yes there is, but not on a scale like this... its an organic source, not a chemical source, so over fertilization would be impossible...

and it does fertilize the enitre river, on a small scale... everything goes up and sh!ts that fish crap out, then here in Wa we have this thing called rain, and it rains on hilltops where everything just sh!t on, and that washes down cuz theres another thing called gravity ... not all of it washes down obviously, because its consumed by every organism in the soil, BUT, some does...

leaving the fish on the bank like that im afraid to say, is far better nutrient dispersion wise than letting birds and such eat it, or putting it into a compost pile....

but im still not for it, or feel good when i see it....