Fauna

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MAMMALS
of the Penobscot River and Bay

River Otter
Otters are not uncommon in the Penobscot and its tributaries. Otters occupy freshwater and brackish portions of the river and its tributaries, and they can stay underwater for up to two minutes. The mom raises the young for a year after they are born, teaching them to swim and other life skills. Their thick fur is the most durable of all North American furbearers, and otter pelts have been in demand ever since Europeans first arrived. Over 1,112 otters were harvested statewide in 2005, fetching $65 a pelt. According to Maine Department of Inland Fisheries and Wildlife, they are trapped in November and December by the few remaining licensed trappers in the state, although their overall population status is unknown. A study in the Journal of Mammalogy found that otters in Maine seem to have a stable reproductive rate, but mercury pollution may be a problem (Docktor et al. 1987). Otters eat mostly fish, crayfish, and amphibians, which accumulate mercury. Studies by the BioDiversity Research Institute have looked at mercury levels in otters near the mercury-polluted Holtrachem site in Orrington. Mercury levels in brains were below the concentrations that cause acute death, but levels in their fur were high, indicating chronic exposure (Yates et al. 2005).

Seals
Penobscot Bay is home to harbor and grey seals, as well as a few species of "ice seals" who occasionally wander south from subarctic regions. Harbor seals are the most abundant, and their numbers have increased greatly since passage of the Marine Mammal Protection Act in 1972. The population estimate has increased from 10,500 in 1981 to approximately 30,900 being counted in Maine in 1997. Harbor seals "haul out" on both tidally exposed ledges and small, uninhabited islands throughout Penobscot Bay and the outer islands. Some harbor seals from southern New England travel to Penobscot Bay just before pupping season, which occurs during May and June. Mothers will take their pups with them on swimming excursions around the bay, teaching them to dive for fish. Seals have been observed as far as Bangor in the Penobscot River . In winter, some portion of the population moves offshore into the Gulf of Maine, a portion moves south to Cape Cod , and a portion remains in coastal waters of Maine (Gilbert et al. 2005; Waring et al. 2006).

Grey seals were historically abundant, disappeared for a while, and have returned to Penobscot Bay in steadily increasing numbers in the last 15 years. Grey seals pup in January, at two known locations including one island in Penobscot Bay.

Seals prefer to eat silver hake, redfish, cod, flounder, and herring, but they will eat other things, including salmon. What they eat while in the river and estuary is still undocumented. In May 1888, the New York Times reported that "A large school of seals have followed salmon into Penobscot Bay and are slaughtering them. In return owners of salmon weir have organized and they shoot seals as they come out upon the rocks for air. They have killed 10 this season. The skins are worthless." In 1896, Hugh Smith of the United States Fish Commission visited the Penobscot River to assess the fisheries there and found that "seals are known to kill a great many salmon in Penobscot Bay and the lower river," and the state at the time paid a $1 bounty for seal scalps (Smith 1897). According to James Gilbert, marine mammal researcher at the University of Maine, there are only five cases of salmon being found in seal stomachs.

Seals are currently protected under the federal Marine Mammal Protection Act.

Seal populations in Penobscot Bay were monitored from 1981 to 2001 (surveyed every 5-7 years). Data are available on harbor and grey seal adults and pups in a digital atlas (Dow et al. 2006). An XML version of the atlas that can be integrated with GoogleEarth is available from
Dr. Gilbert's Web page. This version shows all sites on the Coast of Maine where seals were observed in any survey flight between 1981 and 2001.

Porpoises & Whales
Other marine mammals in Penobscot Bay include harbor porpoises (who calve in the bay in summer), and right, humpback, minke, and fin whales in outer Penobscot Bay and the nearby Gulf of Maine. Their prey includes sand lance, herring, and menhaden.

One whaling steamer, the Hurricane , was registered in Rockland Maine in 1885; two whaling stations were established on Vinalhaven, at Greene island in 1885 (by Gen. Davis Tilson and Maj. W.S. White) and Carver's Harbor in the early 1900s (Reeves 2002).