Steve Magnelia is the Texas Parks and Wildlife fisheries biologist who heads up the rainbow trout program on the Guadalupe River below Canyon Lake. Water flowing from the deep lake is cool enough that many trout stocked into the river manage to survive the hot Texas summers.

The Guadalupe is the southernmost trout fishery in the U.S. So far, no natural reproduction of the fish has been documented, but that doesn't affect the river's popularity.

The Dallas Morning News caught up with Magnelia on a rainy morning when he and fellow biologist Marcos J. De Jesus were releasing rainbows outfitted with telemetry transmitters, used to track how the fish move through this unusual fishery. Excerpts:

What are you finding about trout movements?

Most of the fish are staying pretty close to where they were stocked. We've only been tracking fish for about two months. We're really interested in where they go when the water starts warming in the summer. Not only does telemetry allow us to track how the fish move, we're also learning some things about mortality. Three of the telemetry fish were caught and kept by anglers. We found one dead from hooking mortality. A few were eaten by cormorants.

How does the Guadalupe trout fishing rate?

In an angler attitude and opinion survey, 90 percent of the respondents said they were moderately to extremely satisfied with their experience on the river. Our best public access site has a catch rate that ranges from .5 to one fish per hour.

What percentage of trout survive the summer?

That's difficult to say because it varies from year to year. Factors include water flow, severity of the summer and an interesting phenomenon with fire ants. If we have a big fire ant hatch, the ants get in the river and the trout eat them. The ants are so toxic that many of the smaller fish die from eating fire ants. Fire ants are not an issue for most trout streams. The river has enough cool springs that we get consistent survival in a normal summer. It helped when GRTU negotiated a minimum flow agreement with the Guadalupe Blanco River Authority that guarantees a river flow, even when the lake is low. That's also helped the local tubing/rafting outfitters.

How many people do you think fish the Guadalupe for trout?

During the 2006-2007 season, a low-flow year when wade fishing was safe and easy, we estimated about 24,500 anglers from Dec. 1 through February. They generated over $500,000 in revenue, and most of them came from outside Comal County.

State record rainbow: 8.24 pounds, 24.5 inches, Joel Starling, Sept. 28, 2001

Fly fishing state record rainbow: 6 pounds, 25 inches, Kyle Kenter, Jan. 26, 2008

Catch-and-release state record rainbow: 24.5 inches, Kyle Kenter, Feb. 4, 2009