Dataset: Mussel bed phototransects

Photos were taken between 2011-07-27 and 2015-06-19.  Mussel beds imaged were between approximately 1.5m and 4.5m above mean lower low water (MLLW) in areas of moderate to heavy wave exposure. Permanent transects were established at 8 sites using stainless steel bolts and washers affixed to the rock. Ends of each transect were of the same tidal height. Transects were spaced 2m apart in the xy plane.

For photography, transect lines were placed between bolts at each of three tide heights. Plastic livestock tags were placed, at minimum, at 1m intervals along the transect. Additional tags were placed midway between each tag on the line (estimated by eye), and above and below the transect lines at similar intervals. Additional tags were placed as needed to ensure that tags appeared in each photograph and to mark features of interest such as hummocks.

Photos were taken with a Nikon DSLR D300(B), with an AF-S Nikkor 18-55mm lens. Lens was set at 18mm for all photos. The camera was mounted on a survey pole with a camera armature mounted on top. The armature extends 1m horizontally from the pole. The survey pole was extended vertically to 2.25m for the photos and a remote used to trigger each photo. The survey pole spirit level was used to ensure the camera was as parallel to the xy plane as possible. For each photo, the camera was centered over each tag placed at 1m intervals on the transect line and at the tags placed midway between each transect. A laser pointer attached to the camera helped center each photo. Additional photos were taken as needed to ensure complete coverage of the area, particularly above and below the uppermost and lowermost transect lines.

Zip files containing the phototransects for each site are available on the data page and can be found by pressing the "Get Data" button.