Date

Fall 2023

Document Type

Master's Thesis (Open Access)

Degree Name

Master of Science (M.S.)

Department

Moss Landing Marine Laboratories

Abstract

Temperate rocky reefs feature a mosaic of complex macrohabitat features which host a variety of demersal fish species. Giant kelp forests add considerable vertical structure to rocky reefs, including macrohabitats extending from the reef to the upper water column. Much of what we know about temperate communities derives from shallow SCUBA surveys in which divers record observations using underwater visual census (UVC) techniques. Increasingly, these communities are being studied with video techniques first utilized in deeper water. While UVC provides immediate data on fish communities and requires no additional technology either for data collection or post-processing, imagery captures the fine-scale associations between fish specific habitat features that elude UVC techniques. While traditional video cameras constrain the field of view available to a UVC diver, 360˚ cameras record everything in all directions, eliminating the need to selectively survey one direction underwater. However, questions remain as to how data derived from 360˚ video transects compare to the more well-established UVC transects, particularly in complex environments. My primary research objective was to examine the trade-offs associated with 360˚ video and UVC when quantifying attributes of the demersal fish community across multiple sites and macrohabitat types. I performed SCUBA dives at four sites around the Monterey Peninsula in central California. Pairing UVC and 360˚ video, I recorded fish counts along 30 meter demersal transects. Richness, diversity, abundance, and density of fishes from UVC and 360˚ video were compared statistically with two-way analysis of variance (ANOVA) and non-metric multidimensional scaling (NMDS). Results indicate that within fish-habitat guilds, counts of species were similar between methods at all macrohabitats and at most sites. 360˚ video and UVC produced similar results with respect to species richness and diversity. At every scale, UVC density was always significantly greater than 360˚ video density. Count per meter independent of volume was greater when measured from 360˚ video for all fish combined, but this result was less clear when fish were separated into habitat guilds. Both methods were plotted similarly and revealed comparable site-specific trends in community structure when ordinated via nMDS. These results suggest that despite higher research costs and some data caveats, 360˚ video transects can be incorporated into temperate subtidal reef monitoring without compromising data quality. 360˚ video techniques can supplement traditional survey methods within nearshore environments to monitor shallow marine protected areas and fisheries resources.

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