September 26, 2006

by Joe Wilkinson

From the water and muck, a wood and wire mesh cage emerged. Hoisted on board the workboat, the mud in the bottom was hosed overboard. As the debris washed away, dime-sized shells-dozens of them, a hundred or more--appeared. Biologists tallied 870 first-year Higginseye pearly mussels in eight special cages, pulled from the floor of the Dubuque Ice Harbor. For a moment, it seemed hard to believe that the higginseye is an endangered species. This special harvest, though, was the result of hard work and a lot of luck, as biologists learn how to grow mussels in stable surroundings, for eventual release to the wild.

Their fear is that it might be 'too little, too late' to save this integral member of the river community; a species that doesn't get much attention; perhaps because it is hidden on the river bottom for its lifetime. From downtown Coralville to rural Jones County...and along the Upper Mississippi River and tributaries...they're trying to stop the population freefall of mussels.

In this experiment, crews anchored the cages at the back end of the harbor. "We use floats to keep the cages off the bottom", explains U.S. Fish & Wildlife Service biologist Tony Davis. In his wetsuit, he poked around underwater to detach the cages and pull them to the work area. "One of the problems is siltation into the cages. (This way) we keep them out of the sedimentation that has wiped out some years' production." Even still, silt coated the cage bottoms; with the little mussels sprinkled throughout. They had dropped from the gills of largemouth bass, which had been specially inoculated with the larval glochidia before being placed in the cages, a few months prior.

The outcome was a little more realistic on inland streams surveyed late this summer. Stream teams floated and pawed their way through the shallows, looking for older mussels, planted in previous years. With hundreds of staff hours invested, fewer than a dozen higginseyes were confirmed. A few more candidates await DNA determination. One of the 'possibles' came from the Iowa River, at Coralville. The rest came from the Wapsipinicon River, where the first confirmed higginseye in 80 years was located in 2005.

"We have definitely found a few, which is fantastic," proclaims Scott Gritters, a fisheries biologist for the Department of Natural Resources. "We have inoculated some into the gills of fish and turned the fish loose (in the rivers). We have proven that we can restore mussels. We have no idea, though, if the mussels will reproduce." Reproduction will be the next step in this labor intensive, cross-your-fingers quest to restore not only the higginseye, but other species of mussels in trouble as well.

Lately, the 'endangered' label is almost a given. If it is-or was--a mussel, chances are it is endangered...or gone now from Iowa waters. Studies in the 1990s showed that a dozen of the 50 or more known mussel species are gone; extirpated from Iowa waters. Another 15 are on the endangered or threatened species lists. The rest are not far behind. "In the late 1980s, there was a die off of mussels in the Mississippi River. We never fully understood why," offers Gritters. It might have been disease. The explosion of zebra mussels harmed native species, too. Overharvesting mussels played a role, too; a couple times in the last century. Now, though, commercial clamming is illegal in interior waters, and on the Mississippi River, where it borders Iowa and Wisconsin. One bright spot has emerged, with some monitoring sites showing slight upturns in the last few years.

No matter what the contributing factors, experts agree water quality is most critical. Gritters, and others, say reducing soil runoff is a logical first step. But that is easier said than done; with thousands of landowners and reams of government policy in the mix.

So they continue their experimentation into ways to prop up the sagging numbers; not just for higginseyes, but 'yellow sandshells', 'fat muckets' and other species. Seed stock of mature mussels are guarded closely in federal hatcheries. Biologists are actually using 21st Century technology on early 20th Century methods, used when the Mississippi River button industry started to collapse. "This is an attempt to culture them", explains Gritters. "If the numbers keep plunging in the wild, this could keep them from going off the face of the planet."