21.03.2016
Doctoral Dissertation

29.4.2016 FM Jouni Salonen (Faculty of Mathematics and Science, Aquatic Sciences)

Time:

29.4.2016 12:00 — 15:00


Location: Ylistonmaki , YAA303
Release: 29 Apr 2016 The role of salmonid fishes in conservation of the endangered freshwater pearl mussel (Salonen)
M.Sc. Jouni Salonen defends his doctoral dissertation in Aquatic Sciences ”The role of salmonid fishes in conservation of the endangered freshwater pearl mussel (Margaritifera margaritifera)”. Opponent Professor Jürgen Geist (Technische Universität München, Germany) and custos Professor Jouni Taskinen (University of Jyväskylä). The doctoral dissertation is held in English.

M.Sc. Jouni Salonen defends his doctoral dissertation in Aquatic Sciences ”The role of salmonid fishes in conservation of the endangered freshwater pearl mussel (Margaritifera margaritifera)”. Opponent Professor Jürgen Geist (Technische Universität München, Germany) and custos Professor Jouni Taskinen (University of Jyväskylä). The doctoral dissertation is held in English.

Freshwater pearl mussels (Margaritifera margaritifera) have declined substantially during the 20th century, and the number of successful restoration operations has remained limited. One apparent explanation for that is the mussels’ complex life cycle, which includes larval (glochidia) parasitism on the gills of a salmonid fish. Generally, Atlantic salmon and brown trout have been considered equally suitable host fish for the freshwater pearl mussel, but in this study different mussel populations were shown to have strong differences in their ability to use different salmonid species as their hosts. Most importantly, Atlantic salmon was clearly a better host for mussels living in large river channels, to which the salmon has had no route to migrate due to hydropower dams since 1960s. Therefore, the lack of the most suitable host fish, salmon, has evidently contributed the collapse of the freshwater pearl mussel in these rivers. Atlantic salmon should thus be restored in their original river habitats for successful conservation of these mussel populations. However, interestingly in small headwater tributaries brown trout was the best, or the only suitable, host fish. Furthermore, an indication of mussels’ adaptation to the local, resident salmonid population within the most suitable host species was also found. These results highlight the conservation importance of the original salmonid populations throughout the range of the freshwater pearl mussel. Moreover, a widely introduced invasive salmonid, brook trout, was found to be a generally unsuitable host for this mussel species. Thus, and due to the tendency of brook trout to replace the native brown trout, the spread of this invader is an additional threat to the freshwater pearl mussel. Finally, a new approach to search for freshwater pearl mussel populations was developed. This method involves electrofishing and quick visual examination of the gills of captured salmonids, i.e. the potential hosts of this mussel. The method was successfully tested in the River Iijoki catchment, as 3 ‘new’, previously unknown populations were found.

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Jouni Salonen

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jouni.k.salonen@jyu.fi