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After a Century, Fish Return to Historic Habitat in Maine

For the first time in more than 100 years, endangered shortnose sturgeon have reached habitat in the Penobscot River that had been blocked by dams. University of Maine researchers confirmed that three shortnose sturgeon swam past dam removal sites in Milford, Maine. The fish had been fitted with acoustic tags so that scientists could track their movements in the river.

Sturgeon are often called "living fossils" because they are very similar to their earliest fossil forms. Their long lives (more than 50 years) and bony-plated bodies also make them unique. Historically, shortnose and Atlantic sturgeon had spawning populations in the Penobscot River as far upstream as the site of the current Milford dam. They provided an important food and trade source to native populations and early European settlers.

Overharvest and loss of suitable habitat due to dams and pollution led to declines in shortnose sturgeon populations. They were listed as endangered under the U.S. Endangered Species Act (ESA) in 1967. Gulf of Maine populations of Atlantic sturgeon were listed as threatened under the ESA in 2012.

Today, a network of sound receivers from Penobscot Bay up to the Milford Dam detects the movement and location of tagged fish. In mid-October, the receivers detected three individual fish. These fish have since been tracked joining other individuals in wintering habitat near Brewer, Maine.

Habitat access is essential for the recovery of these species. The removal of the Veazie Dam is only a portion of the Penobscot River Restoration Project. When combined with the removal of Great Works Dam in 2012, this project restored 100 percent of historic sturgeon habitat in the Penobscot. Construction of a nature-like fish bypass at the Howland Dam in 2015 also improved habitat access for native migratory fish native, including Atlantic salmon and river herring.   

Posted December 22, 2015

After measurement and implantation of a small tagging device, graduate student L. Izzo releases a shortnose sturgeon back into the Penobscot (ESA Permit #16036 compliant, photo courtesy G. Zydlewski).