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RESEARCH microchemistry Motivation MotivationThe intent of this research project is to identify the paths and sources of pelagic larvae that eventually recruit to the benthic communities on which PISCO research focuses. By understanding these paths and sources, we can identify the proper scale for oceanographic studies and determine the extent of connections between local marine populations. This information is a vital step in designing effective management and conservation schemes. The specific technique that we are developing involves the use of Research Questions
ApproachPISCO UCSB is taking the organizational role in attacking these questions. In addition to microchemistry, our efforts also focus on population genetics. The microchemistry research project consists of four interrelated efforts, each of which builds on the others. We are using isolated island systems as testing grounds for these techniques, because both the sources and destinations of young are much more discrete and identifiable here than along mainland coasts. We are proceeding from island systems to a study of U.S. West Coast island-mainland connections, focusing on two of the northern Channel Islands, Santa Cruz and Santa Rosa islands. At the same time, we are developing research projects at two critical areas along the mainland coast: Point Conception and Monterey Bay. Finally, we are instituting a large-scale, lab-based validation program intended to specify the correspondence between environmental conditions (trace elements in seawater and food, temperature, and salinity) and the signature laid down in the larval structure. Research Findings Up and down the West Coast, PISCO is building a record of source signatures (taken from the otolith core) corresponding to larval recruitment events under different oceanographic regimes. In a major advance, we have developed the means to read the trace-elemental signatures in these tiny structures using Inductively Coupled Plasma (ICP)-mass spectrometry. The results of our preliminary geographic analyses are striking. For the kelp rockfish (Sebastes atrovirens), for example, elemental signatures derived from pre-release larvae are consistent across broods within a site, and distinctly different between sites (in this case, mainland vs. Santa Cruz Island, as well as between two mainland sites, Goleta and Ellwood, less than 20 km apart). Data for invertebrates show similar promise. UCSB Graduate Student Danielle Zacherl has shown that statoliths of Kellet's whelk (Kelletia kelletia) larvae still in egg masses show clear differences between samples taken from north and south of Point Conception. Thus, we have evidence suggesting that elemental signatures in otoliths and statoliths differ over relatively small spatial scales, and that these differences may be stable over extended periods. Research during the next year will attempt to establish an "atlas" of core signatures of rockfish and mollusks from a large area of the Pacific coast. West Coast recruitment dynamicsPISCO also is using microchemistry techniques to understand recruitment dynamics along the West Coast. We are collecting juvenile rockfish during the winter/spring recruitment season in nearshore waters surrounding the Channel Islands and within Monterey Bay. Otoliths from recruits are characterized by (1) water mass into which the larva was released initially, as indicated by the signature in the otolith core regions, (2) water mass where the larva resided during the pelagic phase, and (3) water mass at the point of settlement. Otoliths of adults from settlement and potential source populations provide information about geographic differences in environmental signatures and temporal differences in the pattern of signatures. Tracking adult movement: a complimentary studyIn addition to tracking larval recruits, in a small pilot project, PISCO and its collaborators are utilizing new technologies to track adult fish movements too. Advances in acoustic telemetry offer methods for tracking fish movements on daily to annual time scales. Through a collaborative project with Christopher Lowe and graduate student Darin Topping of California State University, Long Beach, with supplemental funding from California Sea Grant, we are using these techniques to assess the effectiveness of marine reserves in protecting the juveniles and adults of harvested species. In 2001 21 fish were acoustically tracked in the Catalina Island Marine Reserve (12 kelp bass and 9 sheepshead wrasse). Surprisingly, home ranges were significantly smaller than previously thought; kelp bass virtually never moved outside reserve boundaries and sheepshead wrasse rarely did so. To determine the generality of this pattern, we are expanding the movement studies to other species and extending the duration of the observations to track seasonal movements using acoustic monitoring. In the upcoming year PISCO and our collaborators will acoustically monitor dozens of fish at Anacapa Island (including sheepshead, cabezon, and ocean whitefish) and we are investigating the feasibility of monitoring California spiny lobster. Our findings on the movements of juveniles and adults are a first and important step towards understanding the design and function of marine reserves. By Bob Warner, Principal Investigator, and Renee Davis-Born, and Lydia Bergen, Policy Coordinators |
structures contained within the bodies of pelagic larvae. These structures (otoliths in fish, statoliths and protoconchs in invertebrates) grow as the larva grows and incorporate trace elements from the environment. These environmental signatures can then be used to identify the routes that larvae have traveled, from source population to settlement. 
Signatures from the outer edge of adult otoliths show a similar pattern of within-site consistency and between-site differences. Importantly, signatures from otolith "transects" taken from the edge of the adult otolith inward (covering 3-6 months of deposition) are similar to edge signatures, suggesting some temporal stability in local signals. 
To conduct studies of recruitment dynamics, we have developed techniques to analyze the core regions of otoliths and statoliths of newly-arrived recruits. PISCO studies already are uncovering patterns in otolith signatures. For example, core regions of Kellet's whelk statoliths show trace-metal enrichment and distinct geographic differences (i.e., north and south of Pt. Conception) in elemental signatures, suggesting different source populations. Elemental signatures from otolith cores of newly settled recruits of kelp rockfish also show "families" of signatures, suggesting a limited set of source populations.