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Encyclopedia Dubuque


"Encyclopedia Dubuque is the online authority for all things Dubuque, written by the people who know the city best.”
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Affiliated with the Local History Network of the State Historical Society of Iowa, and the Iowa Museum Association.


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Higgins' Eye Clam
HIGGINS' EYE CLAM. The Higgins' Eye clam, a federally endangered specie since 1976, first gained community attention when its discovery temporarily threatened construction of the DUBUQUE-WISCONSIN BRIDGE. Found only in the waters of the Upper MISSISSIPPI RIVER and usually in sand or mud near the shoreline, the clam's thick olive green shells range from four to five inches long.

In 1978 LORAS COLLEGE Professor Edward Cawley and a team received an $8,000 contract from the Iowa Department of Transportation to check the construction site for the endangered clam. From thousands of clams brought to the surface, a single, ten-year-old female Higgins' Eye clam was discovered near the Wisconsin shore 950 feet downstream from the proposed construction site of the Dubuque Wisconsin bridge. Young Higgins' Eye are usually carried as parasites of sauger pike until the clams mature. They then fall off the gills of the fish to the river bottom to continue growing.

In 1880 the Higgins' Eye, named supposedly for the man who discovered it near Muscatine in 1857, were relatively common. By 1978, however, there were only four known locations of the clam. Researchers believe the population of the clam has been cut in half within the last one hundred years from such causes as heavy silting due to the construction of dams, over-harvesting during the years of the BUTTON INDUSTRY, turbulence from boat propellers and various types of pollution.

Discovery of the single clam proved not to be a serious problem. The clam had been added to the endangered species list long after the environmental impact reports of the bridge had been filed. It was expected that efforts would be made to protect the habitat.

In the fall of 2016 an extern from the NATIONAL MISSISSIPPI RIVER MUSEUM AND AQUARIUM challenged high school students from the DUBUQUE COMMUNITY SCHOOL DISTRICT, WAHLERT CATHOLIC HIGH SCHOOL, Western Dubuque, and districts from Fennimore, Wisconsin and Lancaster, Wisconsin to design devices in which to raise the mussel. Following research of the mussel's needs at different stages in their life cycle, models were created and presented to the class. Recordings of the presentations were sent to the museum for consideration. (1)



Ann Schaal

Haws, Dick. "Rare Clam Sets Bridge Plans Astir, The Milwaukee Journal, August 15, 1978, p. 54. Online: http://news.google.com/newspapers?nid=1499&dat=19780815&id=AGgaAAAAIBAJ&sjid=kikEAAAAIBAJ&pg=6945,2957571

1. "Mussel Nurseries," Big River, January-February, 2017, p. 11