A study out of Novia Scotia found that the number of different benthic invertebrate species — small creatures like mayflies and caddisflies that live in the silt at the bottom of waterways — was significantly lower downstream from fish farms than previous counts, according to the CBC.
Benthic invertebrates are considered the “building blocks” of rivers and streams because they supply larger species with a ready source of food. The researchers discovered that while there were plenty of individual benthic invertebrates in the water, there were fewer distinct species. Only the species that could tolerate nutrient overload from fish feces and undigested fish food coming from upstream aquaculture sites had survived. The farms were growing Chinook salmon, Artic char and brook trout.
“It really kind of amazes me [that this is the first study] given the number of hatcheries and land-based hatcheries we have in Atlantic Canada,” Susanna Fuller, marine conservation coordinator at the Ecology Action Centre said. Novia Scotia alone has 21 fish hatcheries. The governmental unit that conducted the research, however, was recently cut due to budget constraints, so future studies into the environmental impact of aquaculture are not planned.