The only peer-reviewed study examining the environmental impacts of Nova Scotia land-based fish farms has found some negative effects on downstream ecosystem.
A now-defunct unit of Environment Canada conducted research at five sites in 2011 which grow juvenile fish for transfer later to open ocean pens. The results were published earlier this year in the journal, Cogent Environmental Science. The study is the first of its kind in Canada.
Lead researcher Benoit Lalonde said they looked at the health of benthic invertebrates, "the building blocks of what lives in the river or the stream" in areas where water that passed over hatcheries flowed.
Benthic invertebrates are small creatures that live in or on the bottom sediments of rivers, streams and lakes and include immature mayflies and caddisflies.
Researchers found significant changes in biodiversity at two of the sites and some differences at a third.
Less species diversity
In some of the cases there were more of the organisms than expected, but closer inspection of the finding showed the only species that flourished were "pollution tolerant species," said Lalonde, who now works with Environment Canada's water quality monitoring and surveillance division in Dartmouth.
"What we lost there were all the sensitive species," he said.
"The drawback of all of this is that we're losing the diversity … We actually saw that we're losing species downstream of the fish farms where there was an impact, so that's definitely a drawback."
21 land-based sites
He said other Environment Canada research had established a baseline for benthic invertebrate health across Atlantic Canada, so they had substantial data to compare to. Lalonde's previous research near fish farms had found increased nutrients in the water, which he said were likely caused by fish feces or uneaten fish food discharged from the facilities into neighbouring waterways.
"You can never prove anything at the 100 per cent level, but it does show that those fish farms probably do have an impact on the benthic invertebrate populations," he said.
The aquaculture operations studied were growing juvenile fish that included Atlantic salmon, brook trout and Arctic char, with the juvenile fish later sent to open-net ocean farms or to populate streams and rivers.
The operations were located near streams since they require a large amount of high-quality water to operate.
One of the two fish farms in northern Nova Scotia where the largest impact was recorded is no longer in operation. The owner of the second couldn't be reached for comment.
There are currently 21 active land-based aquaculture sites in Nova Scotia including finfish and shellfish hatcheries, according to the provincial Department of Fisheries.
Federal research unit cut
The province has never conducted its own research on the environment effects of land-based aquaculture. In a statement, it said it is currently looking at the way other jurisdictions monitor land-based aquaculture facilities.
Lalonde says that since the data was gathered several years ago, practices in the industry may have changed considerably since then.
However, the Environment Canada unit called "Toxics" that conducted the research was cut. Lalonde says it was unfortunate they couldn't continue the research, as they had hoped to compare data from further upstream and further downstream.
"It definitely something that should be done at some point," he said.
First study of its kind
Susanna Fuller, marine conservation coordinator at the Ecology Action Centre, says downstream impacts should be considered as part of the approval process for any operation.
"It really kind of amazes me [that it's the first study] given the number of hatcheries and land-based hatcheries we have in Atlantic Canada," she said.
"We need to then make decisions about what are these impacts, and also what are the cumulative impacts? If this is the impact of a hatchery, what else is going on in that stream? If we have an impact of open-net aquaculture, what else is going on in that bay?"
Lalonde says ongoing research is necessary to ensure problems doesn't slip through the cracks.
"What we know so far for Nova Scotia anyways and New Brunswick, from the studies that I've done, is there is an impact to water quality, to sediments, to benthic invertebrates," he said.
"But in the same sense, if a farm is using all the wastewater techniques that it can, and the proper techniques, is that impact going to disappear?"