Shortnose sturgeon and Atlantic sturgeon in the Penobscot River 
Since spring of 2006, University of Maine researchers have documented over 400 shortnose sturgeon in the Penobscot River, the first confirmed captures since 1978. In addition, close to�80 Atlantic sturgeon have also been caught and released. Under a NOAA-Fisheries Endangered Species permit (#1595-02) all have been externally and internally tagged for later identification to estimate population size. A subset of these individuals have been tagged with ultrasonic tags, used to determine specific migratory patterns and habitat use in the river. These tags are detected by receivers sitting on the river bottom; the receivers are attached to pink bouys that you can see while driving along the lower river. An interesting behavioral pattern that has been documented since 2007 is the movement of some individuals (both shortnose and Atlantic) between the Penobscot River and the Kennebec River. This is interesting because theory "has it" that shortnose sturgeon do not leave  the river they hatch in. They were believed to move into the estuaries of those rivers but never to make coastal migrations. Current data from the Penobscot River shows that shortnose sturgeon move to a well-defined area of the river in mid-October and stay through the winter; In April,when water temperature in the river rises above 7 degrees C, sturgeon, if ready to reproduce, move to their spawning location. Researchers have followed tagged fish and set egg collectors to try to confirm the sturgeon are spawning in the river. Once they confirm spawning behavior, they will stop collecting eggs due to the endangered status of the population. Atlantic sturgeon have been a little more elusive to researchers. Fewer Atlantic sturgeon have been captured (close to 80) and tagged (19) than shortnose sturgeon. However, valuable information on habitat use and movement patterns has been collected for Penobscot Atlantic sturgeon. Individuals of this species also frequent the Kennebec and some of them return to the Penobscot. Last summer, Atlantic sturgeon were tracked to a very defined section of the river during summer months, and then they left in the fall. Both species of sturgeon, shortnose and Atlantic, are primitive fishes with rows of boney, armor-like plates on their sides and skeletons of cartilage rather than bones. Sturgeon are bottom feeders; they move along the river bottom, disturbing the substrate with their mouths and ingest plants and animals into their tube-like mouth.  Atlantic sturgeon are larger than the shortnose (the shortnose sturgeon rarely grows more than 4 feet in length). Large, slow-to-mature fish, they can grow to 18 feet in length and are designed to be effective bottom feeders. Being anadromous in nature, they return to their native rivers to spawn. Most of their growth is believed to occur out at sea where they feed on various invertebrates and small fish. In Maine waters, law protects both the Atlantic sturgeon and the shortnose sturgeon.
Additional research took place in 2008 and 2009 to allow researchers to refine population estimates for the Penobscot River and conduct the spawning part of the study, made possible by funding from NOAA-Fisheries, the Maine Department of Marine Resources, and The Nature Conservancy (2008). Receivers were put at the mouths of other major rivers in Maine, including the Union, Narraguagus, St. George, Medomak, and Damariscotta Rivers to learn more about where shortnose sturgeon are going in coastal Maine. Not long ago, researchers were unaware that they migrated between river systems. The Penobscot River historically supported spawning populations of both the endangered shortnose sturgeon and the Atlantic sturgeon. With implementation of the Penobscot River Restoration Project, 100% of the historic spawning habitat for both species of sturgeon will be restored. (Update information provided by UMaine School of Marine Sciences Assistant Professor Gayle Zydlewski). Photo by Christopher Holbrook. | | Scroll down for links to video and underwater sonar images
WATCH UNDERWATER IMAGING SONAR OF STURGEON (Video images taken pursuant to ESA permit number 1595). VIDEO OF RESEARCHERS COLLECTING DATA ON STURGEON (Video images taken pursuant to ESA permit number 1595-02). December 2008 Bangor Daily News article LISTEN TO OCTOBER 2007 MPBN STORY BY MURRAY CARPENTER: Radio clip READ MORE: NOAA press release (2006) and original Bangor Daily News article |
