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  • 1995-1999  (4)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Diel and seasonal distribution of perch in Lake Constance: a hydroacoustic study and in situ observations (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 49 (1996), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A near-shore belt 50 km in length was surveyed parallel to the shoreline of Lake Constance, central Europe, with a single-beam echosounder five times between July 1993 and February 1994. The species and age composition of fish in the survey area was investigated by gillnet fishing and SCUBA-diving. In summer, the horizontal distribution of perch was patchy. Population density declined from east to west, and highest densities occurred in one shallow bay and close to ports and jetties at steeper shores. During daytime, perch stayed in the sublittoral zone between 3 and 15 m depth and between 2 and 6 m above the thermocline. Within this layer age classes were separated spatially: the relative number of young-of-the-year perch declined with depth whereas the relative number of adult perch (2+ and older) increased with depth. At dusk the fish migrated to the littoral zone, where they spent the night resting on the bottom. In winter, under almost homothermal conditions, perch of all ages were located between the 35 and 70 m depth contours, where they performed pronounced diel vertical migrations. They rested on, or close to, the bottom during daytime and ascended up to 20 m below the surface at night. During this season, horizontal distribution of perch was much more homogeneous than in summer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1996.tb00001.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    First-year overwinter mortality in Eurasian perch (Perca fluviatilis L.) Results from a field study and a simulation experiment (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Ecology of freshwater fish 8 (1999), S. 0 
    Details
    ISSN: 1600-0633
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract– The importance of overwinter mortality of 0+ perch (Perca fluviatilis L.) in central European lakes was estimated using a stochastic simulation model. The probability of overwinter mortality of a perch cohort was calculated by using a model developed for yellow perch (P. flavescens Mitchill). Winter duration from a long-term data set and the length of perch at the end of the first year from five lakes were used as input data. After 1000 simulation runs, the total extinction of a cohort in the lakes studied was never predicted. Mortality rates of more than 0.5 were only predicted in two of the five lakes, and rates of more than 0.3 in these two lakes were predicted in approximately 10% of all cases. For two consecutive winters differing in duration, the length-frequency distributions of 0+ perch in the autumn and following spring were compared by a graphical method. No significant size-dependent mortality of smaller individuals could be detected in any of the populations studied. Simulated spring length-frequencies were derived from observed autumn length distributions by the same model that was used for the stochastic simulation. These simulated and the empirical spring length-frequency distributions were not identical. The differences between the two distributions were attributed to growth, which occurred between the sampling dates. The results from the simulation and the analysis of the empirical data suggest that high overwinter mortality caused by starvation is rare in central European lakes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-0633.1999.tb00059.x
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Fish species richness in lakes of the northeastern lowlands in Germany (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Ecology of freshwater fish 4 (1995), S. 0 
    Details
    ISSN: 1600-0633
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Fish species richness was assessed by electrofishing and gillnetting in 16 lakes of the northeastern lowland in Germany (the Schorfheide biosphere reserve). The lakes range from 0.03 to 10.55 km2 and support between 5 and 14 fish species. Species richness is significantly correlated with lake area in an exponential and a power model. Richness is also correlated with shoreline development and total dissolved solids. This supports the hypothesis that larger areas contain more species within a taxonomic group due to increased habitat diversity. The slope of the species-area curve is low compared with most other studies of fish species richness in lakes, and the intercept value is high. This is interpreted as the result of high habitat and food diversity, lack of stress from abiotic factors, and the small regional species pool from which these lakes can be colonized. Two species inventories, one from the beginning of this century and one from the 1950s, are available for comparison. Average species richness did not change during the last decades. Species turnover rates were not related to the degree of anthropogenic eutrophication or to the intensity of fishery exploitation in these lakes. On the species level, however, one effect of accelerated eutrophication is apparent, the disappearance of 4 bottom-living species from one to 6 of the study lakes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-0633.1995.tb00118.x
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Does water calcium content influence the distinctness of daily growth increments in the otoliths of larval whitefish (Coregonus lavaretus L.)? (1999)
    Oxford, UK : Blackwell Science, Ltd
    Journal of applied ichthyology 15 (1999), S. 0 
    Details
    ISSN: 1439-0426
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: In larval and juvenile whitefish (Coregonus lavaretus L.) from Lake Constance, Germany, the otolith increments are deposited daily, whereas daily deposition could not be confirmed in larval whitefish from Lake Pyhäselkä, Finland. The calcium concentration in Lake Constance is high (around 1.3 m m), while calcium deficiency is typical for Finnish lakes (around 0.15 m m). Therefore, the hypothesis that the distinctness of daily otolith increments in whitefish is related to water calcium content was tested by rearing three groups of Lake Constance whitefish in water of 0.2, 1.3 and 4.7 m m Ca. The eggs were incubated in lake water (1.3 m m Ca), and the larvae were acclimated to the experimental calcium concentrations on the day of hatching. After 39 days of ad libitum-feeding with Artemia nauplii, the three groups did not differ significantly in total length, wet and dry weight, and otolith length and width. The daily increments were easily recognizable, and contrast between dark (D)- and light (L)-zones was the same in the fish of all test groups. For the experimental set-up of this study, and particularly the range of calcium concentrations tested, the hypothesis that water calcium content influences the distinctness of daily otolith increments was rejected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1439-0426.1999.00124.x
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    Paper (German National Licenses)
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