We always find difficulty predicting the Arctic spring thaw due to the variability of this environment, but knowing when the Arctic grayling will begin their spawning migrations presents an even greater challenge. In order to raise baby fish in our common garden experiment, we must first capture adults on their way to spawning locations within the newly flowing streams. Ripe with eggs and milt (fish sperm), these adults provide gametes for us to artificially fertilize and raise from eggs to larvae to fry in our local adaptation experiment. Between preparing our common garden aquariums and setting up adult fish monitoring antennas, we also check the river temperatures daily using iButton temperature loggers. I set these tiny loggers to record river temperature at 10 minute intervals to help us gauge when the rivers approach spawning temperatures of 4 to 6 degrees C. Right now, our rivers are still running cold, hovering close to zero, but it won’t be long before the 24 hours of radiant sunshine warm these streams and the grayling leave their overwintering locations en route to spawning grounds. We will only have a small window of opportunity to capture these fish because when the time is right, they move fast. But with a little help from our iButtons, perhaps we can make an educated guess at migration timing and nab them!