Fisheries Blog

Although many of us know about the common game species, the non-game species are less well known — not surprising since it is tough to observe fish in their natural habitats. Illinois has over 200 fish species occupying a wide variety of waters, ranging from large rivers to small streams, and from small ponds to Lake Michigan. Our non-game species blog is highlighting those lesser-known Illinois species. We hope you enjoy the pictures and the information on their life histories, distribution, family ties, and other interesting facts about this fascinating group of animals.

WSDWestern Sand Darter
Ammocrypta clara

The Western Sand Darter is a very small member of the Perch family (Percidae).This family also includes several well-known sportfish species such as Walleye, Sauger and Yellow Perch. This is an interesting and diverse family containing 239 species worldwide, primarily limited to freshwater habitats. Perches are the largest group of freshwater fishes in North America with over 150 species. The Chicago Region has a total of 16 species in this family, including 13 Darters. The small diminutive Darters, having reduced swim bladders, are generally benthic (bottom dwellers). Unlike most other fishes that effortlessly suspend in the water column, Darters fall to the bottom when not actively moving. They are specialist feeders, relying on insects and other small crustaceans, and are generally sensitive to habitat and water quality degradation, therefore serving as a useful indicator species.

The Western Sand Darter has a slender, elongated body with a pointed head and terminal mouth. Adults are small, rarely exceeding three inches in length. Their coloration is very pale, appearing almost translucent or, as described by ichthyologists, pellucid. The Western Sand Darter, true to its name, lives almost exclusively over sand in rivers and creeks with moderate to fast current. Its translucent, pale color makes it incredibly well camouflaged over sand. In fact, it is known to partially bury itself in the substrate often with only its eyes and mouth exposed. They are primarily nocturnal in habit.

The Western Sand Darter is rare throughout the entire State of Illinois and is listed as an Endangered Species. The one pictured above was collected recently from Horse Creek, a tributary to the Kankakee River in northeastern Illinois. Only one specimen was found and, you guessed it, in sand over flowing water — a very lucky find given their elusive habits and general scarcity. When first collected the fish looked rather pale and non-descript. However, when placed in the photo chamber in bright sunlight, its true colors were revealed with bright orange and black markings along the lateral line, back, and head. This specimen was photographed live in a specially designed aquarium and was then released alive to return to its sandy dwelling.

Photo Credit: Dr. Philip Willink