Similar to its Pacific cousins, species of Atlantic Salmon are spawned in gravel beds near the headwaters of streams, swim down to the Atlantic, live there several years growing big, then swim back again to spawn.
Unlike Pacific salmon, however, Atlantic salmon usually survive the experience of returning home to spawn, and swim back down to the ocean, and return to spawn again and again. The difference certainly derives from the more rugged terrain of the West Coast of North America, and thus the greater number of obstacles that Pacific Salmon have to surmount while fulfilling their destiny. It remains to be seen whether death after one spawning is an evolutionary adaptation, or the fish simply hitting physical limitations, being too beaten up after their trip upriver.
Unfortunately for the Atlantic Salmon, their yearly survival makes the entire population more sensitive to overfishing: each Atlantic Salmon caught represents a greater number of potential descendants lost than for a Pacific salmon. Overfishing, coupled with dams blocking spawning routes, pollution of the rivers fish must traverse, and, ironically, diseases and genetic nondiversity brought by escaped farmed salmon, wild Atlantic Salmon reached critically low levels in the 1990's.
The Atlantic Salmon is on the Endangered Species List in the United States, and Canadian salmon fishing is limited to one Inuit community on Ungava Bay. The countries surrounding the North Atlantic (the European Union, Norway, Denmark (thus the Faeroe Islands and Greenland), Iceland, Russia, Canada, and the United States) formed NASCO, the North Atlantic Salmon Conservation Organisation in order to find ways to restore salmon populations. Many activist NGOs (such as the WWF) doubt NASCO's effectiveness, since the EU has not yet limited the salmon fishery in the British Isles.
Membership of NASCO from
http://www.nasco.org.uk
Also see
http://www.asf.ca/Communications/june00/endnasco.html
http://www.asf.ca/Nasco/nasco2001/index.html