Western Society of Naturalists Conference, Tacoma, WA, 2018
Best Presentation Award in Community/Ecosystem Ecology
Smith JG, T Tinker, MH Carr, S Lyon, M Staedler, J Tomoleoni. (2018). Golden gonads in sea otter country: how sea urchin condition influences patch selection by sea-otters.
Abstract: Along the central coast of California, active sea urchin grazing recently shifted an expansive kelp forest to a mosaic landscape comprised of patchy forests interspersed with sea urchin barrens void of kelp. In forested patches, sea urchins are well fed and contain high energy content through gonad production, while those in barrens patches are starved and lack fully developed gonads. We examined how this variation in prey condition influences patch selection by a major urchin predator, the Southern sea otter (Enhydra lutris). Specifically, the condition (i.e., gonad index) of purple sea urchins (Strongylocentrotus purpuratus) was examined to determine how prey quality influences the foraging behavior of sea otters. We conducted extensive shore observations of otter foraging behavior, combined with subtidal surveys at focal urchin patches that were paired with laboratory evaluations of urchin gonad condition. Additional subtidal surveys were conducted throughout the region to track changing urchin demographics (e.g., density, size structure, gonad index) and the extent of barren-forest patches across the study area. Results from our two-year study indicate that sea otters preferentially target gravid urchins inside of forested patches and mostly ignore those in urchin barrens. We demonstrate a logistic relationship between otter patch selection and gonad index. Our findings suggest that prey quality is an important consideration for evaluating the potential strength of trophic cascades and the ability of predators to control herbivore populations.
Western Society of Naturalists Conference, Tacoma WA, 2014
Smith JG, Lindholm J, Knight A. (2014). Vertical distribution and composition of demersal fish communities along the walls of the La Jolla-Scripps Canyons.
Abstract: Ecologists have long recognized the importance of characterizing fish-habitat associations, especially for the design and implementation of marine protected areas. Despite this importance, little is known about fish distribution and habitat suitability in submarine canyons which have proven difficult to sample adequately. The active continental margin of the California coast is cut by eight submarine canyons, many of which extend from the shore to the deep abyssal plain. We sampled the demersal fish communities in two of those canyons, the La Jolla Canyon in the San-Diego-Scripps Coastal Marine Conservation Area (SMCA), and the Scripps Canyon the Matlahuayl State Marine Reserve (SMR), in depths ranging from 20-300m using a remotely operated vehicle (ROV). Species composition, abundance, and habitat (slope and complexity) were quantified and mapped using ArcGIS. Thirty-seven species of demersal fishes representing 17 families were obtained from 21 vertical transects along the canyon walls. Species composition was assessed in 15 depth-stratified bins (20m per bin) along, and to either side, of the canyon walls. Although sampling effort decreased with depth, species composition (richness/m) increased along this gradient. Ongoing analyses of canyon dynamics will provide more detailed insight to factors that facilitate demersal fish communities.