Structuring effect of submerged macrophytes on trophic relationships and distribution of fish in deep lakes (MacFish)
Project No. 7F14316
Applicant: RNDr. Jiří Peterka, Ph.D., Karl Oysten Gjelland, Ph.D.
Financial support: Czech-Norwegian Research Programme
Predation by fish is the primary top-down structuring force in aquatic ecosystems, and a change in predator-prey interactions involving fish may cause a change in the strength of trophic cascades and finally result in ecosystem shifts. Submerged macrophytes play an important role beyond that of primary production, as they provide increased structural complexity and niche potentials for fish. However, most of the scientific attention on habitat use in fish and the influence of macrophytes have been given to small and shallow lakes, where the vegetated areas are well-developed and the availability of a large deep water refugium is absent or limited. Our goal 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, we will contrast two newly formed deep lakes of similar size and colonization history, but one with and the other without submerged macrophytes. We will use the latest developments in high-resolution positioning telemetry to assess individual habitat use and activity patterns in the different species of the multispecies assemblages in the two lakes. This will be combined with other sampling techniques, such as echosounding, acoustic cameras, video cameras, electrofishing, trawling and gillnetting, with an emphasis on the non-lethal methods and covering all ontogenetic stages from fish larvae to mature adults. Individual trophic position will be assessed by diet studies and stable isotope analyses. We will use the resulting data to study intra- and interspecific overlap in habitat and trophic niche use, as well as activity patterns with high spatiotemporal resolution. Combined with consumption estimates in piscivorous predator fishes and life-history characteristics such as growth and age at maturation in prey fish, a comprehensive and detailed insight into the effect of submerged macrophytes on the fish community structures and dynamics will be reached. The project will provide novel basic research results that will have important relevance for the management and restoration of water bodies, and it will strengthen the cooperation and knowledge transfer between Czech and Norwegian aquatic ecosystem research.