Evaluation of potential host-fishes for Unio crassus needs information of glochidia load and survival on fish gills. Therefore, many fish individuals of different species, hatched and infested in the aquaria room at Lunds University (see previous blog text), were sacrificed and measured in weight and length on a Saturday afternoon/evening. Labeling the fishes was a very important procedure since each individual will be correlated to this data when checking for glochidia infestation rates using a stereomicroscope. Last week a few fish individuals could already be checked for glochidia infestation and many pictures could be taken. On some individuals an immune reaction was visible on the gills. On other individuals successful infestations was indicated by fish-tissue which had been growing over mussel glochidia. This information helps us now to choose fish species for the next UC4LIFE action: re-introduction of U. crassus in the streams Klingavälsån and Fyleån. For this experiment, let’s hope that we still can find gravid mussels in the steams of Skåne!