The region consists of numerous troughs, basins and shoals, which create a rugged and complex seabed. Depth increases along a general northwest-southeast line through the region, ranging from 100-600 m. Ice cover, which includes both pack ice and landfast ice, is essentially complete for some nine months of the year. Ice edge habitats are critical spring staging areas for seabirds, sea ducks and marine mammals. The coast is dominated by 300-400 m high cliffs, interspersed with coastal plains and lowlands and cut by numerous inlets, bays and spectacular fjords. Permanent ice fields are prominent on the eastern islands and icebergs occasionally break off into the sea from the extensive glaciers reaching the sea. Although some 30 fish species have been reported for Lancaster Sound, one species – Arctic cod – makes up most of the diet of various seabirds and marine mammals.This region also has one of the highest densities of polar bears in the Canadian Arctic. About one-third of Eastern Canada's colonial seabirds breed and feed in Lancaster Sound, including more than 700,000 pairs of thick-billed murres, black-legged kittiwakes and northern fulmars. There are also several thousand pairs of black guillemots, Arctic terns, and glaucous, Iceland and ivory gulls. Large colonies of greater snow geese are located in the region. This region is not yet represented in the national marine conservation areas system. A national marine conservation area proposal for the Lancaster Sound area was prepared in 1987, the area having been recognised early for its tremendous importance within the marine region and the Arctic in general. The feasibility assessment for the proposed new national marine conservation area was suspended at the request of the local Inuit.