Dataset: Site List

At each site, we sampled two rocky intertidal areas (usually one on either side of a beach or headland and separated by approximately 100 meters) during low tide (usually less than -0.8 feet), using quadrats to estimate abundances of Pisaster ochraceus, Cryptochiton stelleri, Leptasterias sp., and Henricia pumila. We exhaustively searched 20–32 one-meter square quadrats per site (i.e. 10–16 per each of 2 areas), recording GPS waypoint, time, and abundances and sizes of the target species for each quadrat. Each quadrat was photographed. Quadrat locations were selected by first finding one of the target habitat types—surf grass, low-zone red algae, coralline turf, cobble or boulder field, or urchin pools with pits either empty or occupied—selecting a starting point haphazardly, and then using a random numbers table (range of 1–10 meters) to choose remaining quadrat locations. All quadrats and specimens were georeferenced using a Garmin C60X GPS (±3 m precision). The accuracy of the GPS in meters at the time the waypoint was recorded can be found in column "GPS_Accuracy" of the "Quadrat data" dataset. Tissues samples are preserved in 95% Ethanol and stored at -20 degrees C. A subset of tissue samples are also preserved in RNA Later and stored at -20 degrees C (as indicated in the "Quadrat data" dataset).  

 

Problem report for data between 2018-12-21 and 2019-07-06: In Strongylocentrotus purpuratus were only counted in the first quadrant (0.25 x 0.25m) of each quadrat (1m2), so the total search area for that species is one quarter that of other species and so the density should be calculated accordingly.