Smolt wheel provides important data on Middle River’s embattled salmon
TOM AYERS CAPE BRETON BUREAU
Published June 1, 2015 - 7:17pm
MIDDLE RIVER — Anglers won’t have to work around the contraption parked mid-stream in the Middle River for much longer. The smolt run is just about done.
The smolt wheel — properly known as a rotary screw trap — has spent its fifth season collecting young salmon as part of a research project by the Unama’ki Institute for Natural Resources, which is the resource management body run by the five First Nations in Cape Breton.
Smolts are generally two or three-year-old salmon, 15 to 20 centimetres long, that are making their way to the sea, where they will eat, grow and mature before returning to their birth river to spawn.
“The smolt wheel is only in place when the smolt are running,” Shelley Denny, the institute’s director of research and stewardship, said Monday in an interview along the river’s edge.
“Usually it’s done by this time, but it’s a little late this year.”
The institute annually advertises the timing and location of the smolt wheel, with a warning to boaters that the structure is tethered in place and could be a hazard. However, the Middle River is not usually busy with traffic, other than anglers walking the shoreline or wading in to bag a few trout.
The trap has an important job, catching any fish that swim into it during the three or four weeks it is in the water. Denny said at this time of year researchers are finding mostly salmon smolts, with a few sticklebacks and a trout or two thrown in.
The other species are immediately released downstream to reduce the chances of being caught again, but the smolts are retained briefly to be measured for length and weight. A small sample of scales are taken for later aging in the lab, and the tail fin is clipped to mark the fish as having been caught.
The smolts are then released upstream, and the number of recaptures indicates how well the population is doing at moving downriver toward salt water in the Bras d’Or Lake.
“What we’re really trying to figure out is how many are leaving the river and heading to sea,” said Denny.
While the Middle River is one of several salmon-producing rivers in Cape Breton, the population has been below conservation levels for years, meaning no fish can be taken without permanently damaging the population.
And that includes Mi’kmaq, who are being asked to avoid taking any salmon from the Middle River, even for ceremonial purposes, due to the struggling population.
Other rivers, such as the Margaree in Inverness County, have populations above the conservation level, where salmon can be removed without affecting the long-term viability of the stock.
However, this year, the federal government instituted a catch-and-release policy on all Atlantic salmon across the Atlantic provinces, in an effort to slow the fish’s steady overall decline in population.
Estimates indicate about two-thirds of the Atlantic salmon population has disappeared in the last 30 years. Scientists and government officials are trying to determine exactly why increasingly fewer salmon are surviving their trip to sea.
Global warming, predation by seals and overfishing by other countries are all being blamed.
In addition to its work on smolts, the Unama’ki institute also works on adult salmon counts with researchers from Fisheries and Oceans Canada and Cape Breton University, and all three share data and discuss conservation measures.
University researchers have also begun tagging some of the Middle River smolts with radio transmitters that can be tracked in the ocean by a huge network of audio receivers.
Population counts on the Middle River were very good in 2012 and 2013, but the numbers were down last year, said Denny.
While the data is preliminary, the Middle River seems to be rebounding, she said.
“Right now, Middle River sits here,” said Denny, holding her left hand at eye level and her right hand about six or eight centimetres below her left.
“And last year, it sat here,” she said, dropping her right hand about 30 centimetres. “The Middle River is not fishable for salmon.”