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Institut für Wasser- und Umweltsystemmodellierung - IWS



"Colmation - Simulation of interstitial habitat conditions during the incubation phase of gravel-spawning fish "

The relevance of colmation processes for interstitial habitats, demanded by aquatic species that live or have life-cycles associated with the sediment characteristics of river beds, is well-known and many studies use colmation as an important habitat describing variable. However, the applicability of colmation for modelling pruposes is limited due to two facts. On the one hand, there is no unique definition of colmation and on the other hand the dynamics of colmation processes are not yet predictable. In scientific literature different terms like embeddedness, colmation and clogging are used and in most studies the focus is set on purely sedimentary colmation neglecting important biogeochemical processes that affect the interstitial habitat conditions. Further, all assessment techniques (measuring, mapping) only cover the current state of colmation in a river – a temporal snapshot – and neglect the dynamic processes that are involved in the evolution of colmated river be ds. The objective of this article is to present a habitat-based modelling approach which simulates an interstitial habitat suitability (IHS) considering dynamically varying interstitial habitat conditions during the incubation phase of gravel-spawning fish. Therefore, three key factors describing the interstitial habitat are linked to the habitat requirements of different developmental stages during the incubation period (eyed-egg, hatching, larvae) via a multivariate fuzzy-approach: the permeability of the gravel river bed, the interstitial temperature, and the hyporheic respiration. The multivariate fuzzy-approach combined with a numerical sediment-transport model allows for a dynamic consideration of the aforementioned habitat variables and thus for a dynamic development of interstitial habitat conditions. The modelling approach provides results in form of habitat suitability maps and habitat suitability time-series over the entire incubation period which allows for an identifica tion of abiotic bottlenecks during incubational development.