NANFA-- salmon carcass nutrients article

Jay DeLong (
Fri, 26 Jan 2001 20:37:29 -0800

The Jan 2001 Fisheries magazine has an interesting article. (It's probably
on their website but I haven't checked.) The authors suggest a way to
determine minimum numbers of adult salmon to allow to return to streams by
using a new technique based upon nutrient input to the watershed. The
importance of carcasses as a vehicle for marine nutrients to get into
freshwater has been known for some time, but has only recently become
popular. And now there seems to be a quantitative way to measure
this. Apparently there is an isotope of Nitrogen which is marine-based,
and researchers can sample freshwater organisms like salmon fry and
estimate how much of their Nitrogen originated from marine waters (salmon

My question is: Why is there an isotope of Nitrogen (N-15) found in oceans
and not in freshwater? The authors stated it as a matter of fact, but I'd
like to know more. Thanks.

Jay DeLong
Olympia, WA

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