Scientists from the NWFSC collaborate with NMS staff scientists and vessel operators to conduct annual subtidal SCUBA surveys in kelp forests within the coastal waters of Olympic Coast National Marine Sanctuary. Researchers access study sites from La Push and Neah Bay, WA during late summer using two research vessels operated in tandem: OCNMS’s 40’ R/V Tatoosh and NWFSC’s 21’ dive boat, R/V Minnow. The visual (SCUBA) dive surveys, derived from PISCO monitoring protocols, concentrate on five focal sites at two depths (5 and 10-m) to measure fish density, macroinvertebrate density, kelp density, and substrate type, rugosity, and cover.
We conducted SCUBA surveys at five kelp forest sites along the northern half of coastal Washington once annually in late July or early August from 2015-2019. Most sites fall within the Olympic Coast National Marine Sanctuary (OCNMS, designated in 1994). SCUBA divers surveyed benthic communities along 30 x 2 m belt transects in kelp beds at depths of 5 and 10 m using a quantitative standardized monitoring protocol (Pondella et al. 2019; Claisse et al. 2012), targeting 12 transects per depth zone and site in a random stratified sampling design. Divers collected information in four categories: fish, large mobile invertebrates, canopy-forming kelps, and substrate.
For fish data, divers visually assessed abundance and total length of fish observed within a belt transect and within 2m off the bottom for individuals greater than 5cm total length. Rockfish species were recorded for all observations regardless of size. Underwater visibility was measured between dive team members at each transect. Observations of these mobile species, since accuracy is dependent upon visibility, were included in analyses when underwater visibility was greater than 3m.
Large mobile invertebrates were enumerated for individuals greater than 2.5cm in diameter or width, including under prostrate algae and within bottom topography and on algae up to a height of 1m above the substrate. This category included species of sea urchins, sea star, sea cucumbers, crabs, bivalves, nudibranchs, etc. We included only species that were easily identifiable to avoid concerns about the detection of cryptic species. For abundant species the transect was broken into 10m segments and the distance at which 30 individuals were counted per segment was noted, to be used in expansion calculations. We also recorded sea urchin test diameter and sea star radius sizes. In some instances, we grouped species into functional taxonomic categories for analysis.
We counted canopy-forming kelp species within each transect area. For Macrocystis pyrifera the stipes were counted when greater than 1m in height. Nereocystis luetkeana and Pterygophora californica plants with stipes greater than 30cm in height were included, along with other brown algae species greater than 30cm in overall length. We again used the segment subsampling for abundant species described for invertebrate species.
Substrate data was collected at each meter mark along the transect in a uniform point contact (UPC) survey method. We noted substrate composition type (bedrock, boulder, cobble, sand), categorical degree of relief, and the organism responsible for holding primary space on the substrate at that location.
Pondella, D.J. II, S.E. Piacenza, J.T. Claisse, C.M. Williams, J.P. Wiliams, A.J. Zellmer, and J.E. Caselle. 2019. Assessing drivers of rocky reef fish biomass density from the Southern California Bight. Mar Ecol Prog Ser. 628:125-140.
Claisse, J.T., D.J. Pondella II, J.P. Williams, J. Sadd. 2012. Using GIS mapping of the extent of nearshore rocky reefs to estimate the abundance and reproductive output of important fishery species. PLOS ONE. 7:e30290.