That smell would bring back a lot of memories from ny younger days, all-night fishing on the Allegheny in Pittsburgh.
We used to fish in a backwash behind the lock wall on Dam #2. At the end there was a release from the lock, it was about 30 feet deep. Crayfish used to climb up the wall and sit just below the surface, a bit disoriented I think. Anyway, this monster carp used to come up out of the depths and sip the crayfish off the wall. My buddies older brother finally caught him and although I can't remember the exact size he measured well over 50 inches. It took over an hour to land him. He was so big you could almost fit your fist in his mouth.