When we’re invited to someone’s home, we’ll bring a gift for our host. Once there, we’ll do our part to keep up conversation and avoid spilling red wine on the furniture. It’s what good guests do.
But if you’re an anadromous fish, these rules of etiquette don’t apply. Each spring and summer, you’ll show up to a nearby freshwater wetland. Once there, you’ll proceed to spawn, defecate, and in some cases, die. Yet this behaviour at a marsh isn’t just acceptable – it’s encouraged.
Anadromous fish species, like salmon, alewife, and rainbow smelt, hatch in freshwater environments but spend the majority of their lives at sea, then return when it’s time to spawn.
When these fish species re-enter freshwater rivers, lakes or wetlands, they will release what scientists call “marine-derived nutrients.” These nutrients improve freshwater wetlands by enriching vegetation, soil, and insects in riparian areas.
These enhancements are all good news for ducks, who enjoy an increase in plants and insects, which they rely on for shelter and food. That’s why Ducks Unlimited Canada (DUC) is working to help ensure these migrating fish receive the warm welcome they deserve.
(Re)connecting the finned and feathered at Missaquash Marsh
DUC’s efforts to reconnect wetland to ocean, and fish to freshwater, is best embodied at Missaquash Marsh, situated along the upper north shore of the Bay of Fundy, forming the border between Nova Scotia and New Brunswick. “It’s a great example of our work, and it shows how we’re trying to close the gap between wetlands, waterfowl and fish,” says Nic McLellan, DUC’s Atlantic science co-ordinator.
Once a saltwater marsh, Missaquash Marsh was emptied in the 1600s by European settlers through tidal diking and drainage. For approximately 250 years, the area was farmed.
But over time, soil quality deteriorated around the upper bay, and the cost of continuing to use the land for agriculture became prohibitive. In the early 1960s, DUC recognized the potential to return some of these diked marshlands to productive waterfowl habitat.
In 1965, DUC engineers installed impoundment and water control structures, restoring Missaquash Marsh as a freshwater wetland. This was followed in 1971 with the introduction of a fishway. “Often times, when we restore a wetland, we also install water control structures to regulate water levels. In cases where these structures acted as barriers to anadromous fish species, we also constructed fishways,” explains McLellan. Sometimes referred to as ladders or passages, fishways are intended to help fish access systems upstream.
Fishway or “no way”?
“A number of years ago we realized that we would need to rebuild several DUC fishways that had been built 30 to 40 years ago,” says Geoff Harding, DUC’s head of major projects in Atlantic Canada.
“But we didn’t know the passage efficiency of our current fishways. And at that time, we didn’t have enough science or technical knowledge to answer this question. So we reached out to other groups,” says Harding.
In 2013, DUC partnered with Acadia University, University of Prince Edward Island, Irving Oil Ltd., and provincial governments to study several existing fishways and test new designs. “Since 2013 we have tagged thousands of weaker swimming anadromous fish species like alewife and monitored their movements,” says McLellan.
Over the course of four field seasons, researchers learned the fishway installed at Missaquash Marsh wasn’t passing alewife as effectively as another nearby fishway.
Ensuring alewife get the “invitation”
To address the problem, this summer DUC will work to secure funding to rebuild the fishway at Missaqaush Marsh. The new structure will be modelled after the fishway at Amherst Marsh, which has a more gradual incline.
According to Harding, it was a “lack of understanding” that drove DUC to study fishways. “And over the last five years we’ve become leaders in the effort to improve fish passage,” he says.
This is good news for both the finned and feathered. Because despite their bad behaviour, anadromous fish are the life of the party – and the marsh.
Big fish(way manager) in Atlantic Canada
DUC has constructed fishways since the 1970s, in partnership with federal and provincial governments. DUC now oversees 151 fishways, and is recognized as the largest manager of these structures in Atlantic Canada.