An experiment to save and breed clams rescued three years ago from a creek that developers planned to pave over is a partial success, according to scientists who've found thriving adult clams but very few young in the south branch of the Kishwaukee River in Huntley.
After two days last week of mucking about in the waterway, Shedd Aquarium researchers found about 300 seemingly healthy adult heelsplitters, fat muskets, giant floaters and other species of the nearly 1,200 specimens moved in 1999.
But they found just six young clams--and four of those had been broken open and eaten by muskrats.
The researchers had hoped to find dozens of young clams thriving among the older ones that had been moved to the diverted portion of the river just before Del Webb began developing Sun City Huntley in that area.
The experiment is important, the scientists say, because clams--or mussels--keep rivers and creeks clean by filtering water as they eat bacteria and tiny plants.
Mussels, in addition to being food for other critters, are a barometer of water quality. If the clams thrive in this newly created stretch of the creek, it will be a sign the ecosystem is thriving too.
Humans and invasive species have decimated native freshwater mussels in the last century. In the early 1900s, the button industry harvested tons of shells every year to make buttons. Later, others discovered that the shells of freshwater mussels could be inserted into oysters to stimulate the formation of pearls--a practice that is still widespread.
Also, invasive species such as zebra mussels competed with native species for food and space, while pollution from insecticides and fertilizers damaged habitats. Development caused rivers and streams to fill with silt, further damaging the mussels' habitat.
In the early 20th Century, Illinois had 80 species of mussels. Six of those are now extinct everywhere, and another 11 are no longer found in the state. Half of Illinois' 63 remaining species are endangered or close to becoming endangered.
"It is one of the most endangered groups of animals in North America," said Kevin Cummings, a research scientist at the Illinois Natural History Survey. "Seventy percent of the 300 species in North America are in trouble."
Roger Klocek, who heads the project for the Shedd Aquarium, said other builders could benefit from Del Webb's experience at Sun City as more effort is made to help plants and animals co-exist with development.
When the developers began plotting Sun City in 1997, they saw that the south branch of the Kishwaukee ran through a tract where they wanted a road and houses. Over the years, the river had been straightened and deepened by farmers for use as a drainage ditch.
The developers wanted to divert the river and restore it to a more natural flow--skirting the road and houses. The state told the developers that, if they wanted to move the creek, they also must move the clams.
Although researchers hoped for more than the half-dozen young clams they found, it's still the best evidence that the mussels are beginning to thrive in their new home, Klocek said.
"This is pretty healthy,' said Klocek, senior conservation biologist at the Shedd Aquarium. "Not too much mortality--and indications of young ones coming up."
It's possible that a recent storm made it difficult for the scientists to find the couple of dozen young clams they had hoped to see. Not finding them doesn't mean they aren't there, Klocek noted.
Based on the specimens found, Klocek said it appears most of the 1,200 clams that were moved have survived.
He'll be studying the data over the next few weeks, looking, for example, at how much the clams have grown and how many have died. He hopes to soon have a better understanding of how well the clams have adapted in the last three years.
And he'll return in three years for another look.