The intent of the subtidal monitoring program is to characterize the structure and dynamics of a kelp forest community. For this reason surveys are designed to sample a large number of ecologically and economically important species throughout the entire area of a kelp forest. In addition, we quantitatively characterize reef attributes (depth, substratum type, relief) that may explain spatial patterns of variation among samples.
We define a site as a contiguous rocky-reef habitat along a portion of the coast greater than 500 m in length. Within that section of coast, surveys are conducted across a depth range from 5 m to 20 m, or to the deepest extent of the reef if it is less than 20 m deep. Most of the areas we monitor support forests of giant kelp, Macrocystis pyrifera, or bull kelp, Nereocystis leutkeana.
We divide each site into two survey areas located approximately 500 meters apart within the same reef complex. Within each area, sampling is stratified across zones defined either by depth (shallow to deep) or proximity to shore (onshore to offshore edges of the reef). The basic unit of sampling is a transect. Our survey design is based on analytical models that allow us to describe the direction and magnitude of change in kelp forests over time. To achieve this, we sample randomly located transects within each of the stratified zones in each area.
Fish and algae/invertebrate surveys are conducted separately at each site due to time limitations imposed by the procedure used to sample the algae and invertebrates. Four sampling methods are employed to measure different species groups. Details of the survey designs and the methodologies are given below.
For further information see the recent description of the PISCO subtidal monitoring program provided to the Cooperative Research and Assessment of Nearshore Ecosystems (CRANE) program: crane_protocol.pdf
Fish Survey Design
Fish Sampling Methodology
Algae and Invertebrates Survey Design
Uniform Point Contact Methodology
PISCO Subtidal Survey Training
Algae and Invertebrate Training
At each monitoring site, visual surveys by scuba divers are used to quantify the size structure and density of fish populations and the species composition and structure (i.e., relative abundance) of fish assemblages.
To assure that the 3-dimensional habitat created by kelp forests is sampled thoroughly, fish transects are stratified across the face of the reef (alongshore and cross-shore) and vertically through the water column. In each of the two areas that constitute a site, three transects are sampled in each of four zones (see fish sampling schematic above-right and map-view diagram below-right). The zones are stratified to encompass the offshore edge of the reef, the middle of the reef, and as shallow inshore as practical. For example, for a maximum depth of 20 meters (m) the depth zones would be 5, 10, 15, and 20 m. If no appreciable depth stratification is present, then the stratification is based on proximity to the outer edge of the reef and the shore. In each zone, three randomly located transects are sampled along isobaths (constant depth) parallel to shore.
In cases where a reef does not extend very far offshore (e.g. narrow, steep reefs found in the Channel Islands), it may be unsuitable to sample four depth or distance strata. In this case, a modified sampling procedure is done based on three areas and two depth zones. In this case, 4 randomly located transects are sampled in each of two depth zones in three areas resulting in 24 transects.
Three portions of the water column (bottom, midwater and canopy) are sampled by two divers along each transect (see figure to the right). Bottom transects sample the bottom 2 m of the water column, contiguous with the reef surface, and the midwater transect is located just above and slightly offshore and forward of the bottom transect. The height of the midwater transect varies as a function of bottom depth (4-6 m above the bottom for bottom depths of 10 m or greater, 2-4 m above the bottom for bottom depths of 6 m or less). Bottom and midwater transects are sampled simultaneously by two divers. After completion of bottom and midwater transects, divers move up to the canopy and moving in the opposite direction, count fish in the top 2 m of the water column (0-2 m depth) only. One diver samples the fish while the other diver estimates percent canopy cover along the 30 m long transect.
Both divers in the team identify, count and size all conspicuous fishes on each 30 m long x 2 m tall x 2 m wide transect. If gender is visually distinguishable (e.g., kelp greenling or California sheephead), this is recorded as well. Divers estimate total length (TL) of small fish (< 20 cm TL) to the nearest cm, and larger fish (> 20 cm) to the nearest 5 cm interval, as they reel out a 30 m tape.
Fish surveys take place from approximately mid-August through October. Four divers can sample 24 transects (combined bottom, midwater and canopy) at one site within one day.
Canopy surveys are timed to capture net annual recruitment of reef fish that settle to the kelp canopy. As a result, in central California, canopy surveys are conducted separately and later in the season than bottom-midwater surveys. In Southern California, canopy surveys are conducted simultaneously with bottom-midwater surveys. When conducted separately, canopy surveys (24 transects per site) are stratified across the reef identical to that of bottom transects, sampling the top 2 m of the water column (0-2 m depth) only.
At each monitoring site, visual surveys by scuba divers are used to quantify the size structure and density of macroalgae and invertebrate populations and the species composition and structure (i.e., relative abundance) of their assemblages.
To assure that the entire kelp forest is sampled representatively, benthic transects are stratified across the face of the reef (alongshore and cross-shore). In each of the two areas that constitute a site, two transects are sampled in each of three zones (see Algae and Invertebrate Sampling Design schematic above and map-view diagram below). The zones are stratified to encompass the offshore edge of the reef, the middle of the reef, and as shallow inshore as practical. For example, for a maximum depth of 20 meters (m) the depth zones would be 5, 12.5, and 20 m. If no appreciable depth stratification is present, then the stratification is based on proximity to the outer edge of the reef and the shore. In each zone, two randomly located transects are sampled along isobaths (constant depth) parallel to shore.
