The Status of Freshwater Pearl Mussel in the Czech Republic: Several
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Limnologica 50 (2015) 11–20 View metadata, citation and similar papers at core.ac.uk brought to you by CORE Contents lists available at ScienceDirect provided by Elsevier - Publisher Connector Limnologica jo urnal homepage: www.elsevier.com/locate/limno The status of freshwater pearl mussel in the Czech Republic: Several successfully rejuvenated populations but the absence of natural reproductionଝ a,b,∗,1 c,d,1 b e Ondrejˇ P. Simon , Ivana Vaníckovᡠ, Michal Bíly´ , Karel Douda , f g c Hana Patzenhauerová , Jaroslav Hruskaˇ , Alena Peltánová a T.G Masaryk Water Research Institute, Podbabská 30, CZ-16000 Prague 6, Czech Republic b Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamycká´ 129, CZ-16521 Prague 6, Czech Republic c Nature Conservation Agency (NCA CR), Kaplanova 1931/1, CZ-14800, Prague, Czech Republic d Biology Centre of the Academy of Sciences of the Czech Republic, Institute of Hydrobiology, Na Sádkách 7, CZ-37005 Ceskéˇ Budejovice,ˇ Czech Republic e Faculty of Agrobiology, Food and Natural Resources, Czech University of Life Science, Kamycká´ 129, CZ-16521 Prague 6, Czech Republic f Institute of Vertebrate Biology, Academy of Sciences of the Czech Republic, Kvetnᡠ8, CZ-603 65 Brno, Czech Republic g Miletínky 7, CZ-383 01 Ktis,ˇ Czech Republic a r t i c l e i n f o a b s t r a c t Article history: The freshwater pearl mussel was historically abundant in many streams and rivers in the Elbe, Oder, and Received 31 March 2014 Danube Basins in the Czech Republic, Central Europe. By the 21st century, the mussels had become extinct Received in revised form in the lower and middle altitudes, and current populations are only present near the upper limit of their 17 November 2014 natural range. The current population of this mussel is estimated to be only 1% of the historical abundance. Accepted 18 November 2014 The population decline was related to the negative impacts of pollution from industry, intense agriculture, Available online 24 November 2014 forestry, and sewage water. The freshwater pearl mussel habitat has also been impacted by watercourse regulations and has been fragmented by dams and weirs. All of these impacts have resulted in failure of Keywords: the reproductive cycle; the last significant cohort of juveniles settled approximately 30 – 40 years ago. Margaritifera margaritifera Therefore, this species is considered critically endangered, and an action plan was developed to conserve Action plan Unionidae the populations in the Czech Republic. Special measures were conducted between 1984 and 2005 to Conservation biology improve the age structure of elderly populations. Fish infected with millions of glochidia were released Long-term study in two locations, and over 53,000 captive-bred juveniles that were three to five years old were released in Rejuvenation seven locations. Only the latter approach resulted in a small number of subadults that gradually emerged from the substratum to the bottom surface, as confirmed by monitoring efforts. Despite simultaneous efforts to restore mussel habitat over the last 25 years, natural reproduction still does not occur in the Czech Republic. Therefore, complete restoration of oligotrophic streams is the key to the future presence and natural reproduction of freshwater pearl mussels in the Czech Republic. © 2014 The Authors. Published by Elsevier GmbH. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/). Introduction tifera) was historically an abundant species in oligotrophic streams, but it has been disappearing rapidly in recent decades. This species Freshwater species, particularly bivalve molluscs, are greatly has a complex life cycle that begins with a very brief planktonic threatened with extinction (Bauer and Wächtler, 2001; Strayer, phase in the form of microscopic glochidia, which is followed by 2006), and their protection requires a comprehensive approach a parasitic phase on the gills of salmonid fishes for nearly a year. (Geist, 2011). The freshwater pearl mussel (Margaritifera margari- The completion of metamorphosis is followed by a hidden phase in hyporheic zone. Finally, the young mussel emerges at the bot- tom surface and may live up to a century as a stable, sessile benthic filter-feeder consuming fine detritus (Bauer and Wächtler, 2001). ଝ This article is part of a special issue entitled “The current status and future chal- The complexity of the freshwater pearl mussel’s lifecycle makes lenges for the preservation and conservation of freshwater pearl mussel habitats”. ∗ it vulnerable to rapid anthropogenic changes that have affected Corresponding author at: T.G Masaryk Water Research Institute, Podbabská 30, freshwater ecosystems over the last two centuries. CZ-16000, Prague 6, Czech Republic. Tel.: +420 220197365. Currently, the freshwater pearl mussel is designated endan- E-mail address: [email protected] (O.P. Simon). 