I successfully pitched this story about sea ducks eating the mussels cultivated on longslines by PEI mussel growers to G & M editors.
This year’s unseasonably warm winter weather around Prince Edward Island is a good news/bad news story depending on the point of view. Good news for sea ducks who have no need to fly further south because they can find lots to eat in the ice-free bays and inlets around the island. Bad news for cultivated mussel growers tired of seeing their lines of maturing shellfish treated like a paddle-up sushi bar for wild birds.
PEI provides 90 per cent of Canadian mussels for export and the industry is worth $24 million ($65 million if you include economic spinoffs) to the PEI economy. Overwintering sea ducks are skimming about $1 million off the top of that income by dining on cultured mussels grown on longlines suspended below the surface of the water, according to provincial Fisheries and Aquaculture spokesman Richard Gallant,
“If left unattended, a couple of hundred sea birds can do significant damage,” he says.
Jean MacDonald of PEI’s Aquaculture Alliance agrees. Some growers on PEI’s north shore, where the problem is most significant, have lost 40 to 50 per cent of their crop, she says.
The mussel growers are accustomed to the sea ducks flocking to the PEI shoreline to fatten up during fall migration season. Two types of ducks, the Greater Scaup and the Long-tailed, have become mussel epicures. They discovered that cultured mussels take a lot less paddling and diving to find than the mussels that grow naturally on the ocean floor. Not only that, the line-grown shellfish also have thinner shells and a higher meat content. To add insult to injury for mussel growers, scientists at Aquanet, a national research network, have found that Scaup ducks knock just as many mussels off the longline as they eat, further compounding the loss. And the longer they linger, the bigger that loss becomes.
If the weather was what it used to be, the water in the estuaries where the mussel farms are located would be frozen and mussel growers would have a rest from worrying about predators at their lines. “When you have a normal winter, the ducks head south,” says Mr. Gallant. However, when the Island gets another “normal” winter is a matter of speculation. Ms. MacDonald says the ducks have outstayed their welcome for at least three years; one local mussel farmer says he noticed the trend began a decade ago.
This means that methods used to discourage the ducks from eating the mussels, none of them perfect and one of them prompting noise complaints, have to be extended until the water finally freezes up. Growers will startle the skittish ducks away from the mussel lines by cruising up and down the estuaries in their boats during the daytime. “Physical presence is the best deterrent, but at this time of year, that can get difficult,” says Mr. Gallant, citing the wind and colder temperatures that increase the danger and discomfort of running a boat at this time of year, to say nothing of the expense to the mussel grower. However, this is at best a temporary method, and researchers found that the Scaup ducks altered their behaviour in response. The birds normally feed during the day, but in the mussel cultivation areas, they are now feeding at night, rendering daytime scaring techniques for this type of duck virtually useless. Some growers are also setting off a propane cannon, three shots every half-hour, from 6:30 a.m. to 9 p.m., to startle to birds, an unpopular solution with area residents seeking a tranquil seaside life.
Researchers looking for a nature-friendly solution to the problem hold some hope for a biodegradable socking material that could be pulled over the mussels on the longlines, sheltering them from the bills of predating ducks. A paper detailing results of tests conducted in PEI using the sock was published in the December 2006 edition of Aquaculture International Journal.
“The sock showed promise, but it needs considerable improvement before growers would be able to use it,” says Professor Diana Hamilton of Mount Allison University, one of the paper’s authors. Problems encountered include the fact that the sock didn’t biodegrade quickly enough and trapped some growing mussels inside, affecting growth and survival. Some mussels also grew partway outside the sock, resulting in malformed shells which would mean problems in marketing the mussels. Research continues on this and other potential solutions to the problem.