In cases where a reef does not extend very far offshore (e.g. narrow, steep reefs found in the Channel Islands), it may be unsuitable to sample three depth or distance strata. In this case, a modified sampling procedure is done based on three areas and two depth zones. In this case, 2 randomly located transects are sampled in each of two depth zones in three areas resulting in 12 transects.
Three sampling methods are used to quantify the density and/or cover of algae and invertebrates along each transect. Swaths (or belt transects) and quadrats are used to estimate the density of species while uniform point contact (UPC) is used to estimate the cover of species. In addition to sampling biotic cover, the UPC method is used to estimate the percent cover of substratum type and relief. Quadrats are only done in southern California. Each transect is sampled by two or three divers with each diver conducting one technique.
Benthic surveys take place from approximately mid-June through Mid-August. Four to six divers complete the sampling of twelve benthic transects at a site in one day.
The purpose of the swath sampling is to estimate the density of conspicuous, solitary and mobile invertebrates as well as specific macroalgae. Individual invertebrates and plants are counted along the entire 30 m long x 2 m wide transect. Typically, a diver slowly swims one direction counting targeted invertebrates and then swims back counting targeted macroalgae. (See the swath datasheets for species targeted by this sampling method.) Cracks and crevices are searched and understory algae are pushed aside. No organisms are removed. Any organism with more than half of its body outside the swath is not counted. Transects are divided into three, 10 m segments.
Only Macrocystis plants taller than 1 m are recorded. The number of stipes at 1 m above the substrate on each Macrocystis plant is entered on the datasheet. Nereocystis, Pterygophora, Laminaria setchellii, and Eisenia arborea must have stipes taller than 30 cm to be counted. Only Cystoseira osmundacea plants greater than 6 cm wide are recorded. Laminaria farlowii must have a blade greater than 10 cm wide. All plants of Costaria, and Alaria are counted.
Very high densities of some species of invertebrates and algae prohibit enumeration along the entire length of a swath. We use a variable area sampling method in these cases. Within each 10 m increment (0-10, 10-20, 20-30) along a transect, divers enumerate organisms until the species threshold abundance (thirty individuals) or the end of the 10 m segment is reached. If the threshold abundance is reached, the diver records the distance they have sampled to that point along the transect and stops counting that species until the next 10 m segment.
Uniform point contacts (UPCs) are used to estimate the percent cover of species and reef attributes along each 30 m long transect. Divers record three types of information beneath 30 points located at every meter along the transect: 1) substrate type, 2) physical relief, and 3) percent cover of space-occupying organisms.
The percent cover of space-occupying organisms is estimated by recording what is directly under each point. The purpose is to re-create a two-dimensional, "photo style" representation of the percent cover of organisms that are directly attached to the primary substrate. Therefore, epiphytes, epizooids, and mobile organisms are not included. Algae whose blades are under the point but are attached somewhere else on the primary substrate are included. There are three exceptions that we have labeled "superlayers". If points overlay blades of Laminaria spp., the abundant sea cucumber Pachythone rubra or brittle stars, the blade or animal is removed and the species or substratum beneath it is recorded AND noted in the "superlayer" column on the datasheet. The UPC datasheets include categories for all non-motile, benthic invertebrates and algae.
Reef attributes are also noted for each point. Substrate type is recorded as sand, cobble (< 10cm diameter), boulder (10cm - 1 m diameter) or bedrock (> 1 m diameter). Physical relief is measured as the greatest vertical relief that exists within a 1-meter wide section across the tape and a 0.5-meter section along that tape that is centered over the appropriate point.
PISCO subtidal surveys are designed to rigorously sample temperate rocky reef communities. Consequently divers must be well trained in species identification and survey techniques. Diver's skill levels must meet a rigorous standard in order to participate in data collection for the surveys. PISCO ensures that all divers are competent in the survey techniques by providing intensive training and evaluation prior to the survey period. To allow rapid specialization by the divers, the survey is divided into two groups (Fish and Algae/ Invertebrates). Divers are trained in one to two weeks on each subject in an intensive classroom and field training course. PISCO training takes divers through species identification and survey techniques (e.g. size and abundance estimation, transect placement and sampling procedure). Divers may complete both courses and become trained in the entire survey technique in as little as two to four weeks of intensive training.
Below we have provided downloads of the materials used during PISCO survey training. Also, see the preliminary checklist for an outline of the necessary materials and equipment needed for conducting the surveys, which can be used as a guideline for equipment needed in the field.
Introduction to fish sampling protocol and overview (.ppt)
Example fish training syllabus (.doc)
Fish transect identification material
Common northern California fishes (.ppt)
Northern California fish identification quiz (.ppt)
Common southern California fishes (.ppt)
Southern California fish identification quiz (.ppt)
Daily fish training lectures (PowerPoint)
Introduction to Algae/Invertebrate sampling protocol and overview (.ppt)
Example algae/invertebrate training syllabus (.doc)
Swath transect identification material
Common northern California invertebrates (.ppt)
Common southern California invertebrates (.ppt)
Common California algae (.ppt)
Uniform Point Contact (UPC) identification material