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Abalone and Sea Star Monitoring
Band
Transect/Irregular Plot Protocol
The number and size of seastars (primarily ochre seastars Pisaster ochraceus) and black abalone (Haliotis cracherodii) are monitored along band transects or within irregularly-shaped plots, depending on site topography. Seastar transects are typically 2 x 5 m; abalone transects are typically 1 x 10 m. Transects are marked at both ends (and often in the center) by notched bolts. Irregular plots are marked by four "corner" bolts. All black abalone and ochre seastars in transects or irregular plots are counted and measured (abalone: shell length; seastars: from center to tip of longest ray).
Timed Searches Site-wide timed searches have been employed at locations where abalone and seastars exist in too few numbers to monitor within a limited area. One person spends 30 min (or 2 persons 15 min each) searching crevices and pools along the low intertidal zone haphazardly throughout the site for possible occurrences of ochre seastars or black abalone. Numbers encountered and size measurements (at some sites) are recorded.
Owl Limpet Counts and Size Frequencies The number and size distribution of owl limpets (Lottia gigantea) are monitored each spring and fall to follow population dynamics within 5 permanent circular plots per site at most intertidal sites with sufficient scorable individuals (generally > 20 individuals/plot). Plots were established in areas of high density to obtain as many measurements as possible, preferably > 100 per site. Plots are marked with a center bolt, notched to indicate the plot number. Limpets are measured within a circle (typically 1 m radius, 3.14 m2 area) around each bolt. A 1m length of line or tape is attached to the bolt and arced around to form the circle. Owl limpets found within that circle (including those touched by the 1 m mark) are measured with calipers to the nearest millimeter, then marked with a crayon to avoid scoring duplication. Limpets are never removed from the rock.
Photoplots The cover of target
species as well as other core and optional species/taxa/substrates is
sampled by photographing 5 (at most sites) permanent 50 x 75 cm plots per
target species, then scoring point contact occurrences on the photo image. Plots were established in areas of high target species density wherever
possible. Photoplots typically are scored
from the photographs in the laboratory, supplemented when possible by field
plot sketches and notes. For film photographs, each slide is projected onto
a grid of one hundred evenly-spaced points (10 x 10). Individual taxa
beneath the points are identified and recorded. When scoring digital images,
a grid is created on
an LCD computer monitor (using Adobe Photoshop)
of one hundred ev
Transects The cover of surfgrass (Phyllospadix spp) is sampled by point-intercepts along 10 m long permanent transects. Transects were established in areas of high surfgrass density wherever possible. Most sites have 3 replicate transects. Transects may run end to end or be separated widely, depending on the shape and expanse of the surfgrass bed. Each transect is divided into 100 points distributed at 10 cm intervals. The top-layer target, core, or optional species/taxon/substrate is scored under each point. In addition, surfgrass is separately scored if it occurs beneath another species. In the latter situation, total transect cover can be greater than 100%.
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Updated: 12/9/2004 |
