The aim of this study was to determine the differences of freshwater pearl mussels (Margaritifera margaritifera) originated from two geographically isolated areas according to morphological parameters and the age of dead freshwater pearl mussel Data were collected from four localities, i. e. from the two areas (Šumava: Blanice, Zlatý potok and Aš area: Bystřina and Rokytnice). The average length of shells was 95.8 mm, thickness 27.9 mm, height 43.4 mm. The ligament was eroded from 57 % and index (ration between thickness and length x 50) was on average 32 %. Thickness of the shells and the percentage of eroded ligament differed between the two areas. Both of these parameters were higher in Aš area. Other morphological parameters (length and height of the shells and the above mentioned index) were similar in both areas. Assessment of age according to the growth lines in the ligament was significantly higher than the evaluation using growth lines on the surface of the shells. Mean age of freshwater pearl mussels determined using growth lines in the ligament was 36 years old and on the surface of the shells was 30 years old. Age according to the growth lines in the ligament better correlated with the length of the shell than percentage of eroded ligament. Age of dead freshwater pearl mussel was comparable in both areas, however differed between localities. Rokytnice proved to be the most suitable habitat for freshwater pearl mussels according to the age estimation.

Unionida musslor (stormusslor) är en djurgrupp som kan ha positiv påverkan på ekosystemfunktioner i vattendrag och ökar den biologiska mångfalden. Musslorna absorberar föda genom filtrering av vattenmassor, vilket genererar en bättre vattenkvalitet och ger mat till andra bottendjur. Syftet med denna studie var att undersöka en av våra svenska stormusslor flodpärlmusslan (Margaritifera margaritifera), och om det fanns något samband mellan musselbankar och bottenfauna. Provtagning av bottenfauna skedde i Vasslabäcken, Örebro län. 54 prover togs totalt och 27 av dem togs vid musselbankar medan resterande 27 var kontroll utanför musselbankar. Studien visade ingen signifikant skillnad i den totala bottenfaunans täthet i musselbankar jämfört med kontrollområden utanför musselbankar. Däremot fanns en signifikant högre täthet av nattsländor i kontrollerna än i musselbankarna, medan det inte fanns några skillnader i täthet mellan kontroller och musselbankar för några andra djurordningar. Det fanns även fler ordningar utanför musselbankar än i musselbankar, men antalet individer var så få att inga långtgående slutsatser kan dras. För att vidare undersöka musslors påverkan på flora och fauna kan man undersöka fler år och säsonger under året, samt använda sig av en mer experimentell design. / Unionidea mussels (large mussels) are a group of animals that can have a positive impact on ecosystem functions in watercourses and increase biodiversity. The mussels absorb food by filtering water masses, which generates a better water quality and provides food for other benthic animals. The purpose of this study was to investigate one of our swedish large mussels the freshwater pearl mussel (Margaritifera margaritifera), and whether there was any connection between musselbanks and benthic fauna. Sampling of benthic fauna took place in Vasslabäcken, Örebro region. A total of 54 samples were taken and 27 of them were taken at musselbanks while the remaining 27 were controls outside musselbanks. The study showed no significant difference in the density of the total benthic fauna in musselbanks compared with control areas outside musselbanks. On the other hand, there was a significantly higher density of moths in the controls than in the musselbanks, while there were no differences in density between controls and musselbanks for any other animal orders. There were also more schemes outside musselbanks than in musselbanks, but the number of individuals was so small that no far-reaching conclusions can be drawn. To further investigate the impact of mussels on flora and fauna, you can investigate more years and seasons during the year, and use a more experimental design.