Sep 21, 2014
From the adjacent sandbar, it looks like a diving school gone awry. Two wet-suited divers are connected to oxygen lines. A couple others have masks and snorkels. A few more are on their hands and knees, wading—and groping—through the shallows. Every couple minutes, one hoists another mussel; adding to the inventory.
“You are looking for coarser gravel, but not big cobblestones. They have to push through the substrate”, explains Vance Polton, DNR fisheries technician. We are standing knee deep in the Iowa River, below Iowa City; returning a ‘Wabash pig toe’ to the sandy bottom. Onshore, small piles of live mussels are inventoried, measured growth; then returned to the water…survivors in an age not friendly to many underwater creatures.Iowa’s mussel dilemma is mirrored throughout North America. A dozen of 54 known Iowa species are gone. At least half of the others are endangered or threatened. That wake-up call is what brings up to 50 biologists, students and volunteers for a week of wading and grabbing river bottom lumps; hoping for elk toes, three-ridges, pocketbooks or fat muckets. If nothing else, freshwater clams have great names!
This summer, the target river was the Iowa; historically, a good ‘mussel’ river. “Fish and mussels have ‘co-evolved’. They somewhat depend on each other”, underscores Scott Gritters, DNR fisheries biologist and annual ringmaster of Iowa’s ‘Mussel Blitz’. “The more mussel species? The better the mussel density. The better our fish populations? The better our water quality.”
The results this year? “It’s one of those ‘glass half full, glass half empty’, scenarios”, assesses Gritters. “We really scoured some areas. We found about 1500 mussels; 20 species. We found some decent populations, but I had hoped for 3000 or so.” His long term concern is that populations cannot handle the cycle of highs and lows of past years; floods, drought, extreme winter cold. Mussels don’t react well to that.
On the upside, the 2014 Blitz turned up another six Higgins’ eye pearly mussels; nearly extinct 40 years ago. Any Higginseyes in the Iowa River were stocked. Raised in hatcheries; they were inoculated as glochidia–larvae–into the gills of fish, which were stocked several years ago. No larger than grains of salt then, the microscopic mussels hung on for several weeks…before dropping off; hopefully into a hospitable gravel bed. To have them show up now, as adults? “It’s a pretty big deal”, applauds Gritters, noting that a couple were gravid females. “It is a way to reintroduce mussels into our rivers. We stock a lot of fish for our anglers and this way we can ‘double dip’, so to speak.”
With all the problems affecting inland mussels, a few glimmers appear from year to year. “People will like our rivers a lot more, if they can support mussels”, says Gritters.