• Login
    View Item 
    •   Home
    • University of Alaska Fairbanks
    • UAF Graduate School
    • Fisheries
    • View Item
    •   Home
    • University of Alaska Fairbanks
    • UAF Graduate School
    • Fisheries
    • 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

    Length-based models and population analyses for northern shrimp Pandalus borealis Krøyer

    • CSV
    • RefMan
    • EndNote
    • BibTex
    • RefWorks
    Thumbnail
    Name:
    Fu.Caihong.2000.pdf
    Size:
    4.725Mb
    Format:
    PDF
    Download
    Author
    Fu, Caihong
    Metadata
    Show full item record
    URI
    http://hdl.handle.net/11122/5120
    Abstract
    The lack of basic knowledge on stock dynamics o f northern shrimp Pandalus borealis, a protandric hermaphrodite, has caused difficulty in regulating fishing effort on a scientific basis and in understanding potential causes behind population fluctuations and collapses. Previous length-based population models (LBMs), developed for other species, are undesirable primarily for two reasons: (1) individual cohort dynamics are masked; (2) variations in annual natural mortality (M) are ignored. This research was primarily aimed at developing a more advanced LBM that provides estimates of parameters such as recruitment (R), fishing mortality (F) and especially annual M. Simulation-estimation experiments were conducted to evaluate model performance. Despite model complexity, annual M can be well estimated provided measurement errors in survey biomass estimates are low. The common assumption of constant M created biased parameter estimates. Estimated M of P. borealis in Kachemak Bay, Alaska increased steadily in the 1980s. Retrospective projections showed that the increasing trend in M in the 1980s resulted in the population collapse. The ultimate goal o f stock assessment is to develop sound harvest strategies. With the widely observed abundance fluctuations in shrimp populations, it is impossible to manage solely based on conventional methods, such as maximum sustainable yield (MSY). Thus, harvest strategies were compared under various situations o f M and R. With M increasing over time, it is important to execute threshold management, i.e., closing the fishery at population levels below a threshold value. Simulations indicated that overfishing caused by underestimated M or overestimated R can be greatly alleviated if the population is sampled once every year. Life history aspects of sex change, growth, M, and their seasonal variations were also incorporated into the LBM. Populations with protandrous animals are likely to be subject to recruitment overfishing; merely protecting older females while allowing high exploitation on younger males can lead to population collapse. Fishing after spring egg hatching is superior to fishing after mating and egg extrusion in fall when F is high. In summary, the length-based model developed here provided a convenient framework for understanding population processes and harvest strategies and should be useful for a variety of hard-to-age species.
    Description
    Dissertation (Ph.D.) University of Alaska Fairbanks, 2000
    Table of Contents
    1. Introduction and overview -- 1.1. Distribution and fisheries worldwide -- 1.2. Review of stock assessment -- 1.3. Overview of biological data pertinent to assessment of P. borealis -- 2. Estimability of natural mortality and other population parameters in a length-based model: Pandalus borealis Krøyer in Kachemak Bay, Alaska -- 3. Retrospective projection using Monte Carlo simulation: an application of a length-based model to Kachemak Bay northern shrimp -- 4. Analyses of harvest strategies for Pandalus shrimp populations -- 5. The role of sex change, growth, and mortality in Pandalus population dynamics and management -- Summary -- Bibliography -- Appendix 1. Detailed descriptions of the length-based population model for chapter 2 -- Appendix 2. Details of the length-based model for chapter 3.
    Date
    2000-08
    Type
    Dissertation
    Collections
    Fisheries

    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.