The Gulf of Maine, bordering the jagged coastline of Maine, represents one of the most biologically productive marine environments in the North Atlantic. Its cold, nutrient-rich waters attract a diverse array of migratory cetaceans. The seasonal abundance of zooplankton and small schooling fish provides a rich summer feeding ground, drawing whales from their warmer breeding grounds further south.
The Most Frequently Sighted Baleen Whales
The large baleen whales that consistently appear in the Gulf of Maine during the feeding season are the Humpback, Fin, and Minke whales. Humpback whales, measuring 40 to 50 feet in length and weighing up to 40 tons, are known for their distinctively long, white-edged pectoral fins and spectacular surface behaviors like breaching and tail-slapping. Researchers use the unique patterns on the underside of the tail fluke, which is often raised before a deep dive, to identify individuals. Humpbacks primarily feed on small schooling fish, such as herring, and krill, often employing a cooperative hunting technique called bubble-net feeding.
Fin whales are the second-largest species, reaching lengths of up to 70 to 80 feet. A key identifying feature is their asymmetrical coloring, characterized by a white lower jaw on the right side only. These massive filter feeders consume vast quantities of copepods, krill, and small fish, often feeding on their side to engulf prey.
The Minke whale is the smallest of the baleen whales, typically growing to about 20 to 30 feet long. Minke whales are distinguished by a sharp, pointed snout and a prominent white band on each flipper, sometimes referred to as “minke mittens.” Unlike their larger relatives, Minke whales tend to be solitary and less prone to dramatic surface behaviors, often feeding alone or in very small groups closer to shore.
Endangered and Transient Whale Species
The Gulf of Maine is occasionally visited by species that are either endangered or transient, utilizing the area less predictably than the regulars. The North Atlantic Right Whale is the most significant of these, with a global population estimated to be under 370 individuals. This species lacks a dorsal fin and is identified by rough, calcified patches of skin on its head called callosities, which appear white due to colonization by small whale lice. Right whales are filter feeders, relying heavily on small zooplankton called Calanus finmarchicus and are particularly threatened by entanglement in fishing gear and collisions with large vessels.
The Sei whale is a fast-swimming species that is also listed as endangered. Sei whales are occasional visitors to the Gulf, with their presence often dictated by the distribution of their prey, which includes copepods and small schooling fish. The presence of Sei whales can be tied to the vertical migration patterns of their copepod food source.
The area also hosts smaller cetaceans, such as the Harbor Porpoise, which is often encountered by whale watchers. Harbor porpoises are distinct from dolphins, possessing a smaller size, a triangular dorsal fin, and spade-shaped teeth. These animals typically travel in small groups of two or three and prefer the more coastal habitats of bays and harbors. Less frequently, toothed whales like Pilot whales are sighted, often traveling in cohesive, social pods in the deeper offshore waters.
Seasonal Appearance and Viewing Areas
The presence of large whales in Maine is highly seasonal, peaking during the warm months when the Gulf of Maine offers its most abundant food supply. The prime viewing season begins in late spring, around May, and extends through the early fall, typically ending in October before the whales migrate south.
Whale-watching tours commonly depart from coastal towns like Bar Harbor, Portland, and Boothbay Harbor. Vessels often travel 30 to 50 miles offshore to reach the most productive feeding grounds. These offshore banks, such as Jeffreys Ledge or areas in proximity to Stellwagen Bank National Marine Sanctuary, are known for consistent whale activity. The convergence of currents and bathymetry in these regions concentrates the plankton and small fish, creating a reliable summer buffet for the arriving cetaceans.