Aug 30, 2008 - 04:30 AM

By Reka Szekely

ONTARIO -- Oshawa resident Allan Bass has been fishing the Great Lakes and the rivers that flow into them for 45 years and he’s noticed some changes.

“The lakes are much clearer now than they ever were,” he said.

The clarity, which many residents along the lakes initially welcomed, is a sign of big trouble in the lakes because it’s caused by the proliferation of zebra and quagga mussels, invasive species from Easter Europe brought in ships’ ballast water in the late 1980s. The mussels have irrevocably changed the waters.

“If you look at a lake like Lake Erie, 90 per cent of the mussels are quagga mussels,” said John Cooper of the Lake Erie management unit for the Ministry of Natural Resources,

And they’re not alone. The lakes are averaging a new invasive species every eight months, he said. Since 1959, when the St. Lawrence seaway opened, more than two-thirds of the 84 invasive species in the lakes have been introduced via shipping. They include the super tiny, such as viral hemorrhagic septicemia, which is an infectious fish disease that causes fish to hemorrhage from their organs, skin and muscles, to several species of waterfleas that feast on zooplankton to fish such as the Eurasian ruffe. In all the lakes except Superior, the state of the lakes is deteriorating due to invasive species.

“Because they don’t have the natural predators here, they start to multiply like mad and they push out the native species,” said John Jackson, program director for Great Lakes United, a coalition of citizen’s groups in Canada and the U.S. working to protect the lakes.

But the issue of invaders is not a new issue. The opening of canals between the lakes and the St. Lawrence in the earlier part of the century allowed sea lamprey to infiltrate the lakes, decimating fish populations, including the lake trout. A parasite, sea lamprey latch on to fish such as trout and suck nutrients out them, leaving their victims to die of blood loss or infection.

Coupled with over fishing, the trout virtually disappeared from the Great Lakes, except for isolated pockets in Georgian Bay in Lake Ontario and Lake Superior. But programs to control the lamprey population, including using lampricide in the rivers where the parasite spawns, have led to some recovery.

“We have a program in Lake Erie trying to re-establish lake trout as well. It’s showing slow signs or recovery and we seem to be getting better results in Lake Huron and Lake Superior,” said Mr. Cooper.

As well, the Ministry of Natural Resources in Ontario and its American counterparts now stock non-native sport fish such as rainbow trout and chinook salmon. In some of the lakes, such as Lake Huron, stocking rates are decreasing as the fish are starting to reproduce naturally. In fact, the state of salmon and trout is improving at least slightly in all of the lakes except Lake Ontario, which remains unchanged and has the second highest stocking rate after Lake Michigan.

But the biggest stress on the lakes’ eco-system from invaders isn’t at the top of the food chain, but at the bottom.

The spread of the mussels is linked to the decline in preyfish, which are eaten by predators like trout and salmon. In every lake except Lake Superior, the state of preyfish is deteriorating.

“They’re filtering the food they need out of the water, microscopic food items fish depend on,” said Mr. Cooper.

This is because the mussels are out competing native organisms such as a tiny shrimp-like organism called Diporeia. At the bottom of a healthy lake, Diporeia make up as much as 70 per cent of the living biomass, but as it stands, the abundance of Diporeia is considered poor and deteriorating in all the lakes except Superior. When the organism is replaced with hard-shelled indigestible mussels, the preyfish are left with nothing to eat.

And not only are preyfish, such as the sculpin, losing their food source, they face fierce competition from another invasive species, the round goby. Brought in via ballast water in 1990, the goby has a voracious appetite for fish eggs, including those of lake trout.

But there are signs the goby is integrating into the local food web.

“Quite a few native fish and bird species like to eat gobys,” said Mr. Cooper, citing smallmouth bass as an example. The goby is also one of the few animals to feed on zebra and quagga mussels. The problem is that since the mussels act as filters, they tend to accumulate toxins which then get worked back up the food chain via the goby.

Not only is the presence of invaders an ecological nightmare, it’s an economic one as well.

Preliminary results from a study by two American researchers show invasive species are responsible for $200 million in annual economic losses each year. The scientists used American data, but they say it likely applies to Canada as well. By far the biggest chunk of losses, $123 million, comes from losses in the sport fishing industry. Depending on the lake, the researchers estimated participation in sport fishing was 11 to 35 per cent less than it would have been without invasive species in the water. Another $2 million per year is lost from the commercial fishery in the lakes.

As well, some scientists are theorizing that the mussels are responsible for the explosion of algae along some shorelines, including in the GTA.

“We believe they are somehow improving the supply of phosphorus to the algae,” said University of Waterloo biologist Ralph Smith, who is looking at the problem.

Dr. Smith’s work is funded by the Town of Ajax, the Region of Durham, Ontario Power Generation and government research grants.

The  algae is costing both the Region and OPG money when it clogs water intakes from the lakes to water treatment plants and nuclear power plants. OPG wouldn’t put a price tag on it, but a representative said on some occasions reactors at the Pickering power plant have had to be shut down until the intakes were unclogged.

Meanwhile, other invasive species such as the Asian carp are literally knocking at the door. Released into the Mississippi river during flooding, the fish have made their way up to Chicago and are being kept out of the Great Lakes by an electric fence.

“The Asian carp in particular are the invasive species on the horizon that we don’t want in the great lakes,” said Mr. Cooper.

But can they be kept out?

“I think we can. We’re just going to have be vigilant,” he said.

Part 3 of the series on the lakes will look at how the clean up of the lakes is going.