Sökning: "fish biomass"

Visar resultat 1 - 5 av 70 avhandlingar innehållade orden fish biomass.

  1. 1. Climate change impacts on production and dynamics of fish populations

    Författare :Per Hedström; Pär Byström; Jan Karlsson; Peter Eklöv; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Temperature; terrestrial dissolved organic carbon; light extinction; GPP; recruitment; winter mortality; metabolism; cohort competition; fish production; fish biomass;

    Sammanfattning : Ongoing climate change is predicted to increase water temperatures and export of terrestrial dissolved matter (TDOM) to aquatic ecosystems influencing ecosystem productivity, food web dynamics and production of top consumers. Ecosystem productivity is mainly determined by the rates of primary production (GPP) in turn controlled by nutrients, light availability and temperature, while temperature alone affect vital rates like consumption and metabolic rates and maintenance requirements of consumers. LÄS MER

  3. 2. Distribution and activity of pelagic fish - acoustic studies in the Baltic Sea

    Författare :Tomas Didrikas; Sture Hansson; Thomas Mehner; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Pelagic; fish; hydroacoustic; distribution; activity; Baltic; Biology; Biologi;

    Sammanfattning : Fisheries agencies around the Baltic Sea use hydroacoustics to assess stock sizes of herring and sprat. These assessments rely on the assumption that the acoustic properties of Baltic clupeids are the same as North Sea herring. LÄS MER

  4. 3. Direct and indirect effects of fish predation and excretion in aquatic food webs

    Författare :José Luiz Attayde; Biologiska institutionen; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; marine biology; Hydrobiology; zooplankton; resilience; predation; phytoplankton; nutrient enrichment; nutrient recycling; interaction strength; herbivory; food webs; food chain; excretion; fish; detritus; detritivory; aquatic ecology; limnology; Marinbiologi; limnologi; akvatisk ekologi; Ecology; Ekologi;

    Sammanfattning : The aim of this thesis was to elucidate the mechanisms by which planktivorous fish can affect planktonic communities in lakes and how they may affect benthic communities through their effects on planktonic communities. In a laboratory experiment, nutrients released by fish increased algal biomass and altered phytoplankton community structure, suggesting that fish can affect phytoplankton by directly releasing nutrients. LÄS MER

  5. 4. Local and global contaminants in Swedish waters : studies on PCBs, DDTs, 4,5,6-trichloroguaiacol and their transformation products in fish and sediments

    Författare :Maria Söderström; Åke Bergman; Bert van Bavel; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; PCB; DDT; HCB; trichloroguaiacol; transformation products; dimerisation; bromination; environmental pollutants; eutrophication; lakes; fresh water; baltic sea; monitoring; sediments; fish; phytoplankton; PCB; DDT; HCB; triklorguajakol; omvandlingsprodukter; dimerisering; bromering; miljöföroreningar; eutrofiering; sjöar; sötvatten; östersjön; miljöövervakning; sediment; fisk; fytoplankton; miljökemi; Environmental Chemistry;

    Sammanfattning : This thesis is focused on studies on the environmental fate and methodological improvements for determination of the global contaminants, PCBs and DDTs, and locally discharged phenolics, e.g. 4,5,6-trichloroguaiacol (4,5,6-TCG), and their transformation products. LÄS MER

  7. 5. Temporal relationships between fish-eating birds and their prey in a north Swedish river

    Författare :Kjell Sjöberg; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Seasonal and diel activity; food consumption; predator-prey relationships; fish-eating birds; anadromous fish; Mergus merganser; M. serrator; Sterna spp.; Larus spp.; Lampetra fluviatilis; Gasterosteus aculeatus;

    Sammanfattning : The seasonal and diel feeding habits of the goosander, Mergus merganser, the red-breasted merganser, M. serrator, gulls (Larus canus, L. argentatus and L. fuscusj and terns, Sterna hirundo/paradisaea were studied at 64V05'N. LÄS MER