Good topic.
If I catch on a hookbait I reuse it if it is still usable. It was acceptable at that time to the fish I caught so it should be acceptable to the next fish that find it.
In the Loeb report (scientist testing various substances on blind carp in the 60s) Loeb finds that human saliva and tobacco juice is among the substances found attractive by carp.
Regarding the smell of skin. There has also been some testing on various species with "finger-rinse", water where someone has dipped their fingers. This is from memory acting as a stimulant to some fishes (I believe goldfish was one) and repellent in others (some sort of salmon)
