A conservative estimate of $200 million in damage to the regional economy caused by invasive species in the Great Lakes should give Congress reason to enact stricter controls on the oceangoing ships entering the St. Lawrence Seaway.

The economic toll on the lakes' regional economy estimated by a University of Notre Dame study does not include the cost to Canada and other parts of the United States where invasive species have migrated after being dumped into the lakes or St. Lawrence River. Study author David Lodge called the $200 million figure "the tip of the iceberg."

The Great Lakes are home to 186 invasive species such as zebra mussels, the round goby and quagga mussels. Fifty-seven species hitched a ride in ballast water in oceangoing vessels entering the Seaway since it opened in 1959.

The largest economic loss has been a $123.5 million yearly hit to the sport fishing industry. The loss from people who enjoy wildlife watching is estimated at $47.6 million with municipalities, power plants and industry along the lakes and river sustaining $27 million in damages. Commercial fishing losses are put at $2.1 million a year. The figures do not reflect property damage from invasive species or harm to inland lakes or other parts of the country.

Given the source of many invasive species, it has been suggested that oceangoing ships be kept out of the St. Lawrence Seaway, particularly in the absence of strict national regulations on ballast water. The National Research Council, though, rejected that proposal due to its economic consequences. A 2005 study by the Joyce Foundation put the costs at $55 million to transport freight by other means, which would be a quarter of the damage now done by invasive species and likely to grow.

The council said that the "single estimate with recognized limitations and imperfections is not a robust basis for informing a major policy decision."

As an alternative, the St. Lawrence Seaway Development Corp. has established ballast-exchange rules that require ships to flush their ballast tanks at sea to kill or dump invasive species before entering the waterway. Yet stronger measures urged by the council are stalled in Congress.

The council recommended stricter standards for ballast water and better systems for monitoring compliance with the exchange requirements. The House has approved a measure requiring ballast treatment systems on board ships entering the Seaway. The latest reports should be cause for action.