The Committee on the Status of Endangered Wildlife in Canada, which
draws up Canada's Endangered Species List, declared the Dwarf wedge
mussel (Alasmidonta heterodon) officially "extirpated"
(wiped out) from Canada last year; the only known place in which the
mussel lived in Canada was the Petitcodiac River.
Ironically, the extirpation of this unique mussel species was
declared while the province of New Brunswick and the Government of
Canada were studying what to do in order to save this river system. The
study that determined the Dwarf wedge mussel extinct was also carried
out while Canadian federal legislation to protect endangered species was
shelved on two separate occasions in the last decade.
All freshwater clams (including mussels) need one or several types of
"host" fish to complete their development. When you cut off
fish passage, the clams lose their hosts and eventually die. In the case
of this little New Brunswick mussel, the causeway built across the
Petitcodiac River in the late 1960s caused the migration of salmon and
other fish species in the river to be eliminated.
Just a century ago, the Dwarf wedge mussel could be found in at least
70 locations in 15 major watersheds along the Atlantic front from New
Brunswick to North Carolina. Now this small mussel, which rarely exceeds
two inches in length, is limited to only nine watersheds in the United
States and none in Canada. The mussel's numbers have dropped so low that
the U.S. Fish and Wildlife Service listed it as endangered in
No similar measures were introduced in Canada.
Species like the Dwarf wedge mussel have their own unique function in
the ecosystem. And saving these small, freshwater shellfishes is
important on several levels.
(photo: National Wildlife Foundation.)
Freshwater mussels cleanse their aquatic ecosystem, filtering debris
and other material out of stream waters and help to keep waters clean.
Their role is beneficial to other stream-dwelling animals, from fish to
frogs. Moreover, declining mussel populations warn of dangerous levels
of pollution and other ills in water systems. Damaged streams can pose
health hazards to people as well as to stream organisms. By protecting
the Dwarf wedge mussel and other native freshwater mussels we provide a
safer, healthier environment for mussels and humans alike, as well as to
the other species that depend upon riparian areas to survive. But
is the extinction of this little mussel of apparently "no
commercial value" just a sign of more bad news to come for the
survival of endangered species in New Brunswick?
In the Petitcodiac River alone, additional species of freshwater
mussels may be lost forever from the watershed if the causeway remains
closed. Researchers from the Department of Fisheries and Oceans (DFO)
recently found at least three other species of clams barely surviving in
the watershed. The life cycles of most of these are not fully
understood, but there are some for which we can make clear predictions.
The Eastern Pearlshell mussel (Margaritifera margaritifera) is
globally endangered (in both the United States and Europe) and DFO
researchers predict that its population in the Petitcodiac is destined
for extermination with the causeway closed. The fish host for this clam
larva is a salmonid, probably the Atlantic salmon. The only places DFO
found any evidence of recent reproduction in the Petitcodiac was where
salmon had been restocked since the causeway was built in 1968. Only
large and older individuals of the Eastern Pearlshell mussel have been
found in the river system, attesting to the fact that only
non-reproducing populations can survive under the present
conditions. But, like the Dwarf wedge mussel, eventually it will
disappear from places where the host no longer has access.
The Brook Floater (Alasmidonta varicosa) has a status of
"threatened" in the United States. It is rare in the
Petitcodiac and is not found in Canada outside of New Brunswick and Nova
Scotia. DFO researchers believe the host may be the alewife or blueback
herring. Both of these two fish species are severally threatened in the
The Triangle Floater (Alasmidonta undulata) has a status of
"special concern" in the United States. It is very rare in the
Petitcodiac system but does occur elsewhere in Canada, not
restricted to the Maritimes. The host of this clam species is presently
unknown by DFO researchers.
We have known for over 20 years that something is going terribly
wrong on the Petitcodiac, and that failure to restore free flow to this
river would cause further species to be eliminated. From the early
1980's to today, while the provincial and federal governments proceeded
to study the effects of restoring the Petitcodiac, at least four
anadromous fish species which used to frequent this River in great
numbers were eliminated from the system: the distinct Inner Bay of Fundy
Atlantic salmon species, American shad, Atlantic tomcod and Striped
This happened while fisheries' experts, the federal and provincial
Departments of the Environment and even the Minister of Fisheries, whose
duty it is to protect fish habitat in this country, knew of the risks
involved and instead opted to "proceed with caution".
This extraordinary failure by those accountable for the protection of
our national wildlife begs the question: what will it take for those
mandated to protect endangered species in Canada to act?