We used a remotely operated vehicle to investigate landscape-scale patterns of subtidal drift material and invertebrates within a 60-km 2 marine basin in Washington State. Specifically, we quantified the distribution and abundance of drift macrophytes (seaweed and seagrass) and four macroinvertebrate species across depth and habitat type to depths of 170 m. Drift macrophytes were present on 97% of all video segments deeper than 30 m, with large drift piles particularly associated with low-angle habitats at depths exceeding 70 m. Two commercially harvested species (Strongylocentrotus franciscanus and Pandalus platyceros) that feed directly on drift material appear to be distributed in space (depth and substrate type) so as to maximize access to drift macrophyte food resources, according to their respective feeding modes. Basin shape and depth drive the landscape-scale distribution of drift material and indirectly the consumers that feed on it. The export of large amounts of detritus derived from nearshore macrophyte production into deep-water habitats likely fuels extensive secondary production in these aphotic zones.Nearshore macrophyte production contributes a substantial amount of carbon to high-latitude marine ecosystems. Much of this production is exported as macroscopic detritus (i.e., drift) to adjacent deeper, aphotic habitats (Mann 1988;Okey 2003). Despite the absence of endogenous carbon sources, these deep subtidal environments (DSE) often support considerable secondary productivity (Vetter 1995;Vetter and Dayton 1999;Britton-Simmons et al. 2009) and are a key source of commercial fisheries worldwide (Food and Agriculture Organization 2007). However, subtidal population and process-focused studies are typically constrained to depths accessible by divers and to relatively small spatial scales. In the present study, we examined the landscape-scale distribution and abundance of drift macrophytes and select invertebrates within the San Juan Archipelago (SJA), a 60-km 2 marine basin, in Washington State.Subtidal drift macrophytes in our system are produced by a diverse assemblage of nearshore seaweeds and seagrasses that diminish in abundance below 18 m and become rare by 23-m depth (Britton-Simmons et al. 2009) due to light limitation. Most subtidal drift biomass is contributed by kelps (order Laminariales) with substantial contributions also made by orders Fucales and Desmarestiales. Seagrasses (mostly Zostera marina) are present in the drift but contribute relatively little to biomass (BrittonSimmons et al. 2009). Drift material is an excellent food resource since it tends to have elevated levels of nitrogen (Mann 1988) and diminished levels of defensive chemicals (Duggins and Eckman 1997). This resource could be important for driving marine secondary productivity in DSE, but we know little about its distribution among depths and habitat types within DSE. Moreover, we need key information about where this material is distributed relative to the taxa that could be using it (Suchanek et al. 1985;Ve...
Estimating a population's growth rate and year‐to‐year variance is a key component of population viability analysis (PVA). However, standard PVA methods require time series of counts obtained using consistent survey methods over many years. In addition, it can be difficult to separate observation and process variance, which is critical for PVA. Time‐series analysis performed with multivariate autoregressive state‐space (MARSS) models is a flexible statistical framework that allows one to address many of these limitations. MARSS models allow one to combine surveys with different gears and across different sites for estimation of PVA parameters, and to implement replication, which reduces the variance‐separation problem and maximizes informational input for mean trend estimation. Even data that are fragmented with unknown error levels can be accommodated. We present a practical case study that illustrates MARSS analysis steps: data choice, model set‐up, model selection, and parameter estimation. Our case study is an analysis of the long‐term trends of rockfish in Puget Sound, Washington, based on citizen science scuba surveys, a fishery‐independent trawl survey, and recreational fishery surveys affected by bag‐limit reductions. The best‐supported models indicated that the recreational and trawl surveys tracked different, temporally independent assemblages that declined at similar rates (an average of −3.8% to −3.9% per year). The scuba survey tracked a separate increasing and temporally independent assemblage (an average of 4.1% per year). Three rockfishes (bocaccio, canary, and yelloweye) are listed in Puget Sound under the US Endangered Species Act (ESA). These species are associated with deep water, which the recreational and trawl surveys sample better than the scuba survey. All three ESA‐listed rockfishes declined as a proportion of recreational catch between the 1970s and 2010s, suggesting that they experienced similar or more severe reductions in abundance than the 3.8–3.9% per year declines that were estimated for rockfish populations sampled by the recreational and trawl surveys.
Small remotely operated vehicles (ROVs), sometimes described as low-cost (<$150,000) ROVs, have become valuable tools in the study of marine organisms and their habitats. The versatility and relative simplicity of these vehicles is enabling scientists and fishery managers to develop a better understanding of the marine ecosystem that has not been possible using conventional survey methodologies. The ability to work at depths beyond the reach of scuba divers and in complex habitats inaccessible to trawl surveys is helping to "fill the information gap" between nearshore and deep offshore habitats, allowing for the development of more comprehensive management strategies of the ocean's resources.Small ROVs are especially suited for use by natural resource agencies and academic institutions operating on limited budgets with minimal resources. In calm, nearshore conditions, a small ROV can be operated from vessels as small as 6 m with a minimum of equipment and crew. In contrast, conducting safe, quantitative surveys with a small ROV in more extreme marine environments increases the complexity of the operation and requires additional equipment and personnel to ensure success. This paper focuses on the technical aspects of designing and conducting shallow-water (<200 m) surveys with a small ROV, based on our experience using a Deep Ocean Engineering Phantom HD2+2 ROV in San Juan Channel, Washington. Topics addressed include equipment, navigation and tracking, deployment protocols, tether management, camera calibration, survey design, data collection, hazards and safety, transect length and width, and recent technological developments.
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