The last thing you want to do is to sand or take steel wool to it. Clean it with warm soapy water and soft brush, then dry it completly, compressed air works well. Then soak it in mineral oil (drug store), in a small plastic container, over night. Then wipe clean with soft cloth and lots of elbow grease. This should help stop the rust, being a fishing knife it probably has seen some water. Nice knife, what does the tang stamp say? Lastly Welcome to AAPK.
Yes, fish knife. The "saw" blade is a fish scaler and the notch on the end is for removing hooks from the fish's mouth but you probably already knew that.
Forged on the anvil of discipline.
The Few. The Proud.
Jerry D.
This country has become more about sub-groups than about it's unity as a nation.
"The #72 pattern has got to be pretty close to the perfect knife."
--T.J. Murphy 2012