pondělí 25. ledna 2016

Monitoring the freshwater pearl mussels‘ population and their biotope

Freshwater pearl mussels in the Aš region have been taken care of for many years by Czech and German professionals. Together we have been trying to boost the aging population by juveniles, to support host fish and to improve the state of the biotope – the actual streams and their surroundings. At the same time it is necessary to check out the effectiveness of the measures taken, to make sure we are really helping the pearl mussels. That is why regular monitoring of the pearl mussels’ population and checks on the biotope state are being carried out. In 2015, pearl mussels were counted in Bystřina and special biotope quality test were undertaken.

The monitoring results show that in the last five years the population of freshwater pearl mussels has declined by one half. This progress is not surprising; it is caused mainly by a high age average of the population, where most individuals are close to the maximum age. But what was encouraging was the finding of juveniles coming from Saxon rearing which confirmed its efficiency. Therefore it is recommended to continue in semi-natural rearing which helps pearl mussels overcome the critical period.

The biological indication method was developed to check the quality of a biotope. Here, juvenile pearl mussels are placed into the stream in special panels and their mortality and growth are measured. Last year’s tests have shown lower mortality and bigger growth of pearl mussels in places where we take care of the biotope, e.g. by maintaining food brooks or meadow vegetation, than in other parts of the streams.

This website was created with the financial support of the EEA Grants 2009–2014 and the Ministry of the Environment of the Czech Republic. Responsibility for its contents fully lies with the NGO Ametyst - branch Karlovy Vary and the website may in no circumstances be considered to be the opinion of the donor or of the Ministry of the Environment of the Czech Republic.