Captive breeding of the endangered freshwater pearl mussel Margaritifera margaritifera

Abstract

Freshwater pearl mussels (Unionidae: Bivalvia) rank among the most endangered aquatic invertebrates, and this has recently prompted a number of initiatives designed to propagate the species through captive breeding. Yet there are few guidelines to aid in freshwater mussel culture for conservation, and few or no results on the fate of released juveniles. We reviewed various ex situ strategies for freshwater mussel conservation with emphasis on the freshwater pearl mussel Margaritifera margaritifera (L.), one of the most critically endangered unionids. Captive breeding could help safeguard critically endangered populations, but current rearing methods need to be optimised. Areas in particular need of research include the collection and storage of viable glochidia, the development of efficient rearing systems, and the formulation of algal diets. Likewise, the degree of host specificity warrants further investigation, as this will largely dictate the success of reintroduction programmes. Finally, we note that more information is needed on the degree of genetic structuring and post-release survival before translocation programmes can be recommended. As with other conservation projects, captive breeding of the freshwater pearl mussel cannot compensate for loss of critical habitats and is likely to be most efficient in combination with in situ conservation, not in isolation.

Transcriptomic responses of the endangered freshwater mussel Margaritifera margaritifera to trace metal contamination in the Dronne River, France

“…Previous studies evidenced high toxicity of Cu to unionid mussels, especially in young stages (see Young 2005). Since freshwater pearl mussels do not reach sexual maturity until an age of 10 to 20 years (Thomas et al 2010), the comprehension of the susceptibility of this age class to Cu pollution is of crucial interest for conservation planning actions.…”

Conservation status of the freshwater pearl mussel Margaritifera margaritifera in Portugal

“…On the contrary, and due to their extended life span, if adults can survive in present disturbed conditions, conservation may be possible if the appropriate management measures, that guarantee effective reproduction and future recruitment, are implemented (Hastie, 2011). In the same vein, and due to the high fertility, captive breeding and future stocking in the wild can be a viable solution if the suitable conditions are restored (Preston et al, 2007;Bolland et al, 2010;Thomas et al, 2010;Gum et al, 2011).…”

An alien fish threatens an endangered parasitic bivalve: the relationship between brook trout (Salvelinus fontinalis) and freshwater pearl mussel (Margaritifera margaritifera) in northern Europe

“…Many conservation strategies for the restoration of FPM populations have been developed; habitat protection and restoration , Bolland et al 2010, Geist 2010, Horton et al 2015 probably are the primary strategies but methods such as reintroduction of mussels (Young and Williams 1983b, Valovirta 1993, Beasley and Roberts 1999, Bolland et al 2010, Geist 2010, release of glochidia-infected fish (Buddensiek 1995, Geist et al 2006, Thomas et al 2010, Simon et al 2015 and artificial culture of mussels (Buddensiek 1995, Preston et al 2007, Geist 2010, Schmidt and Vandré 2010, Thomas et al 2010, Gum et al 2011, Simon et al 2015 are also widely used. However, despite the conservation activities, increased freshwater mussel research (see e.g.…”

“…However, despite the conservation activities, increased freshwater mussel research (see e.g. Thomas et al 2010) and the conservation status of FPM afforded by EU directives and national legislation (see Lopes-Lima et al 2016), the decline of FPM populations has continued and even steepened. Furthermore, there are predictions of more populations becoming extinct in the future (Bauer 1983, Valovirta 1990, Beasley et al 1998.…”

“…Thus, my results are consistent with these findings, indicating that the differences between FPM populations in terms of the host specificity may be a universal phenomenon. Therefore, even though loss of host fish has often been suggested as a potential contributor to the collapse of FPM (Young and Williams 1983b, Geist 2010, Makhrov et al 2011, Ostrovsky and Popov 2011, Oulasvirta 2011, Lopes-Lima et al 2016, this host specificity, if occurring also elsewhere, may be an additional, less understood explanation for the collapse, for the absence of young mussels and for the unsuccessful outcomes of the attempts to reestablish the declined FPM populations via host salmonid stocking (Bauer 1988, Valovirta 1990, 1993, Geist et al 2006, Thomas et al 2010, Simon et al 2015. The host specificity should certainly be investigated more comprehensively throughout the range of FPM.…”