Three years of experience in biomanipulating a small eutrophic lake: Lago di Candia (Northern Italy) |
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Authors: | Giussani Gianluigi de Bernardi Riccardo Ruffoni Teresa |
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Institution: | (1) C.N.R. Istituto Italiano di Idrobiologia, 28048 Verbania Pallanza, Italy |
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Abstract: | Results obtained from a step by step approach to the biomanipulation of a natural lacustrine environment (Lago di Candia,
Northern Italy) are presented. Since the diversion of the municipal sewage of the small town of Candia, runoff and precipitation
have been the sole contributors of nutrient to the lake. Fish population is mainly characterized by rudd (Scardinius erythrophthalmus) overstocking and by a low density of large-mouth-bass (Micropterus salmoides) and pike (Esox lucius). During 1986 about 12t of rudd (1–2 year old) were removed from the lake. Considering 1986 as ‘control year’, average Secchi disc transparency improved
from 2.3 m in 1986 to 3.3 m in 1988; phytoplankton biovolume decreased from 114 to 58 mm3 l−1 but zooplankton biovolume increased from 8 to 11.5 mm3 l−1. The results achieved show that a grodual biomanipulation treatment can have a satisfactory outcome, and has the advantage
of not producing catastrophic situations either in the biotic or in the abiotic compartments of the lake. |
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Keywords: | biomanipulation eutrophication fish stock lake recovery |
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