|The influence of biomanipulations (fish removal) on the structure of lake foodwebs, case studies using the LakeWeb-model|
Håkanson, L.; Boulion, V.V.; Ostapenia, A.P. (2003). The influence of biomanipulations (fish removal) on the structure of lake foodwebs, case studies using the LakeWeb-model. Aquat. Ecol. 37(1): 87-99
In: Aquatic Ecology. Springer: Dordrecht; London; Boston. ISSN 1386-2588, more
Benthos; Biomanipulation; Environmental factors; Fish; Functional morphology; Lakes; Models; Phytoplankton; Zooplankton; Belarus [Marine Regions]; Sweden [Marine Regions]
|Authors|| || Top |
- Håkanson, L., correspondent
- Boulion, V.V.
- Ostapenia, A.P.
This paper presents results on how intensive fishing (fish removal) is likely to influence the structure of lake foodwebs. The work is based on a comprehensive dynamic lake ecosystem model, LakeWeb, which accounts for production, biomasses, predation and abiotic/biotic interactions of nine key functional groups of organisms: phytoplankton, bacterioplankton, two types of zooplankton (herbivorous and predatory), two types of fish (prey and predatory), zoobenthos, macrophytes and benthic algae. The model uses ordinary differential equations, the ecosystem scale and gives seasonal variations (the calculation time is 1 week). It is designed to account for all fundamental abiotic/biotic interactions and feedbacks for lakes in general for the nine target groups. The LakeWeb-model has been calibrated and critically tested using empirical data and regressions based on data from many lakes. It has been shown that the model can closely capture typical functional and structural patterns in lakes, which should give credibility to the results presented in this work. Obtaining such results using traditional methods, i.e., extensive field studies in one or a few lakes, would be very demanding (in terms of money, persons involved and time). In this paper, results are presented for two lakes, one Swedish and one Belarussian. The intensive fishing operations carried out in Lake Blacksåstjärn, Sweden, to reduce Hg-concentrations in fish did not succeed. A typical cost of an intensive fishing is about 10,000-30,000 USD per lake of this size (≤ 0.25 km2). The costs to remove fish would be about 40-120 USD per kg ww fish removed! Intensive fishing simulated for Lake Batorino, Belarus, to reduce the fish biomass will likely increase the prey fish biomass as long as the predation pressure on prey fish is lower than during the prefishing stage. The biomass of predatory fish will recover only slowly. However, this operation is not likely to succeed in lowering the algal volume in lakes with a high biomass of predatory zooplankton. This is easy to state qualitatively and the LakeWeb-model offers a practically useful tool to quantify such changes and identify lakes where biomanipulations are likely to fail or succeed.