Seamount communities were sampled using video transects collected by MBARI’s ROV Tiburon. Video transects were conducted using high definition (HD) video cameras and recorded onto D5-HD video tape. We collected specimens for taxonomic determinations using ROV manipulator arms and suction samplers. Video transects were annotated in detail using MBARI’s Video Annotation and Reference System, VARS (Schlining & Jacobsen-Stout 2006).
All megafauna were identified to the species level or equivalent by trained video annotators using in situ video frame grabs and/or voucher specimens that were identified by taxonomists (see Acknowledgements). Every effort was made to assign organisms that were morphologically distinct (i.e. morphospecies) with an appropriate Latin binomial. Voucher specimens were not collected for organisms that could be identified easily from video and are known from the Californian shelf and Monterey Canyon. In some instances, voucher specimens were not obtainable and video frame grabs, digital still images, and/or video segments of the organisms in question were reviewed by taxonomists with expertise in that particular taxonomic group. Recently, the usage of video and still images in biogeographic, ecological, and taxonomic studies of deep-sea species has become a common and vital tool for describing both species and faunas in habitats logistically difficult to sample like the deep sea (Matsumoto et al. 2003; Haddock 2004; Braby et al. 2007; Cairns 2007; Lundsten et al. 2009a,b; Williams & Lundsten 2009).
A total of 33 quantitative video transects were collected at Davidson Seamount in 2006 (Fig. 1). The total number of transects reflects the maximum number feasible during our total allotted remotely operated vehicle dives. Transect placement was chosen to maximize depth coverage, minimize ship and ROV transit time, and satisfy multiple dive objectives spanning across several research projects. Two parallel, 640-nm red lasers were placed 29 cm apart and used to estimate transect width. Transect length was calculated in ARCVIEW® 3.2 using the Animal Movement Analysis Extension, Version 2, which was used to calculate successive distance between transect start and end points (Hooge & Eichenlaub 1997). Transect distance ranged from 93 m to 444 m with the mean and majority of transects being near 200 m and transect width between 1 and 3 m. For each transect the total area was calculated and included as a factor in the analyses. For multivariate analyses, density per meter squared was used to calculate similarities using abundance. Davidson Seamount was sampled over 96.8% of its depth from summit at 1246 m to base at 3289 m (transects at 1299, 1477, 1546, 1602, 1655, 1664, 1671, 1674, 1677, 1681, 1692, 1693, 1698, 1719, 1719, 1725, 1725, 1742, 1747, 1764, 1769, 2043, 2219, 2464, 2491, 2664, 2675, 2790, 2927, 2949, 3068, 3190, and 3276 m). More on the features, geology, and habitat of Davidson Seamount can be found in Davis et al. (2002).