London Free Press

Passage of fish ongoing snag at Springbank Dam

ENVIRONMENT: Concerned city engineers will ask the city politicians for more funding to carry out another year of tests

Last Updated: 11th January 2010, 11:15am

The controversial Springbank Dam is getting mixed grades at letting fish pass upstream to spawn.

Those grades -- based on the latest test results -- are so mixed city engineers will ask city politicians Monday for money for at least one more year of tests.

"Some results are good and some results are bad," Rick Goldt, supervisor of water control structures for the Upper Thames River Conservation Authority, said yesterday.

In both last year and 2008, fish had a harder time passing over the dam than in 2006, before a multimillion-dollar rebuild. Some species had more trouble last year than in 2008.

"The results are not where they want to be," Goldt said.

But there are so many variables, from weather to low samples for some fish species, it's too hard to tell what the long-term trends will be, said Pat Donnelly, urban watershed manager for London.

"We need at least one more year of monitoring," he said. "The more you measure the more certain you can be."

Donnelly has helped prepare a report heading to the environment and transportation committee Monday seeking about $53,000 for a third year of tests.

The tests are the first of their kind in Ontario, he said.

"Many people will benefit from this."

Damaged by a flood in 2000, the dam was shut down in 2006 for a $6.8-million rebuild that was supposed to be completed by 2008.

The Ontario Natural Resources Ministry required the city to run tests to ensure the rebuilt dam, when gates are open in the spring, does not obstruct the passage of fish.

Biotactic Inc. conducted tests for the city in 2006 before the dam was rebuilt to see how well fish passed over the old structure.

Tests were done in 2008 and again last year to see how well fish swim over the rebuilt dam when the gates are open.

The gates, meanwhile, malfunctioned and broke during tests in 2008.

Since then the dam's broken gates have remained open, sparking lawsuits -- and debate about the necessity of closing the gates each summer to raise water levels in the river downtown.

The yearly fish passage results are sure to spark more debate and ammunition for anglers who want the dam decommissioned or left open all year.

The fish are caught downstream, tagged with a radio transmitter then released.

The researchers then determine what proportion of the tagged fish get to within 30 metres of the dam -- establishing how attractive the dam is to fish.

They also determine what proportion of the fish attracted to the dam make it over the dam and how long it takes those fish to pass over.

The researchers suggest a number of reasons for the difficulty in getting over the dam, including back eddies created by the foundations that slow fish down.

"We may have to do some tweaking," Donnelly said.

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  • In 2009, Springbank Dam was particularly unattractive to two species studied -- the white sucker and the smallmouth bass. These "attraction efficiencies" were lower in 2009 than in both 2008 and 2006.

  • The shorthead redhorse fared better getting over the dam in 2009 than in 2008, but still not up to 2006 levels.

  • The proportion of smallmouth bass making it over dropped considerably from 2008, which was lower again than in 2006.

  • Test results for fish passing over the dam varied widely. Vandalism of survey equipment at the dam made it impossible to collect data for the white sucker.