... log books and thermometers are aids to some anglers in some places. Those places probably constitute a small segment of a trout angler's huge universe.

A log book doesn't exist for your first time on new water ( and, personally, that is my favorite kind of place in our huge universe ). Understanding trout and their needs and good fly selection and presentation skills are about all that count.

Some of the big freestone rivers in the Intermountain West change so much each year that anything you experienced last year is old news and of no value. The same can be said of a lot of the smaller streams that have significant runoff. Again, understanding trout and their needs and good fly selection and presentation skills are about all that count.

How about fishing the duration of a huge runoff like we had in the West this year ?? Conditions change daily and the fish are adapting and moving regularly. What you did yesterday is of no consequence.

Like virtually everything in fly anglings - it depends. If you fish the same creeks every year and they never change, or see minimal structural change, year to year, log books and thermometers have a place.

If you fish rivers like the South Fork of the Snake or the Bitterroot or creeks like Big Elk, to name just a few examples of the hundreds of trout streams out here, or take on the challenge of new water regularly, forget the log book and learn about trouts and their prey.

John