Darn right they are. The several species of Pacific salmon have evolved
methods to partition the shared habitat in space and time. The only
multiple spawner, Onchorhynchus mykiss (steelhead), is a winter/spring
spawner, chinook spawn early and their fry leave freshwater in early
summer, while other species spawn later and their fry either leave
freshwater very early in the year (chum, pink) or stay through their first
summer (coho). Sockeyes require a lake for rearing, reducing the overlap
of habitat. It really shouldn't come as a great surprise that these species
coexist because they evolved together.
Enter Atlantic salmon-- fall spawners like Pacific salmon, multiple
spawners like steelhead, and they stay in freshwater 2-3 years before
entering saltwater. I don't know what if any negative effects may come
from their ability to spawn over multiple years, but their 2-3 year
freshwater life history means they're competing all summer with coho fry
(typically times of reduced resources-- water, food), and when the fry of
all the Pacific salmon species hatch and emerge in late winter, they're
greeted by those bullies from the Atlantic. I don't think Atlantics eat
fish fry, but they're there in several age classes competing directly with
native salmon fry.
-- Jay DeLong Olympia, WA /----------------------------------------------------------------------------- /"Unless stated otherwise, comments made on this list do not necessarily / reflect the beliefs or goals of the North American Native Fishes / Association" / This is the discussion list of the North American Native Fishes Association / nanfa_at_aquaria.net. To subscribe, unsubscribe, or get help, send the word / subscribe, unsubscribe, or help in the body (not subject) of an email to / nanfa-request_at_aquaria.net. For a digest version, send the command to / nanfa-digest-request_at_aquaria.net instead. / For more information about NANFA, visit our web page, http://www.nanfa.org </x-flowed>