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Year-to-year
stability of aggregations of Viviparus
viviparus (Linnaeus 1758) in littoral zone of lowland, rheophilic
reservoir (central Poland) |
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Beata
Jakubik |
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Department
of Ecology and Environmental Protection, University of Podlasie, 08-110
Siedlce, Poland, e-mail:ekologia@ap.siedlce.pl |
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Abstract: The aggregations of V. viviparus were observed in the littoral of Zegrzyński
Reservoir (Central Poland), and in the outfalls of its tributaries. They were
present over five years of studies (1990–1994), at the same sites. The
densities of snails in the aggregations differed among the sites (from over
800 ind.·m-2 to 500 ind.·m-2 in the reservoir itself),
and showed seasonal changes with maximum in summer, and minimum in spring and
fall. Swarming of the snails was related to the environmental changes and
biology of this species. Tendency to form bigger snail conglomerations in the
mouth sections of the rivers results from continuous inflow of organic matter
being food supply for these organisms. |
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Key words: lowland
reservoir, V. viviparus,
aggregation, river |