Georgian Bay Islands National Park of Canada
MAJOR HABITATS FOUND IN GEORGIAN BAY
One of the numerous small islands at the northern end of Georgian Bay Islands National Park of Canada© Parks Canada/ W. Waterton/ Collection GBINP
The huge expanse of open water in Georgian Bay is often broken by banks of submerged shoals or by huge smooth rocks which resemble the surfacing backs of whales. These "whalesbacks" are similar to the rocky outcrops mentioned earlier, but their constant exposure to large waves and strong winds warrant treating them separately.
Because of the severe conditions and the isolation from the mainland, little life is found here. Even the diversity of plants is minimal: lichens, grasses and sedges, as well as a few dwarfed trees such as white pine, willow and ninebark.
The water barrier and the lack of cover cause virtually no mammals live here; water snakes and map turtles are virtually the only reptiles. While map turtles are not found on the outermost islands, their large flat shells can sometimes be seen sunning here and there on the small bare rocks close to shore.
Gulls and terns are the most noticeable inhabitants. While some gulls and common terns nest in small colonies, herring gulls form massive colonies on some of the outer islands such as Gray Island. With thousands of nesting birds per hectare, mass confusion results if a human should intrude. Although gulls are common in Georgian Bay, in many areas of Canada their numbers are low because of high concentrations of pesticides and PCBs. (Polychlorinated biphenols or PCBs are chemicals associated with the manufacture of plastics, lubricants and hundreds of other products which we use every day. While the acceptable level in humans is two parts per million, levels as high as 3 500 ppm have been found in herring gulls of the St. Lawrence River.)
Other birds which breed on the outer islands include yellow warblers, song sparrows and spotted sandpipers.
During spring and autumn migrations, many shorebirds and island-hopping landbirds rest here before or after crossing the Bay. Large rafts of diving ducks and loons seek shelter among these islands. That Georgian Bay is an incredible barrier for migrating songbirds is dramatically illustrated by a storm in 1963 which left thousands of small birds washed up on the southern shores.
Huge sturgeon (up to 2.4 m long and weighing over 68 kg) and lake trout used to be common but are not any longer. The decline of the lake trout may be linked to the accidental introduction of the sea lamprey to the Great Lakes via the St. Lawrence Seaway. The decrease in the number of sturgeon is due to overfishing and destruction of habitat.
Today, in the deep cooler waters there are find whitefish, walleye, white bass, white perch, gizzard shad (a member of the herring family) and muskellunge, a huge member of the pike family which may reach 45 kg. In the shelter of underwater shoals and in rock shallows there are smallmouth bass and rock bass.