Description
Submerged macrophytes play an important role beyond that of primary production, as they provide increased structural complexity and niche potentials for fish. Goal of the project is to gain a detailed understanding of the structuring effect the submerged macrophytes have on fish communities in deep lakes. In order to achieve this, two newly formed deep lakes of similar size and colonization history, but one with and the other without submerged macrophytes, will be contrasted. The latest developments in high-resolution positioning telemetry together with other advanced sampling methods will be used to assess individual habitat use and activity patterns in the different species of the multispecies assemblages in the two lakes. Individual trophic position will be assessed by diet studies and stable isotope analyses. Resulting data will be used to study intra- and interspecific overlap in habitat and trophic niche use, as well as activity patterns with high spatiotemporal resolution.
Summary of project results
The project objective was to gain a detailed understanding of the structuring effect the submerged macrophytes have on fish communities in deep lakes. In order to achieve this, two newly formed deep lakes of similar size and colonization history was contrasted, one with and the other without a well-developed community of submerged macrophytes. In order to achieve this, a plethora of different investigation methods were used, including diver observations, sampling of invertebrates, and sampling of fish with gillnets, trawling, longlines, electrofishing, echosounding and telemetry, with an emphasis on the non-lethal methods and covering all ontogenetic stages from fish larvae to mature adults. The macrophyte community was found to influence the fish communities and shape the trophic interactions in several ways. In generalist fishes with different ontogenetic trajectories, we demonstrated how the succession of macrophyte vegetation, via its effects on the physical and biological complexity of the littoral zone and on the availability of small prey fish and zooplankton, can strongly influence individual niche variation, and hence the overall foodweb structures in lake ecosystems. Among the fish predators, both pike and wels were found to have a larger home range in the macrophyte-poor lake as compared to the macrophyte-rich lake. The difference was strongest in pike, which showed a clear reduction in activity as macrophytes developed in the macrophyte-poor lake, as well as an activity increase as macrophytes became reduced in the macrophyte-poor lake. This consistency in pike behaviour in the between lake contrast and within lake seasonal change provide strong evidence for the influence of the macrophyte community on pike habitat use and activity.
Summary of bilateral results
The main objective of the project was to significantly contribute to the quantity and quality of our basic knowledge of processes structuring aquatic communities in deep lakes where the effect of macrophytes on the fish community structure and trophic relationships and habitat use has not been studied sufficiently so far. Impacted articles (Jimp ), book chapters (C), summarizing research reports (Vsouhrn), oral and poster presentations on scientific conferences and for broad public, popularizational articles. Institute of hydrobiology (IH) of the BC CAS conducts research of biotic interrelations and their interactions with abiotic factors in lentic water bodies, especially man-made reservoirs and natural lakes. The structure of the institute enables studies of the interrelations within the trophic food chains using both principal approaches: bottom-up (from chemistry to fish biology) and top-down (from fish biology to chemistry). NINA has a strong tradition in combining field observations with ecological theory through modelling approaches, involving studies of individual habitat requirements, use, and movement. Main benefit was the exchange and adoption of methodological approaches not used so far. The strengthened cooperation and knowledge transfer between Czech and Norwegian aquatic ecosystem research institutions. Involvement of doctoral students and postdoctoral fellows in international project had significant positive effect on young scientist carrier and the transfer of knowledge on 3D acoustic positioning system and data management and processing from the Norwegian to the Czech partner and consequent continuing cooperation and research networking. The partnership has created new and solid scientific collaboration, which will last far beyond the project period. Cooperation has also been established between the partners in other projects, and new joint project applications will arise. The project provided not only novel basic research results but the outcomes have important relevance for the management and restoration of abandoned mining sites.