The winged mapleleaf mussel was once found in 34 rivers in 12 states. Today, it has only survived in the St. Croix. The endangered Higgins’ eye mussel also lives in the St. Croix.
Both species of rare mussels are threatened by the invasive Zebra mussel, as well as water quality issues. The Xcel Energy dam at St. Croix Falls is just above the river’s prime habitat for the winged mapleleaf. The power company agreed in 2006 to operate the dam to mimic natural water flows, preventing sedimentation and fluctuating flows which previously destroyed the gravel beds necessary for healthy mussels.
The Saint Croix Snaketail dragonfly (Ophiogomphus susbehcha) was first identified in the river and is only found in a few rivers in the immediate region. The Minnesota Department of Natural Resources says:
In general, ophiogomphid larvae prefer clear, swift flowing rivers. Adults patrol these rivers and forage in adjacent wetlands, lowland forests, and mature upland forests with closed canopy and low understory. They tend to disappear from cleared or cultivated regions due to the reduction of sheltered shoreline vegetation for adults, and changes in flow and siltation in the larval habitat.
The Snaketail Dragonfly larvae usually emerges from sandy bottoms of the river in late May to late June, and can be seen flying into early August. More about the Snaketail Dragonfly »