Historically, the Petitcodiac River watershed and its tributaries used to be home to a diverse community of migratory fish, including thousands of Inner Bay of Fundy Atlantic Salmon and American Shad, an important economic resource for the local fishermen. The construction of the causeway in 1968 created an obstruction to natural fish passage, resulting in significant changes to the river’s native fish communities. Several species have completely disappeared (American Shad, Atlantic Salmon, Atlantic Tomcod and Striped Bass) while others have been greatly reduced (Alewife, Blueback Herring, Rainbow Smelt and Brook Trout).
This list also includes the Dwarf Wedgemussel, which used to live in abundance in the Petitcodiac River, its sole known location in the country. Today, this small mussel is extirpated from Canada and found in only nine American watersheds. Its elimination is attributed to the Petitcodiac causeway.
Four years of monitoring following the restoration of fish passage by opening the causeway gates found several native anadromous species in the upper reaches of the river, American Shad, Striped Bass, and Atlantic Tomcod, that had not been seen there in decades. Of these, the latter two have shown sustained and progressive increases in numbers over the years, while invasive non-native Smallmouth Bass have declined.
Consequently, it is clear from these results that the fish community of the Petitcodiac has the capacity to recover, given the right conditions, and appears to be on its way to doing so.
| Common Name | Latin Name | Status* |
| Alewife, Gasperau | Alosa pseudoharengus | (r) |
| American Eel | Anguilla rostrata | (r) |
| American Shad | Alosa sapidissima | (e) |
| Atlantic Salmon | Salmo salar | (e) |
| Atlantic Tomcod | Microgadus tomcod | (probably e) |
| Blueback Herring | Alosa aestivalis | (r) |
| Brook Trout | Salvelinus fontinalis | (r) |
| Brown Bullhead | Ameiurus nebulosus | (i) |
| Chain Pickerel | Esox niger | (i) |
| Rainbow Smelt | Osmerus mordax | (r) |
| Smallmouth Bass | Micropterus dolomieui | (i) |
| Striped Bass | Morone saxatilis | (e) |
| White Perch | Morone americana | N/A |
| White Sucker | Catostomus commersoni | N/ |
•Current status of the specie in the Petitcodiac watershed: (e) eliminated, (r) reduced population, (i) illegally introduced
The education poster that follows, produced by Riverkeeper in 2005, lists the various marine species of the Petitcodiac. The restoration of fish passage at the Petitcodiac causeway will allow most of these species to be re-established in our ecosystem.
