The Canadian actress and spokeswoman for People for the Ethical Treatment of Animals dropped the letter to Prime Minister Stephen Harper in a mailbox in front of the Canadian Department of Fisheries and Oceans office.
Anderson called the hunt "an embarrassment to Canada" at a news conference, saying she made the appeal during the Winter Olympic Games here because "the whole world is watching Canada."
Canada's annual East Coast seal hunt from mid-November to mid-May, mostly in Newfoundland and Labrador and in the Gulf of St. Lawrence, is the largest in the world,killing an average of 275,000 harp seals.
The hunt has long been controversial. Animal rights groups believe it is cruel, poorly monitored and provides little economic benefit. Seal hunters and Canadian authorities say it is sustainable, humane and provides income for isolated communities.
Anderson said in her letter that there is little ice in the Gulf of St. Lawrence for the seal birthing season.
"The absence of this birthing habitat will have dangerous consequences for the entire harp-seal population. Without ice, mother seals will be forced to abort their pups in the water," Anderson said in the letter, which included signatures from more than 50,000 people who want the annual hunt to end permanently.
Fisheries and Oceans officials confirmed there is very little ice in the Gulf of St. Lawrence and off the eastern coast of Newfoundland and southern Labrador.
"Similar circumstances in the past have resulted in higher than normal pup mortality," said department spokesman Alain Belle-Isle.
Belle-Isle said poor ice conditions in the traditional birthing locations could result in a movement of pregnant seals to nontraditional areas farther north.
"It is unknown if this would result in increased mortality of young," said Belle-Isle.
Canadian scientists use information on pup mortality resulting from poor ice conditions in their management of the harp seal population.
There are an estimated 6.8 million harp seals in the Gulf of St. Lawrence and eastern Newfoundland and Labrador, the Fisheries and Oceans department said.
The European Union has banned imports of all products and processed goods derived from seals, including their skins — which are used to make fur coats, bags and adorn clothing — as well as meat, oil blubber, organs and seal oil, which is used in some omega-3 pills.
It exempts products derived from traditional hunts carried out by Inuit in Canada's Arctic, as well as those from Greenland, Alaska and Russia.
Anderson's plea may fall on deaf ears after Harper and his cabinet dined on seal last August in support of the industry.