Fishing activities have direct impacts on targeted populations by increasing their mortality. However, it is difficult to know the changes to the ecosystem due to fishing activities since they have been going on for centuries. It is also a challenge to assess the cumulative impact of fisheries on the ecosystem as a whole rather than on the populations being fished.
Fishing gear can impact on benthic, non-targeted demersal and pelagic organisms as well as on physical and biological habitats. These impacts may include short-term effects such as sediment re-suspension, digging or realignment of the bottom, destruction of habitat and organisms as well as longer-term impacts resulting in altered sediment structure, benthic communities, ecosystem processes or recruitment to fisheries (Gordon et al. 2002). However, no experimental studies specific to the Gulf of St. Lawrence have been published.
Abandoned fishing gear is a concern as well. For example, while lobster and crab traps may be equipped with biodegradable escape mechanisms, fishnets often continue to catch fish until they degrade. Dredging and marine disposal of waste and sewage may also have some impacts on the loss of habitat and local species abundance and dispersion.
Finally, land-based activities, particularly those that take place along the coastline, have the potential to impact the marine habitat. Along the Gulf of St. Lawrence, these include pulp and paper mills, mineral processing operations, more than 200 fish processing plants, more than 1,000 dams on waterways, approximately 1.5 million hectares of agricultural land and untreated sewage released from many municipalities bordering the Gulf of St. Lawrence.