Fish are aged by reading scales or otoliths. When fish grow they leave rings on their scales much like tree rings. Otoliths are inner ear bones and they are often easier to read then scales. The problem is that to be able to read scales or otoliths you need both experience and a microscope.
If a fish is from a lake that does not have natural reproduction an age can often be guessed based on the stocking records.
Do you have a fish from a particular lake in mind?
North Lake is one I know a bit about. I stock that one myself. It gets fish every 4 years and was last stocked in 1998 and 2002. I really want to get a good survey on North because it will be coming up again next year and I want to be sure we do the right thing.
thanx for replying and telling me how to get to hemple lake McPilchuck. I was looking on my topo map and saw another lake that looks to be decent fishing if there are any fish. Summit Lake is on the south side of pilchick and there looks to be a route from pinnacle lake. Was this lake ever stocked?