Monitoring Intertidal Rocky Shoreline: Random Quadrats Method
Overview
The targeted invasive species for the rocky intertidal habitat are Hemigrapsussanguineus (Asian shore crab) and Carcinus maenas (European green crab). Therefore, shorelines are selected that consist of cobble substrate in the mid to low tidal zones where these crabs are normally expected to seek shelter at low tide. This monitoring must be conducted around low tide.
A targeted evaluation area is established, divided into four sections, and then a square meter quadrat (an open square made out of PVC piping) is randomly placed in each of the four sections. It is important to understand that the evaluation area is consciously selected, allowing for repeatability, but the quadrat sampling is random, which eliminates bias and intentional targeting of a species or microhabitat. If the location of the sampling quadrat was chosen in a nonrandom manner, an unrealistic assessment of the evaluation area would result.
The goal of long-term monitoring is to return to the same evaluation site at regular intervals. Long term monitoring has a higher power to detect changes in intertidal species if the same location is returned to over time (Murray et al. 2002). When data are repeatedly collected from a site over an extended time period, an average abundance can be derived, and trends may be extrapolated. Once a month sampling from spring through fall is a good target but (one or) two times a year will suffice for participation in this pilot program. Monitoring once during the winter months would be a bonus, but weather conditions do not always permit this. Monitoring teams can consist of as few as two to as many people as you have.The safety of the data collectors is always of paramount importance, and no one should ever put themselves in danger to collect data.
Equipment Needed: |
Two 30 meter tapes or two ropes with meter markings |
One or two meter2 quadrat made from PVC pipe (I will provide these for the day of sampling with me) |
Clipboards and pencils (not pens) |
Data sheets (provided on the website) |
Marine Invasive ID Cards or Marine Field Guides |
Thermometer |
Ziplock bags or watertight container |
70% - 95% ethanol from CVS or a pharmacy |
Camera and /or compasses |
Net for capturing mobile organisms |
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Figure from:
E.F. Ricketts and J. Calvin 1968 Between Pacific Tides, fourth edition revised by J.W. Hedgpeth, Stanford University Press.
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