Evaluate the effects of invasive exotic fish on freshwater mussels indigenous to the St. Lawrence

Context and project description

Several species of freshwater mussels in the St. Lawrence are at risk: six are on the list of species likely to be designated as threatened or vulnerable under Quebec legislation, and another is considered to be endangered by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). Factors that affect their population include the degradation of habitats, the deterioration of water quality, climate change, and the introduction of invasive species. Freshwater mussels are also sensitive to disturbances that occur in fish communities. In fact, several species of fish play an unknown but crucial role in the reproduction and spread of freshwater mussels, as they "incubate" their larvae, referred to as “glochidia”, in their gills, on their skin, or on their fins. The arrival of exotic fish, such as the round goby, could compromise these essential relations between mussels and their natural host fish.

The purpose of this research project is to evaluate the hypothesis that the round goby would act as an “imposter” host for the larvae of certain species of indigenous mussels and would damage their recruitment and spread. The situation could also be the opposite: the goby could be a compatible host for mussel larvae, which would thus be favoured.


This project revealed that the round goby is not a competent host for incubating larvae of the eastern lampmussel, a common freshwater mussel species in the St. Lawrence. That discovery indicates that this invasive exotic fish is likely to disturb mussel reproduction and dispersal.

The scientists who conducted this study designed a method for testing the ability of exotic fish species to incubate larvae of native mussels. They also developed a tool for identifying larva species in order to tell them apart by analyzing their DNA sequences. This promising tool makes it possible to identify the most important natural hosts in the life cycle of the freshwater mussels living in the St. Lawrence watershed. Two scientific articles presenting the results of the project are currently being written.

Participating departments

Government of Canada

  • Environment and Climate Change Canada

Government of Quebec

  • Ministère du Développement durable, de l'Environnement et de la Lutte contre les changements climatiques
  • Ministère des Forêts, de la Faune et des Parcs