Repeated Fish Removal to Restore Lakes: Case Study of Lake Væng, Denmark—Two Biomanipulations during 30 Years of Monitoring

Abstract

Biomanipulation by fish removal has been used in many shallow lakes as a method to improve lake water quality. Here, we present and analyse 30 years of chemical and biological data from the shallow and 16 ha large Lake Vaeng, Denmark, which has been biomanipulated twice with a 20-year interval by removing roach (Rutilus rutilus) and bream (Abramis brama). After both biomanipulations, Lake Vaeng shifted from a turbid, phytoplankton-dominated state to a clear, water macrophyte-dominated state. Chlorophyll a was reduced from 60-80 µg·L −1 to 10-30 µg·L −1 and the coverage of submerged macrophytes, dominated by Elodea canadensis, increased from <0.1% to 70%-80%. Mean summer total phosphorus was reduced from about 0.12 to 0.07 mg·L −1 and total nitrogen decreased from 1.0 to 0.4 mg·L −1 . On a seasonal scale, phosphorus and chlorophyll concentrations changed from a summer maximum during turbid conditions to a winter maximum under clear conditions. The future of Lake Vaeng is uncertain and a relatively high phosphorus loading via the groundwater, and the accumulation of a mobile P pool in the sediment make it likely that the lake eventually will return to turbid conditions. Repeated fish removals might be a relevant management strategy to apply in shallow lakes with a relatively high external nutrient loading.

Lake Restoration and Management in a Climate Change Perspective: An Introduction

“…Repeated treatment has therefore been suggested [7]. In an article in this special issue [21], an analysis is presented of 30 years of chemical and biological data on shallow 16 ha Danish Lake Vaeng that has been biomanipulated twice with a 20-year interval by removing coarse fish, the second time due to unsatisfactory long-term results. After both biomanipulations, the lake shifted from a turbid, phytoplankton-dominated state to a clear water macrophyte-dominated state.…”

Search for Environmental Causation of the Cladoceran Dynamics in Lake Kinneret, Israel

“…Monthly averages of Small (left 3 panels) and Large (right 3 panels) organisms of Diaphanosoma (upper 2 panels), Bosmina (middle 2 panels) and Ceriodaphnia (2 lower panels) densities (No./l) in Lake Kinneret (1975Kinneret ( -1985. The fish removal by fishery management was documented by Sondergaard et al [22]. This kind of management, namely, Biomanipulation, has been used in many shallow lakes aimed at water quality improvement.…”

Restoration of Shallow Lakes in Subtropical and Tropical China: Response of Nutrients and Water Clarity to Biomanipulation by Fish Removal and Submerged Plant Transplantation

“…This provides further evidence [3] of the usefulness of biomanipulation as a restoration technique in warm shallow eutrophic lakes after a sufficiently high external loading reduction. However, in temperate lakes, repeated fish removal is suggested to obtain a longer-lasting clear water state [3,50], and such repeated removal may also be recommended for warm shallow lakes. The warm lakes are dominated by omnivorous fish in both the turbid and the clear water states [32], and it has been shown that adult omnivores feed mainly on submerged macrophytes in the restored part of Huizhou West Lake [37] as well as in Lake Wuli [38], and high abundances of these species could lead to a return of the turbid state.…”