The distribution of demersal fishes over heterogenous seafloor habitats : an application of landscape ecology to video imagery collected in a central California state marine conservation area
Thesis (M.S.) Division of Science and Environmental Policy
Using landscape ecology approaches, this study investigated the importance of structural patterning in the seafloor landscape and the scales at which demersal fishes associate with different habitats. The following document describes the project in three parts: 1) The circumstances surrounding the management of the study site and the methodological approaches used; 2) The analytical framework and results; 3) Potential applications of these results in management. By describing the landscapes across which demersal fish are distributed at the Piedras Blancas State Marine Conservation Area (PBSMCA), within the Monterey Bay National Marine Sanctuary, we evaluated fish-habitat associations in the context of other central California deepwater studies. Quantifying and monitoring the distribution of fishes over the habitats at this site is critical to understanding how this marine protected area (MPA) may function as a conservation measure. Imagery surveys are ideal for collecting data on seafloor habitats and observing fishes in these habitats; these data are becoming an increasingly important contribution to marine conservation management. We examined imagery collected at the PBSMCA with a towed camera system. Surveys were conducted in 2007 and 2008 in water depths ranging from 30-120 m. Video imagery gathered with the sled was viewed as a set of non-overlapping video quadrats (frames). We compared generalized linear models to estimate the probability of response (detection) of selected demersal fish groups to a number of habitat variables, assuming a uniform probability of detection. Results suggested that, for all fish groupings, there is evidence that seafloor substrate plays a very strong role in determining distributions. Depth also played an important role, while biogenic structure and soft-sediment bedforms were rarely of importance to the distributions. Our results are consistent for the most part with fish distribution studies conducted at other sites within the central California region. These results highlight the importance of using imagery to collect monitoring data about marine landscapes. Use of a simple, low-cost camera system enabled us to address complex ecological questions about demersal fish-habitat associations across a heterogeneous landscape and provided useful results in the form of baseline data to MPA managers and site characterization to the Monterey Bay National Marine Sanctuary.