Density and abundance of the Freshwater Pearl Mussel, Margaritifera margaritifera , in the Kennebecasis River, New Brunswick and evidence of recent recruitment

Freshwater Pearl Mussel, Margaritifera margaritifera (L., 1758) populations are endangered or threatened throughout Europe, and those in eastern Canada are believed to be some of the most abundant populations remaining worldwide. Although M. margaritifera occurs widely in Atlantic Canada, there is little information to allow its conservation status in the region to be assessed or to place these populations in a global context. Using 0.25 m 2 survey quadrats, maximum densities of M. margaritifera in six mussel beds on the Kennebecasis River and a tributary in southeastern New Brunswick were found to range from 12 to 200 m -2 . Mean densities at the five mainstem sites ranged from to 1.9 m -2 (SE±0.4) to 16.0 m -2 (±4.3). Mean density on the tributary stream was 1.2 m -2 (SE±0.7). Abundance of M. margaritifera at the six sites ranged from 4,536 (SE±2,600) to 55,520 (SE±14,768) and together the six mussel beds supported an estimated 161,315 Freshwater Pearl Mussels. The presence of juvenile M. margaritifera as small as 11.5 mm at the most upstream site, and Freshwater Pearl Mussels <30 mm at all sites, indicates that there had been recruitment of M. margaritifera juveniles in the Kennebecasis River in the 4–6 years prior to the 2007–2008 study.