Trout in unstocked lakes

Question:

I've found several alpine lakes in the Sawtooths with cutthroat trout yet the lakes do not appear in the F & G stocking reports for any year; they're called "unnamed lake" on the Idaho FishMap and no stocking record is given. In some cases, the lakes are not connected by creeks to any other lakes. Can I assume these lakes were stocked "back in the day" before records were kept and the fishery has reproduced naturally since? Or is there a super-secret stocking report only available to F & G employees (just kidding)?

Some related questions: Are there naturally reproducing populations in the alpine lakes or does stocking produce all sizeable fish? Why were quite a few alpine lakes in the Sawtooths recently switched from stocking of cutthroats to rainbow? I've noticed that rainbows are coming in in some of these lakes but cutthroats are still holding strong in others. Does F & G want observations by fisherman who visit the same lakes every year and notice things about the fishery?

Thanks for this Q & A opportunity and making the Idaho trout fishing so much fun!

Answer:

A number of lakes were stocked many years ago with rainbow and cutthroat trout that established natural reproducing populations.  When we inventory the fish populations in the lakes, if they are being sustained by natural reproduction, we often discontinue stocking or stock less frequently.  Most mountain lake stocking that currently takes place is with sterile fish so we can better control spread and population numbers in the various lakes.

Most mountain lake stocking in Idaho is done by fixed-wing airplane.  There are some lakes that may not have a map name but we have a drainage numbering system and GPS coordinates that remain on our stocking schedule.  Some of these lakes without names may also have been inadvertently stocked prior to GPS technology and a self-sustaining population of fish resulted.

Species of fish stocked in a mountain lake depends on the type of habitat available, the availability of westslope cutthroat, and the preference of our Regional Fisheries Managers.  Over the years, by trial-and-error, we've discovered rainbow trout do better in some lakes than rainbow trout and vise-versa.  We've also made changes based on angler preference, as well.  There are even a number of lakes that receive both rainbow and cuttroat in the same year.  Additionally, there are some years where we don't have enough cutthroat to meet stocking requests so we substitute sterile rainbow trout - just to maintain a fishery in lakes without natural reproduction.

By all means - please send us fishing reports from your mountain lakes fishing trips.  Because of the amount of time required to access the lakes from the ground, our sampling crews visit them once every 10 - 12 years.  Your information if invaluable in helping us make adjustments to our management of mountain lakes fisheries.