Pilot Program Methodology for 2005 

Long-term monitoring for invasive species involves recording the presence of native species as well as the bioinvaders over time. With both sets of information, it may be possible to understand the impact bioinvaders are having on native species.

Intertidal communities are highly variable since they are subject to many diverse natural conditions and disturbances, as well as human impacts. Therefore, a successful monitoring program must conduct repeated sampling of specific parameters at established locations over long enough time periods to take into account the natural variability of the biological communities being observed (Murray et al. 2002).

A random quadrat method is employed in the cobble habitat or rocky intertidal zone to determine the densities of native and invasive crabs. Each quadrat is a one or two square meter square outline composed of PVC piping. Each team will have a separate data sheet for each quadrat on which to record the species, sex, and size of the crabs.

Sampling Data Sheet
*Random Number Generator

*Note: To get different sets of numbers, you just have to press Control and ‘r’ at the same time. If it gives you an error about ‘macros’, please go to ‘Tools’ then ‘Options’ and lastly to the tab to macros, and low the security level, it is fine. This will create tables of randomly generated values, please print out a few copies of different random number and bring them to the sampling site.


Monitoring Intertidal Rocky Shoreline: Random Quadrats Method

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


Ziplock bags or watertight container

70% - 95% ethanol from CVS or a pharmacy

Camera and /or compasses   

Net for capturing mobile organisms

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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