The purpose of this study is to better understand the spawning migration and timing of rainbow trout in the spring-fed Fall River of Northern California.  

The spring water's constant year-round flow and temperature are hypothesized to make for an exceptionally long trout-spawning season – October through June. (Rainbows in the more common snowmelt-fed rivers of the American West spawn only during the spring when flows are suitably high and cold.)

In spring and summer 2013, researchers implanted tags into 500 rainbow trout to track their movement throughout the Fall River watershed. Antenna arrays installed near spawning areas will register when and where the trout go to reproduce. Samples will be taken to see if spawning migration and timing influence the genetic makeup of the fish.

A key question is whether some individual rainbow trout spawn during the same period and in the same places, year after year. If so, special conservation considerations may enter into the management of these populations.

California Trout, the project sponsor, produced this video on the research effort.