Research Projects within the Institute's Research ProgramTopics in basic research1. Regulation of fish diversity in running waters Co-ordinator: Prof. Dr. F. Kirschbaum Running waters are characterised by stochastic hydrological events leading to unpredictable availability, alteration and destruction of habitats. On the basis of our previous data on fish recruitment phenomena we postulate that abiotic key factors structure fish assemblages in large rivers. Running waters in addition are inhabited by biocoenoses of high diversity aligned along classical ecological gradients. Accordingly, we will study life history strategies of two closely related species of the genus Cottus occurring in a parapatric pattern within the Lower Rhine drainage. Both species strongly diverge in their potential to colonize sub-regions within an ecological continuum. For comparison, we investigate the sympatric speciation of the African mormyrid genus Campylomormyrus from the Congo River. In the River Sieg a long-term study focuses on the determination of species-specific recruitment and fish community structure by climatic factors, inclusive of ”global warming”. A central obligation of our society is the long-term preservation of ecosystems and genetic diversity. Therefore, as part of a restoration project of two Atlantic sturgeons native to Germany, Acipenser sturio and A. oxyrinchus, we are developing ex situ brood stocks. First findings based on molecular genetics indicated a sympatric occurrence of both species in the Baltic Sea over several hundred years, which has significant implications for restoration strategies. The brood stock development is still in an experimental stage due to a lack of knowledge concerning growth and feeding, in particular of A. sturio. 2. Ecological factors in speciation of fishes Co-ordinator: PD Dr. T. Mehner In previous years, the adaptive value of fine-scaled distribution patterns of lake fish and their consequences for other trophic levels were estimated. Furthermore, we have established respirometry, enzyme activity measurements and individual-based modelling to compare energy allocation strategies in freshwater fish belonging to different temperature preference guilds such as roach and burbot. We can now utilise these findings and techniques to focus on the contribution of habitat choice, migration patterns, and energy allocation strategies to fish speciation. Ecological specialisation of sub-populations is a potentially major process leading to sympatric speciation. If these adaptations are translated into heritable traits, restricted interbreeding and thus genetic incompatibility may arise. However, field-based evidence for sympatric speciations based on ecological specialisation is rare. As model systems, we use the two species pairs of ciscoes (Coregonus spp.) in Lakes Stechlin and Breiter Luzin which show significant, albeit low, genetic as well as morphological differences indicating a sympatric origin. First analyses found ecological differences in growth trajectories, life histories, migration patterns and diet choice between the two species within each pair. Furthermore, both pairs differ with respect to their spawning time, thus an ongoing complete genetic separation and physiological differentiation is most likely. Our work is guided by the hypothesis, that differential ecological adaptation of the cisco species pairs in both lakes is a main driving force in sympatric speciation. Topics in applied research3. Scientific basics for fisheries management in aquatic ecosystems Co-ordinator: Dr. R. Arlinghaus Because of the obvious differences between aquaculture and capture fisheries systems, this research project specifically deals with fishing activities in natural and anthropogenically created surface waters. Previous research addressed (1) reconciliation of traditional inland fisheries management with sustainability; (2) development of an integrated guideline to couple water quality and fisheries management by biomanipulation; (3) fisheries management in Lake Stechlin, with emphasis on the genetics of ciscoes (Coregonus spp.); and (4) analysis of the socio-economic importance of recreational angling in Germany. Our in-depth evaluation of recreational fisheries demonstrated the overwhelming dominance of this type of fishing within the German inland fisheries sector. Therefore, in the future we will focus on recreational fisheries and its management issues (e.g., stocking, specificities of fisheries management in urban water bodies including socio-economic aspects, ecological and evolutionary impacts of size and species selective exploitation patterns).
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