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Great Lakes Article:

Exotic marine species threaten Great Lakes
Associated Press
Published June 14, 2004

MINNEAPOLIS — Vast populations of foreign fish, mussels and other creatures have invaded and damaged the Great Lakes in the last few decades, creating a more difficult problem than the industrial contamination that fouled the lakes in the 1960s, the Star Tribune reported in Sunday editions.

The invasion began in the early 1800s, but accelerated after the St. Lawrence Seaway opened the lakes to oceangoing ships in 1959. More than 40 per cent of the 179 alien species have been documented since then, with most arriving by ship from Europe or Asia, according to research data analysed by the newspaper.

A new invader is identified in the lakes about every seven months, faster than scientists can study them.

Henry Regier, a professor emeritus of zoology and environmental studies at the University of Toronto, describes the Great Lakes basin as "a sick system." In 50 years of studying the lakes, he said, he has never seen such dramatic changes.

Prof. James Carlton, director of the Maritime Studies Program at Williams College in Mystic, Conn., said the lakes have been permanently modified "on one of the greatest scales in any aquatic environment in the world."

Unlike industrial pollution, much of the new damage is nearly invisible, hidden in the lakes' murky depths. Yet biologists who study lakes say the evidence is mounting that the unintended introductions of species from around the world could soon dominate the lakes' ecology, the Star Tribune reported.

On the shores of Lake Erie, the destruction can be seen in the deaths of birds who have eaten the round goby, a 10- to 15-centimetre-long European fish with bulging eyes that has found a new home in the Great Lakes.

Often the meal is a death sentence. More than 50,000 loons and other birds died after eating gobies over the past five years _ victims of poisoning. Scientists say the gobies become toxic food by ingesting quagga mussels, another recent invader from Europe, which accumulate botulinus toxin from the lake bottom.

So many dead birds have washed ashore during recent fall migrations that beach patrols hauled them away with ATVs and flatbed trucks.

A critical link in the Great Links food chain is the half-centimetre-long Diporeia, a pale orange shrimplike organism that lives on the bottom of lakes. Loaded with fat, they long have been a high-energy, abundant food source for fish in the Great Lakes. But over the past decade, Diporeia have vanished from more than 44,000 square kilometres of lake bottom _ an area more than twice the size of New Jersey. Every lake except Superior has been affected.

Scientists began to document the losses in the early 1990s, in areas where zebra or quagga mussels had invaded. As the fish food disappeared, so did native fish, especially the commercially valuable whitefish, which depend on Diporeia for up to 70 per cent of their diet.

The speed and success of a single species' invasion can be stunning. Scientists found a few dozen Eurasian ruffe in the Duluth harbour in 1986. The small, spiny, perch-like fish from Europe exploded to two million by 1991 and to more than eight million in 1998 before declining slightly, according to federal estimates. It now is the most abundant fish species in the harbour.

One reason that some invasive species are surviving and proliferating is that harbours and estuaries are cleaner today. Taxpayers and industries invested billions of dollars to improve sewage treatment, remove phosphorus and reduce chemicals, allowing the Great Lakes and their native fish and wildlife to progress toward recovery during the 1970s and 1980s. Invaders are undercutting those achievements.

The changes affect not only fish, but also the smallest plants, invertebrates, snails and mollusks. For example, 20 species of native mussels lived in Lake St. Clair, part of the waterway between Lake Huron and Lake Erie, in 1986. Two years later, zebra mussels spread into the lake. By 1997, all of the native mussels were gone except in a few shallow areas.

Invaders also pave the way for future intruders. The newcomers sometimes alter the habitat in ways that help other alien creatures to thrive. For example, invasive gobies spread quickly in areas where zebra mussels have become established because the gobies eat the mussels. In other places, zebra mussels attach themselves to non-native Eurasian watermilfoil plants. The mussels gain a place to live, while the milfoil grows better because the clinging mussels filter and clear the water.

Commercial ships have been the main carriers of the invaders, which can ride in the water that empty ships carry as ballast and then dump as they take on cargo upon reaching harbour.

U.S. fish farms also contribute to the problem. Two kinds of Asian carp imported to clean U.S. fish farm ponds and tanks escaped into southern waterways in the early 1980s. They have spread up the Mississippi River and its tributaries toward Lake Michigan, jeopardizing a $4.5-billion commercial and recreational Great Lakes fishery.

Invasive species also have entered the lakes through bait buckets, as anglers intentionally or inadvertently dumped them into the water. Unwanted aquarium fish have been released into waterways because their owners thought it was a humane or convenient way to dispose of them.

About a third of the invasive species in the Great Lakes basin are aquatic plants, such as Eurasian watermilfoil, which have been spread by ships, boats, trailers, garden nurseries and other means. This vegetation can overtake lakes and interfere with boating, fishing and swimming.

Michigan has 185 infested lakes, Wisconsin has 44, and Ontario has dozens, especially along a highway of interconnected lakes, rivers and canals that extends more than 320 kilometres between lakes Ontario and Huron. The spread of invasive species in Ontario threatens a $1.4-billion-a-year recreational fishing industry.

 

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