"Contract Award" Survey of fish hosts for the freshwater pearl mussel in 12 rivers

Tender description

The Contract has now been awarded to Paul Johnson Associates. The freshwater pearl mussel (Margaritifera margaritifera) is listed on Annex II and Annex V of the EU Habitats Directive. The species is considered to be critically endangered in Ireland (Byrne et al., 2009) and Europe (Cuttleod et al., 2011), and its conservation status was bad, when reported under Article 17 of the Habitats Directive in 2007 and again in 2013 (Moorkens et al., 2007 a and b, NPWS 2013). Reproduction in the freshwater pearl mussel involves the release of large numbers of larvae, called glochidia, between July and September each year. Young salmonids, typically 0+ and 1+ fish, act as a temporary host for the glochidia. The glochidia attach to the fish’s gill filaments and become encysted. They survive on the fish, developing into young mussels and fall off in early summer (normally June). In Ireland, trout Salmo trutta L. and Atlantic salmon Salmo salar have been shown to host freshwater pearl mussel glochidia (Johnston and associates, 2009 a and b; Moorkens, 1996, 1999). In May 2009, as part of the work to develop catchment (‘sub-basin’) plans for SAC populations of the freshwater pearl mussel, 27 catchments were electro-fished for juvenile salmonids to establish the fish hosts (Johnston and associates, 2009 a and b). Glochidia were found at 12 of the 27 catchments. At the remaining 15, glochidia may already have detached from fish. The study established that glochidia were almost exclusively found on age 1 fish and that the individual mussel populations used salmon or trout as hosts, but not both (Johnston and associates, 2009 a and b). The purpose of this request for tender is to procure an electrofishing survey of fish hosts for the freshwater pearl mussel in 12 rivers, to fill knowledge gaps and inform the Department’s national conservation strategy for the species. (Refer to RFT)