The upper Wolf River provides habitat for many species of small fish, each dependent on the clean water and abundant vegetation found in its unchannelized meanders. The Blackstripe Topminnow (Fundulus notatus) can often be seen schooling in shallow water at Bateman Bridge and other spots along the upper Wolf, especially when the river level is low and the water is clear. Look for the light spot on top of its head along with a distinct black stripe down each side. The Topminnow's flattened head and upturned mouth allow it to feed on insects and other small invertebrates at the surface of the water.
Blackstripe Topminnows are found in slow-moving portions of streams and rivers, often near aquatic vegetation. They can also be found in permanent wetlands and lakes. For this species, the size of the stream or water body is less important than the presence of shallow, slow areas with vegetation where spawning occurs. A female lays her eggs one by one in the presence of a male which fertilizes each egg and tucks it away onto an aquatic plant or piece of detritus. The young hatch into the protective shelter of plants which helps them avoid larger fish and other predators. If the riparian edges of a stream are destroyed, the Topminnow's chances for successful reproduction will decline.
The widespread Blackstripe Topminnow prefers meandering rivers and streams like the onces found in the Mississippi River drainage between Illinois and the Gulf of Mexico, which includes the Wolf River. It also occupies parts of the southern drainages of lakes Erie and Michigan. The entire Canadian population of this small freshwater fish lives along a roughly 60 kilometre stretch of the Sydenham River in southwestern Ontario. Discovered only in 1972, the Blackstripe Topminnow is a fairly hardy fish - but its greatest threats come from changes to its habitat due to human activity. The mission of the Wolf River Conservancy is to protect the pristine habitats of the Wolf River so that this and many other species can continue to thrive.