Effects of environmental factors, especially temperature, on the population dynamics of pikeperch (Stizostedion lucioperca (L.))

    Tutkimustuotos: OpinnäyteVäitöskirja


    The effects of environmental factors on the population dynamics of pikeperch (Stizostedion lucioperca (L.)) were analysed in the coastal areas of the northern Baltic Sea and in three lakes. The thesis is a summary from seven articles based on long-term data collected mainly by different Finnish and Estonian institutes. The studied abiotic factors were air and water temperature, water
    level and salinity, secchi disk depth, wind velocity and distribution, and the duration of winter. The main studied biotic factors were length and abundance at age 0, and year-class strength and yields during subadult and adult stages.

    The study revealed that the most important environmental factor affecting the population dynamics of pikeperch was temperature. Water temperature had positive effects on annual abundances, growth, year-class strengths and yields. Mortality during the first winter was shown to be dependent on size, but the ranks of year-class strengths were already established by the end of July during the first growing season. The results further suggest that the size-dependent winter mortality should be higher after cold than warm summers. The strong dependence on temperature is also seen in similar year-class strength variations over different pikeperch populations. Strong year-classes were born
    during warm summers and weak ones during cold summers. Other studied environmental factors had little or no effects on the population dynamics. This was probably due to the fact that the interannual variations in these factors were within suitable levels and hence had no clear effects on year-class strengths.

    Pikeperch, as a warm water species, seems to benefit from predicted climate warming based on the several positive effects of temperature on population dynamics. The results suggest stronger yearclasses and higher yields for pikeperch in a warmer climate. However, based on current knowledge, it is not possible to evaluate the potential changes in interactions among abiotic and biotic factors which might occur and which could cause unexpected surprises in the future.
    TilaJulkaistu - 2001
    OKM-julkaisutyyppiG5 Tohtorinväitöskirja (artikkeli)


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