Une espèce unique de palourdes (myes) devient extincte dans la rivière Petitcodiac du Nouveau- Brunswick; est-ce que d'autres vont suivre?

Dans cet article, Daniel Leblanc, un Petitcodiac Riverkeeper, nous parle de ce mollusque, l'Alasmidonte naine.

Il déclare que le pont-jetée sur la Petitcodiac (construit entre Moncton
et Riverview en 1968) a causé 
la première extinction d'une espèce de palourdes au Canada. 

L'extirpation de cette espèce unique de 
mollusque fut annoncée pendant que le gouvernement étudiait quoi faire
afin de sauvegarder ce système riverain. 

Le nombre de ce mollusque
avait diminué tellement que le U.S. Fish and Wildlife Service l'ajoutait
à sa liste d'espèces en péril en 1990. Aucune mesure similaire n'a été
introduite au Canada.

Il s'agit encore d'un autre triste exemple de l'incapacité de protéger
notre faune nationale.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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.

 

Unique clam species goes extinct
in New Brunswick's
Petitcodiac River
Others to follow?


Daniel Leblanc
Petitcodiac Riverkeepers / Sentinelles
December, 2000

 

he Petitcodiac River causeway built between Moncton and Riverview in 1968 has caused the first known extinction of a clam species in Canada. This front-page story appeared in the Ottawa Citizen on Tuesday November 28th, alongside another important national story featuring the Liberal Government's federal election victory!

=======   Dwarf Wedge Mussel  =======


(photo: National Wildlife Foundation.)


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 1990. 
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 Petitcodiac.

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.
(photo: Environment Canada)

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 bass.

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?