The effects of habitat complexity and infections from freshwater pearl mussel larvae on brown trout interactions

Many species are today threatened by extinction. In streams and rivers, the historical clearing of obstacles in favour of transportation of floating timber has led to a decrease in the important habitat complexity. The larvae of freshwater pearl mussel (Margaitifera margaritifera) lives as a parasite on the gills of brown trout (Salmo trutta)wich effects the host negatively. In this study the effects of the activity, the amount of prey captured and the amount of initiated interaction with other trouts in different habitat complexity and different grade of infection from glochidia was investigated. The behaviour of brown trout was studies in the laboratory at Karlstads university in 2015. Analyses from data collected in laboratory studies at Karlstad University showed that there was no significant difference in activity or the amount of food captured between fish in complex and homogeneous habitats with high or low infection. In the case of initiated interactions there was a significantly higher rate of initiated interactions in homogeneous habitats than in complex habitats. The understanding of how the host is affected by parasites and even a changing habitat is important to be able to protect sensitive species with a parasitic lifecycle.