To spit on the salmon means to suck a dick.
The term comes from norwegian, and is «Spøtte på laksen» in norwegian.
Note! Since salmon is a normal cuisine in Norway it is important to remember to not use the term in a conversation about food.
Did u get some at the party?- friend
Nja, I meet this guy, but I was on my period, so I could only spit on the salmon.-