Sökning: "vendace"

Hittade 5 avhandlingar innehållade ordet vendace.

  1. 1. The dynamics in harvested populations

    Författare :Anders Wikström; Biologiska institutionen; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; fluctuations; temporal; state-space; Harvest; cod; vendace; elasticity; stage-structured; stochastic; growth-rate; Baltic Sea; Bothnian Bay;

    Sammanfattning : We are interested in the effect of harvesting on population fluctuations and for that purpose we develop and analyze an age-structured model where recruitment is a stochastic process and the adult segment of the population is harvested. When a constant annual harvest is taken the coefficient of variation of the adult population increases for most parameter values due to the age truncation effect, i. LÄS MER

  3. 2. Habitat selection and indirect interactions in fish communities : mechanisms to explain spatial distribution of perch, roach, and vendace

    Författare :Ulrika Beier; Sveriges lantbruksuniversitet; Sveriges lantbruksuniversitet; []
    Nyckelord :LANTBRUKSVETENSKAPER; AGRICULTURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES;

    Sammanfattning : To increase the understanding of freshwater lake ecosystems, I have studied the habitat selection of perch (Perca fluviatilis L.), roach (Rutilus rutilus (L.)), and vendace (Coregonus albula (L.)). LÄS MER

  4. 3. Habitat use in fish communities : size- and environment-dependent mechanisms affecting biotic interactions and population regulation

    Författare :Ulrika Beier; Sveriges lantbruksuniversitet; Sveriges lantbruksuniversitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES;

    Sammanfattning : Through the influence of abiotic factors, the habitat use of organisms affects their metabolism as well as other species- and size-dependent individual-based rates. The habitat-specific performances of individuals interacting in different habitats thereby affect biotic interactions. LÄS MER

  5. 4. Flipping the pyramid : lessons from converting top-down management of bleak-roe fishing

    Författare :Carl Rova; Luleå tekniska universitet; []
    Nyckelord :SAMHÄLLSVETENSKAP; SOCIAL SCIENCES; Political Science; Statsvetenskap;

    Sammanfattning : The fishing of vendace (Coregonus albula), in the northern part of the Gulf of Bothnia, is a good illustration of the presumption that institutional arrangements which are too inflexible to cope with changing ecological conditions are unlikely to prosper. The aim of this thesis is to contribute to the development of a better understanding of governance in a relatively small and clearly defined, but complex common-pool resource system. LÄS MER

  7. 5. Natural resources and institutional performance : linking social and ecological systems in fisheries

    Författare :Carl Rova; Luleå tekniska universitet; []
    Nyckelord :SAMHÄLLSVETENSKAP; SOCIAL SCIENCES; Political Science; Statsvetenskap;

    Sammanfattning : In times of resource scarcity, the management system should be able to adjust, thus enabling it to respond and reorganise when changes in the ecosystem occur. For a successful resource management, ecological resilience must be combined with institutional resilience. LÄS MER