Guagas Lake - Courtesy of Nelson Cloud

Freshwater mussels are an important part of a healthy aquatic ecosystem. As benthic organisms, they play a vital role in the composition of aquatic food webs, nutrient cycling and energy flow. They also help maintain water quality as filter feeders. Freshwater mussels are considered to be the most threatened taxonomic group in North America. Although some rivers in New Brunswick have been surveyed for freshwater mussels, very few surveys have been done in the Miramichi River watershed. Little is thus known about which species are present, and their abundance and distribution. Particularly due to limited access, the Northwest Miramichi River has never been surveyed prior to this project, but areas on the Southwest Miramichi River have been surveyed in the past by freshwater mussel specialist Ms. Kate Bredin. Ms. Bredin also has a special interest in a rare freshwater mussel species, the Brook Floater, that she has discovered in the Miramichi River, which increases the importance of continuing such surveys in the watershed in order to understand the status of this species.

Brook Floater found on the Taxis River

The Brook Floater (Alasmidonta varicosea) has currently been assessed by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) and has a National General Status Rank of "special concern" in New Brunswick. With the discovery of this mussel in the Southwest Miramichi, further freshwater mussel surveys in the Miramichi River will help delineate the extent of this rare species in the Miramichi watershed. Brook Floaters are declining throughout their range in the US due to pollution and alteration of river habitats. It is hoped the Miramichi River may harbour an important population of this species.

North Pole Stream below Palisades

The Eastern Pearlshell is the most numerous freshwater mussel species in the Miramichi River watershed as thousands of these mussels have been recorded. The Miramichi River is world renowned for its Atlantic salmon fishing and also very popular for trout fishing. Both of these fish species are common hosts for the Eastern Pearlshell’s larval stage. Also, with limited industrial impacts the water quality and mussel habitat conditions on most of the Miramichi River is very good.

The second most common freshwater mussel MREAC discovered during the surveys was the Eastern Elliptio, discovering hundreds of specimens at 5 of the 30 sites. The Eastern Floater was discovered at two sites, one site was a lake and one was the Napan River at a section with lake-like conditions. The Brook Floater was discovered during the second year of sampling at two sites. Both of these sites were on new tributaries where the Brook Floater was not known to exist; naming the Taxis River and Barnaby River. With this discovery, the Miramichi River is becoming a more important link to the survival of this freshwater mussel species. In order to further understand the mussel population size and distribution, MREAC comitted a third year of surveys focused on these two tributaries. Out of the 15 sites surveyed, new Brook Floaters were only found at one site on the Barnaby.

Below is a map showing sample sites for MREAC’s three years of freshwater mussel surveys (2008, 2009 & 2010) along with Ms. Bredin’s sites (2002 & 2006). This map demonstrates the distribution of freshwater mussels on the Miramichi to date.