Comparative Approaches to Predicting the Consequences of an Impending Re-Invasion: Top Predator Effects on Californian Nearshore Fisheries
Principal Investigators: Mark Carr (UCSC), Jim Estes (USGS), Tim Tinker (USGS), Phil Levin (NOAA), and Jennfier Caselle (UCSB)
Kelp forest ecosystem food webs vary markedly among three regions of the California Coast. The presence of sea otters (central California and San Nicolas Island), lobster and sheephead (Channel Islands and San Nicolas Island) all play a major role in mediating the dynamics of sea urchin and kelp abundance, and thereby directly or indirectly affect a suite of kelp associated species and fisheries.
Short Summary
The establishment of Marine Protected Areas and the impending re-establishment of sea otter populations across large portions of the California Coast create the potential for dramatic changes to kelp forest ecosystem dynamics, and fisheries yields. Researchers will employ empirical data and comparative analysis of three ecosystem modeling approaches to generate predictions of ecosystem response under the interacting effects of MPAs and otter predation. Insights gained from this study will potentially inform management decisions and help balance the conflicting objectives of protecting both sea otters and nearshore fisheries.
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Project Summary
Using an integrative two-fold comparative approach, we will perform a (i) spatiotemporal empirical comparison of the structure and dynamics of central and southern Californian nearshore ecosystems in order to (ii) parameterize and compare the performance of three ecosystem-based approaches for modeling the complex dynamics of these systems. Our goals are to develop analytical tools to facilitate ecosystem-based decision making and management, and to forecast how marine reserves and the impending reinvasion of sea otters to southern Californian waters will affect the region’s valued fisheries.
To accomplish these goals, we will synthesize and leverage an impressive array of preexisting data from spatially-extensive, long-term monitoring efforts (~140 sites spanning up to 30 years of semi-annual surveys) collected by ourselves and our colleagues at the USGS (PI’s Estes and Tinker), the PISCO consortium (PI’s Carr and Caselle), and the Channel Islands National Park Service. Along with our spatially-detailed 27-year-long times series on the range, density, and feeding habits of sea otters, our extensive spatiotemporal community data from the well-monitored network of MPA’s and reference sites of known age will provide the large-scale observational experiments needed to disentangle the effects of sea otters and MPAs on the structure and dynamics of California’s nearshore ecosystems and their fisheries.
The results will be incorporated into three different approaches for modeling, understanding, and predicting the short and long-term direct and indirect effects of sea otters and MPAs on the fisheries of Central and Southern California: (1) EcoPath with EcoSim, (2) Metabolic scaling theory, and (3) Loop Analysis. These three approaches span the modeling range of data requirements, ease of application, and assumptions, and vary greatly in the extent to which they simplify biology’s complexity and details. By employing multiple modeling approaches, we can compare model-based predictions for how the effects of MPAs and the impending re-invasion of sea otters communities will jointly and independently affect the productivity, dynamics, and resilience of these ecologically, socially and economically important communities.
The data synthesis, analyses, and modeling efforts that are proposed will provide the incisive ecosystem-based analyses and tools to facilitate the difficult management decisions that will be needed in dealing with the impending socioeconomic conflict between the government’s protection and supported re-establishment of a federally threatened species, and the preservation and governance of numerous valued fisheries.
The proposed comparisons will advance our understanding of complex ecosystem processes in central and southern CA kelp forests, including the interaction between bottom-up and top-down processes, and how these are influenced by geographic variation in key structural and functional attributes (including changes in ocean climate). On a more practical level, this work will result in (1) a set of analytical tools and a suite of effective and transferrable ecosystem-based indicators to assess the status, thresholds and resiliency of nearshore temperate reef ecosystems; and (2) an ensemble collection of ecosystem-based predictions of short- and long-term community dynamics, including resiliency to environmental change and to commercially and recreationally valued kelp forest fisheries. These two products will be of enormous value for informing the design of monitoring and evaluation programs for MPAs, and will be especially useful for fisheries managers by helping them predict and best accommodate the impacts of the re-invasion of sea otters into southern CA kelp forests.