PL
Perłoródka rzeczna, nazywana też skójką perłorodną, to duży małż słodkowodny, charakteryzujący się szczególną zdolnością samoistnego tworzenia pereł – z tego względu od wieków niemiłosiernie eksploatowany, ale i otaczany ochroną prawa. Na obszarze dzisiejszej Rzeczpospolitej udokumentowano jej występowanie jedynie w Sudetach, gdzie pomimo prób ochrony prawnej wymarła prawdopodobnie na początku XX w. Czy możliwe jest odtworzenie występowania tego gatunku w Polsce ?
EN
The freshwater pearl mussel is a typical flag species, which attracts public interest in nature conservation. Its flag role is related to ability to create pearls. We have reviewed historical information on the pearl mussel exploitation and its potential influence on the persistence of the species. The Sudety Mts with the upper sections of the Bóbr, Nysa Łużycka and Kwisa rivers abounding in pearl mussels had become the well known area of pearl fishing since the 17th century. The first evidence of overfishing, recorded in the first half of the 18th century, was a decree issued in 1729 by August II Mocny (Friedrich August I), king of Poland and Saxon elector, forbidding pearl fishing due to the low population of the pearl mussel. Kacper Ludwig Trebluth, the last person granted by king of Poland and Saxon elector, August III Sas (Friedrich August II) a licence for pearl fishing (in the Sudety Mts. in the period of 1753–1769), could not earn his livelihood from this activity. The last records of pearl mussels shoals were, provided by local naturalists from the upper Kwisa river at the end of the 19th century . It is difficult to identify factors which caused the species decline. It is obvious that similarly as in other countries of Europe, the species decline is associated with the intensive development of agriculture and industry, which caused major changes in the landscape. One factor seems to be more important than previously believed: intense river and streams regulation (artificial stone-lined channels). The development of watermills and local industry, and the intense development of human settlements forced the regulation of any stream; in addition, water quality decreased due to agriculture (deforestation) and industrial sewage. It is rather improbable that muskrat Ondatra zibethicus could influence the pearl mussel population because that species was purposefully released from captivity in Czech (1905) after the pearl mussel had become extinct. In Poland no intensive search of freshwater pearl mussels was carried out. The species has been regarded as extinct since 1960. The inventory of water courses in the Sudety Mts., done in 2006–2007, did not show the species presence, except for a few well preserved shells found in Koci Potok (Fig. 2). It may indicate that a relic population can still live in this stream or that some subfossil remnants have been excavated by the stream. The inventory has also shown that the number of water courses which could meet the habitat requirements of pearl mussels is very low. On the other hand, land abandonment has caused spontaneous restoration of some streams in Sudety Mts. The general improvement of environmental conditions in the whole region, especially in terms of water quality, as well as the plans of indigenous salmonid fish reintroduction create habitat conditions appropriate for the freshwater pearl mussel. A chance of restoring or reintroducing the species has been assessed, taking into account the interest of local communities.