Intertidal Mussel (Mytilus) Data from Prince William Sound, Katmai National Park and Preserve, and Kenai Fjords National Park

FIELD: Sampling was conducted in sheltered rocky habitats within regions of Alaska including: Kenai Peninsula (KEP; Kenai Fjords National Park), Alaska Peninsula (AKP; Katmai National Park and Preserve), and Prince William Sound (PWS; northern, western, and eastern Prince William Sound). Study site locations are described in the "Monitoring Site Locations" data release: https://doi.org/10.5066/F78S4N3R (Coletti et al. 2017). Field measurements of transect lengths were conducted with 50-meter fiberglass measuring tapes demarked in meters/centimeters/millimeters. The tape was stretched along the shoreline parallel to the water's edge from the left edge marker at the mussel bed's boundary to the right edge marker. The sampling team then calculated the position of placement for 10 vertical transects using a prepared spreadsheet. The initial vertical transect was based on a random number between 0.00 and 4.75. Nine subsequent vertical transects were established at 5-meter intervals from the initial random location. For the vertical transects, a surveyor's tape was placed perpendicular to the baseline transect. The length of the vertical transects varied with the size and shape of the bed. The length of each vertical transect from the upper end where it crosses the baseline (referred to as zero) to the lower end of the mussel bed (or zero tidal elevation if bed continues below MLLW) were recorded on a data sheet. When the distance above or below the horizontal transect to the first mussel beneath the tape was greater than 1.0 meter, the length for the vertical transect was set at zero (Bodkin et al. 2016). The vertical transect measurements are used to estimate the size, or area of the mussel bed. The upper and lower limits of the mussel bed are defined by the presence of mussels immediately beneath each of the vertical transect tapes. To determine placement of the quadrat, each of the vertical transect lengths were then multiplied by an independent random number between 0.00 and 1.00. The resulting number identified the location along the vertical transect where the quadrat was placed, and the core sampled for mussel density and size. Sampling included core samples to estimate the density of all mussels and quadrat samples of variable size, to estimate the density and size distribution of mussels greater than or equal to 20 millimeter in length. The cores consist of a 120-millimeter length of 48 millimeter inside diameter ABS or similar pipe. Within this core all mussels are removed. Each mussel is then counted, and density calculated by dividing by the area of the core (Bodkin et al. 2016). Next, if mussels are relatively abundant near a core sample, a small quadrat can be selected, as small as 6.25-centimeter x 6.25 centimeter. If approximately 20 mussels greater than or equal to 20 millimeters are present, then all mussels greater than or equal to 20 millimeters within the 6.25-centimeter quadrat were collected. If this smallest quadrat provides fewer than 10-15 large mussels than this quadrat size was doubled by flipping the quadrat once to the right. This process is repeated with a 25 x 25-centimeter quadrat, following the same procedures up to a 1-meter x 1 meter quadrat. At this point all mussels greater than 20 millimeters within the defined quadrat are collected (Bodkin et al. 2016). Mussel sizes were measured at the longest point of the shell. Dial calipers are read to the nearest tenth of a millimeter and rounded to the appropriate millimeter. Calipers are checked and zeroed prior to measuring. Counts of mussels from cores are calculated by summing the number of mussels in each size bin (i.e., less than 20mm or greater than 20 mm) for 2014 and onwards, or by hand counting.

LAB: Mussels larger than 20 millimeters were collected for size frequency and density calculations. These were measured in the lab and the data entered directly into a Microsoft Access database. The null "." is entered for the measurement of mussels that have been crushed in the collection process and are deemed un-measureable. The field crew and then a field data manager review the field and lab data sheets for missing, illegible, or confusing entries and correct any issues. The overall site level data, substrate data, 20mm count data and primary core count data are checked against the field data sheets and also checked row by row and cell by cell for accuracy and completeness. Basic descriptive statistics were run on the data in the 20 mm size data and core size frequency data sets to look for outliers or values inconsistent with the protocol (for example only mussels greater than or equal to 20 millimeters should be in the 20 mm size data set). Additional details are provided in the entity and attribute section. Count and measurement datasets are checked against the field data sheets and lab data sheets for completeness and logical consistency, data is checked for outliers.

LITERATURE CITED: Dean, T.A., Bodkin, J.L., Coletti, H.A., 2014, Protocol narrative for marine nearshore ecosystem monitoring in the Gulf of Alaska: Version 1.1. Southwest Alaska Inventory and Monitoring Network. Natural Resource Report NPS/SWAN/NRR - 2014/756. National Park Service, Fort Collins, Colorado. https://irma.nps.gov/DataStore/Reference/Profile/2206501. Accessed 10 April 2024. Bodkin, J.L., Dean, T.A., Coletti, H.A., Ballachey, B.E., 2016. Mussel bed sampling: standard operating procedure, v. 1.2, Southwest Alaska Network. Natural Resource Report NPS/SWAN/NRR—2016/1175. National Park Service, Fort Collins, Colorado. https://irma.nps.gov/DataStore/Reference/Profile/2228023. Accessed 10 April 2024. Coletti, H.A., Kloecker, K.A., Bodkin, J.L., Dean, T.A., 2017. Gulf Watch Alaska Nearshore Component: Monitoring Site Locations from Prince William Sound, Katmai National Park and Preserve, and Kenai Fjords National Park: U.S. Geological Survey data release, https://doi.org/10.5066/F78S4N3R