ISSN:
1573-5125
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract In 1987, the Bleiswijkse Zoom, a small, shallow lake in The Netherlands, was divided into two compartments to investigate the possible use of biomanipulation as a tool for restoring the water quality of hypertrophic lakes. The density of the fish stock before restoration was about 650 kg.ha−1, composed mainly of bream, white bream and carp. Pikeperch was the main fish predator in the lake. In April, 1987, in one compartment (Galgje) all planktivorous bream and white bream and about 85% of the benthivorous bream and carp were removed. Advanced pikeperch fry were introduced as predator during the transient period. The other compartment (Zeeltje) was used as a reference. Removal of the fish in Galgje resulted in low concentrations of chlorophyll-a, total phosphorus, nitrogen and suspended solids. The absence of bottom-stirring activity by benthivorous fish and the low chlorophyll-a concentrations led to an increase in the Secchi disk transparency from 20 to 110 cm. Within two months after removal of the fish, macrophytes, mainly Characeae, became abundant. Until July the high density of large zooplankton species caused low algal biomass. From June onwards, the zooplankton densities decreased, but the algal concentrations remained low. This is probably because of nutrient limitation or depression of algal growth by macrophytes or both. Compared with the non-treated compartment the number of fish species in the treated compartment was higher. Perch, rudd and roach, i.e. the species associated with aquatic vegetation, were found in the samples. The survival of the O+ pikeperch was poor. The pikeperch could not prevent the growth of young cyprinids. Within two months after the removal of the fish a habitat for northern pike was created.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02286426
