I've smoked a lot of fish over the years, lots of salmon for the wife. I can't stand the smell of tuna or salmon!!!!! I've never had any left over smells as long as I clean the grates really good with a stainless wire brush and do a short burn. Ever. I'd have to get rid of the smoker If I ever had left over fish smell.
"Good judgment comes from experience, and a lot of that comes from bad judgment." -- Will Rogers