Casco Bay Islands and Its Watersheds Natural Resources & Data

Casco Bay Islands

Casco Bay is a part of the northwest Atlantic’s Gulf of Maine, located between New England and Nova Scotia. With 200 square miles of water between Cape Elizabeth and Cape Small in Phippsburg, and 578 miles of shoreline, Casco Bay is a large and ecologically diverse estuary – a place where rivers meet the sea. Its watershed includes large, deep Sebago Lake, and extends all the way up to the mountains near Bethel. The Fore, Presumpscot, Royal and Stroudwater Rivers flow out and around its roughly 785 islands, islets and exposed ledges, reducing ocean salinity, and transporting nutrients and pollutants out over the heavier salt water. Casco Bay supports 850 species of marine life, contains over 8,200 acres of eelgrass beds and two major seaweed forests, all enhanced by its oxygen rich, colder waters. A changing climate, rising seas, and threats to the health of this system have extremely local impacts, affecting coves, embayments and all of its tidal waters. We depend on volunteers from every community around the Bay to help track changes through Oceanside Conservation Trust and its partner reporting projects.


Friends of Casco Bay

To improve environmental health of Casco Bay.

Casco Bay Estuary Partnership

Collaborative partnership to restore & enhance Casco Bay and its 1,000 sq. mile watershed.

Wild Seed Project, Portland, Maine.

Native plants of Maine and the Northeast. The Wild Seed Project seeks to inspire all to take action to increase the presence of native plants grown from wild seed. It leads a significant rewilding program here in Maine, to help people create and repopulate landscapes with abundant wild plants that safeguard wildlife habitat, support biodiversity and mitigate the effects of climate change. Its interactive website offers extensive education and outreach. Wild Seed ethically collects and sells wild and uncultivated (non-cloned) forms of native plants.

Maine Audubon, Falmouth, Maine.

Maine Audubon's headquarters are at Gilsland Farm in Falmouth. Maine Audubon produces and delivers hands-on, experiential nature programs, leads trips and expeditions to connect people to wildlife and nature, promotes awareness of lake ecology through its statewide, annual Loon Count, offers education projects to Bring Nature Home, and promotes tools for expanding renewable energy, participates in Maine’s Annual Bird Counts, Brook Trout Survey, and Wildlife Road Watch.

Maine Department of Inland Fisheries & Wildlife

Maine IF&W is charged to preserve and enhance inland fisheries and wildlife, oversees and promotes the safe enjoyment of Maine’s outdoor industries, and seeks to balance Maine’s wildlife, life and folks.

Maine Island Trail Association

A stakeholder-based conservation organization built around small boaters as stewards of 200+ Maine Islands from Kittery to Cobscook Bay.

Casco Bay Islands Alliance

Casco Bay Islands Alliance, formerly CBIDA, brings together Southern Casco Bay’s island communities to provide community input and wisdom on pressing current events like the proposed development of Fort Gorges in Portland Harbor.

Gulf of Maine Research Institute

Interdisciplinary science of the GOM ecosystem, community and class specific education, with particular emphasis on the economic and market effects and interactions with our Gulf of Maine ocean environment.

Portland Water District, Remote Learning Education

High quality water resources educational programming for teacher, students, and parents: excellent short videos on water and wastewater services by PWD; water source protection; Brook trout; Discovering Water.

Casco Bay Watershed

Casco Bay Watershed


Bird Academy

The Cornell Lab

Cornell Lab’s 100 year-old bird science and education arm has excellent courses for all levels.

Marine Mammals

Marine Mammals of Maine

Marine Mammals of Maine provides response, assistance and care for stranded marine animals. It also provides public education about marine animals and the environment.

Seacoast Science Center

Advancing wildlife conservation through stranded marine mammal response, care, and community outreach in New Hampshire and Northern Massachusetts. Meet the seals and porpoises of the Gulf of Maine.


NOAA Fisheries

Conservation and management of sustainable fisheries, aquaculture, species & habitat.

American Lobster Habitat Factsheet

When the deeper water temperature rises above 42°F, our lobsters move in toward the coast.

"Due to its wide tidal variations and varied underwater topography, Maine has the most extensive intertidal habitat (the area between high and low tides) found along the U.S. Atlantic Coast."  Casco Bay Estuary Partnership