ver, keep safety in
mind and practice good judgment. Do not get out and drag the boat thro ugh mucky
sed iment to reach a site. If the sampling site is shallow but the substrate is firm, yo u may
be able to walk to the site from shore or from the boat. If you cannot access a s ite, leave
the depth blank and record the appropriate comment on the field datasheet from the list
below. Remember to also transfer these to the "Comments" column of the ENTRY sheet
(see data entry section) :
1. Sample site cannot be accessed due to thick plant growth.
2. Aquatic plants that are visible within 6 feet of a non-navigable sample site (e.g. water
lilies, cattails, bulrushes, etc.) should be recorded as visuals (V) on the datasheet.
1. Sample site occurs on land (including islands).
2. Aquatic plants visible within 6 feet of a terrestrial sample site (e.g. water lilies, cattails,
bulrushes, etc.) may be included in the general boat survey list, but should not be marked
as visuals (V) on the datasheet.
3. Only species rooted in water should be recorded as present or as part of the boat survey.
1. Sample site is in water that is too shallow to allow access.
2. Aquatic plants that are visible within 6 feet of a shallow sample site should be recorded as
visuals (V) on the datasheet.
1. Sample site is inaccessible due to the presence of rocks.
I. Sample site is inaccessible due to the presence of a dock or pier.
I. Sample site is inaccessible due to the presence of a designated swimming area.
I. Sample site is inaccessible due to the presence of a temporary obstacle such as a boater,
swimmer, raft, loon, etc.
2. If possible, try to revisit this site later on during the survey once the temporary obstacle has
I. No information is available about the sample site because it was not traveled to
(inaccessible channel, accidently omitted during survey, skipped due to time constraints,
I. Site was not sampled for another reason; please provide a brief description.