The fisheries biology of two scallop species, Pecten maximus (l.) and Aequipecten opercularis (l.), in the waters around Shetland, Scotland.

  • Allen Campbell

    Student thesis: Doctoral ThesisDoctor of Philosophy (awarded by OU/Aberdeen)


    Commercial fishing for Pecten maximus and Aequipecten opercularis
    has taken place in Shetland since the late 1960’s and early 1970’s,
    respectively, with fluctuations in landings of both species during this time.
    Recognition of the importance that shellfish fishing contributes towards
    maintaining a diverse economy in a rural area, coupled with concerns in the
    1990’s about the potential for overfishing, prompted by reductions in the
    abundance of some shellfish species, the Shetland Shellfish Management
    Organisation Ltd. was formed, with a remit to implement local management of
    shellfish stocks, where necessary. The collection of biological data was started
    and the completion of log books begun in 1999 and 2000, respectively, to
    provide data to assess the species, with a view to their sustainable
    Von Bertalanffy growth parameters were determined for contemporary
    samples on both species and on historical samples of P. maximus. The
    asymptotic shell length, as a measure of growth, was examined in relation to
    the environmental variables of sediment composition and depth. Growth
    studies were carried out on juveniles to measure sub-annual growth.
    The gonadal condition through time in the adult stocks was assessed,
    changes in gonad condition were related to spawning activity by collection of
    spat on artificial collectors. Seasonal and spatial differences in yield of
    adductor muscle and gonad from experimentally derived, and commercial
    yield data, was analysed.
    The assessment of the fishery utilised fisher knowledge on the
    distribution of stocks. Catch Per Unit Effort and mortality rates data were
    calculated. The overall Spawning Stock Biomass was estimated for P.
    maximus using the swept area method. Long-term data from processing
    factories were incorporated into the fisheries assessment. The assessment
    indicates poor catches of A. opercularis for many years, and a recovery in
    abundance of P. maximus on some fishing grounds since the low catches
    experienced in 2000.
    Date of Award11 May 2010
    Original languageEnglish

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