1 These authors contributed equally to this work. gered species based on European Union legislation and is protected http://dx.doi.org/10.1016/j.limno.2014.11.004 0075-9511/© 2014 The Authors. Published by Elsevier GmbH. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/). 12 O.P. Simon et al. / Limnologica 50 (2015) 11–20 within Natura 2000. According to the national law of the Czech initial results of the long-term attempts to augment the residual Republic, the species has been listed as critically endangered since populations. 1992 but has been under legal protection since 1913, when it was declared a year-round protected species and harvesting of wild Methods populations was banned. Mussels were allowed to be cultured for pearl production in artificial millraces. The last documented offi- The study area cial pearl hunt occurred in 1944 in the millrace of Otava River in Horazd’oviceˇ (Dyk, 1947; Dyk and Dyková, 1974). The conservation The study area is located on the southeast edge of the freshwa- of the freshwater pearl mussel in the Czech Republic was cov- ter pearl mussel range in Europe. The area includes the following ered by the nation’s general environmental protection legislation river catchments: the Vltava and Saale Basins of the upper Elbe announced in 1955. River, which drains into the North Sea; the Oder and Nisa Basins Despite their protection over several decades, the freshwater of the upper Oder River, which drains into the Baltic Sea; and the pearl mussel is retreating from its natural range across Europe Morava Basin of the Danube River, which drains into the Black (Araujo and Ramos, 2001; Popov and Ostrovsky, 2013). Generally, Sea. The original range of the freshwater pearl mussel is rela- the causes of declines have been eutrophication, river regulations tively sparsely settled and is characterised by a high percentage and changes in land use in catchments (Bauer, 1988; Hruska,ˇ 1999; of forested areas, with a current predominance of spruce monocul- Gumpinger et al., 2002; Geist, 2010). In the Czech Republic, the first tures. In the bedrock, crystalline rocks (granite, granodiorite, and documented massive die-out of freshwater pearl mussels occurred diorite) are dominant. via the construction of paper mills and other industrial enterprises The conservation of freshwater pearl mussels in the study area between 1850 and 1940 (Dyk, 1947). Subsequently, the discharge is managed by the governmental Nature Conservation Agency (NCA of untreated sewage water, the construction of dams, and the reg- CR) in the form of a national action plan. The action plan categorises ulation of stream canals had additional profound negative impacts localities with viable populations according to their current and on this species. Land use changes also occurred; for example, tra- predicted statuses (Supplement A). An ecosystem-oriented con- ditional farming on less productive land was gradually abandoned servation approach is used to reflect the complex processes in such that former fields and meadows returned to natural succes- oligotrophic waters that are key to freshwater pearl mussels’ sur- sion, and agriculture on more productive fields was intensified vival and reproduction. (Dyk, 1992; Hruska,ˇ 1991b). Forest diversity was modified when the proportion of spruce monocultures increased. The water course Analysis of available data on historic freshwater pearl mussel within the landscape was managed via the massive construction of occurrence drainage systems, which caused the physical destruction of many natural streams due to digging and elevated levels of erosion (NCA The data of the historical occurrence of freshwater pearl mus- CR, 2013). sels in Czech rivers and streams were summarised from various These cumulative effects had a significant impact on the tem- reports (Schubert, 1933; Nowak, 1936; Dyk, 1947; Podubsky´ perature regime, erosion patterns, and water chemistry, which and Stˇ edronskˇ y,´ 1955; Svatos,ˇ 1971; Dyk and Dyková, 1974; resulted in changes in the aquatic food webs of individual river Flasar, 1992). Historical occurrences obtained from secondary basins. A distinct lack of detritus particles with sufficient nutrient sources were marked as unreliable records. Unfortunately, histor- and calcium content (Hruska,ˇ 1991a; Tichá et al., 2012) are con- ical sources only considered the occurrence of freshwater pearl sidered to be the main factors preventing the reproduction and mussels in rivers and streams, rather than the quantitative esti- survival of juveniles in most of the residual Czech populations