• Login
    View Item 
    •   Home
    • University of Alaska Fairbanks
    • UAF Graduate School
    • Marine Biology
    • View Item
    •   Home
    • University of Alaska Fairbanks
    • UAF Graduate School
    • Marine Biology
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Browse

    All of Scholarworks@UACommunitiesPublication DateAuthorsTitlesSubjectsTypeThis CollectionPublication DateAuthorsTitlesSubjectsType

    My Account

    Login

    First Time Submitters, Register Here

    Register

    Statistics

    Display statistics

    Alternative sampling and estimation methods for multispecies trawl surveys

    • CSV
    • RefMan
    • EndNote
    • BibTex
    • RefWorks
    Thumbnail
    Name:
    Dressel.Sherri.2004.pdf
    Size:
    654.4Kb
    Format:
    PDF
    Download
    Author
    Dressel, Sherri Christine
    Metadata
    Show full item record
    URI
    http://hdl.handle.net/11122/4915
    Abstract
    Multispecies demersal trawl surveys are used in the United States and internationally to estimate the relative abundance of commercial and non-commercial fish species. Their usefulness for estimating species' abundance is often limited by the variance associated with estimates. This study implemented and evaluated alternative sampling and estimation methods, with the goal to incorporate additional sources of information for increased precision of individual species' estimates from multispecies trawl surveys. First, habitat characteristics and past spatial distributions of four flatfish species' density were incorporated into a multispecies trawl survey design conducted in Kalsin and Middle Bays, Kodiak Island, Alaska. Stratification by depth and percent sand produced estimates of relative abundance with lower CV s than those from unstratified sampling. Additional decreases in relative precision were generally not achieved by estimating the relative abundance of multiple species from regions of species-specific suboptimal habitat. Second, a poststratification technique was used to incorporate species-specific habitat characteristics and previous distributions of species' density into the estimation of species' abundance from the Kalsin and Middle Bays' trawl survey. Poststratification by habitat gave estimates with lower variance and/or less design-bias than an unstratified estimator for all species in all years. Poststratification by habitat and fish density produced estimates with the least design-bias for all species in all years and the lowest variance when stratum sample sizes were sufficient. Third, mixed model linear regression (MMLR), empirical Bayes (EB) and hierarchical Bayes (HB) estimation methods were used to incorporate historical trends of yellowfin sole, Limanda aspera biomass from the eastern Bering Sea trawl survey into annual biomass estimates. Using MMLR, EB, and HB methods resulted in biomass estimates that were less anomalous than survey estimates with respect to a linear regression trend. Estimates for all three methods had lower CV s than surveys in most years. The results of this thesis suggest that incorporating additional information into survey design and estimation can decrease the variability of survey estimates and/or correct for possible bias. Methods that can incorporate additional information, therefore, have the potential to improve survey assessments for management use.
    Description
    Dissertation (Ph.D.) University of Alaska Fairbanks, 2004
    Table of Contents
    Introduction -- Multispecies survey designs with habitat and fish density information -- Using poststratification to improve multispecies survey assessments : case study of juvenile flatfishes -- A comparison of models for incorporating multiple years of information into annual estimates of biomass from multispecies trawl surveys -- Conclusions.
    Date
    2004-05
    Type
    Dissertation
    Collections
    Marine Biology

    entitlement

     
    ABOUT US|HELP|BROWSE|ADVANCED SEARCH

    The University of Alaska is an affirmative action/equal opportunity employer, educational institution and provider and prohibits illegal discrimination against any individual.

    Learn more about UA’s notice of nondiscrimination.

    Open Repository is a service operated by 
    Atmire NV
     

    Export search results

    The export option will allow you to export the current search results of the entered query to a file. Different formats are available for download. To export the items, click on the button corresponding with the preferred download format.

    By default, clicking on the export buttons will result in a download of the allowed maximum amount of items.

    To select a subset of the search results, click "Selective Export" button and make a selection of the items you want to export. The amount of items that can be exported at once is similarly restricted as the full export.

    After making a selection, click one of the export format buttons. The amount of items that will be exported is indicated in the bubble next to export format.