Chronology of rainbow trout reproduction in a warmwater tributary of the Chattahoochee River: using an invasive species as an indicator of watershed integrity

The Chattahoochee River near Atlanta, Georgia, USA is a stocked tailwater trout (Salmonidae) fishery and rainbow trout (Oncorhynchus mykiss) have been found to spawn in selected warmwater tributary streams. Because these stocked fish enter non‐stocked waters and produce offspring that reside year‐round, they are technically invasive. One tributary in particular, Cabin Creek, has had documented spawning activity for three consecutive years since the stream was monitored. We chronicled the production of the 2006 year‐class of rainbow trout in this small, warmwater tributary to the Chattahoochee River. Based on electrofishing samples and otolith microstructure, the 2006 year‐class of trout were produced from spawning that occurred from 6 February 2006 to 10 March 2006. Fish from this year‐class grew from an average size of 34.28 mm total length (TL) on 26 April 2007 to 102.00 mm TL on 14 May 2007, which is an average increase in size of 67.72 mm over a 383‐day period or 0.18 mm/day. Water temperatures in the stream were near the lethal limits for rainbow trout, reaching a maximum of 24.57°C on 1 August 2006 and a maximum 7‐day average maximum (M7DAM) of 22.99°C on 7 August 2006. The watershed of Cabin Creek is one of the least urbanized in the area, protected from development within lands owned by the National Park Service, with high levels of forest cover, which facilitates rainbow trout young‐of‐year survival through the summer. Thus, the documented spawning and young‐of‐year survival of this invasive species appears to be indicative of high forested watershed integrity. Copyright © 2008 John Wiley & Sons, Ltd.