Brown Trout Reproducing, Surviving In Atlanta’s Chattahoochee River

Each spring and fall a team of WRD biologists conducts an electrofishing survey of the brown-trout population on the Chattahoochee River below Buford Dam.

I had the opportunity to be aboard the shocking boat during the fall survey in 2009 to observe the action. I met WRD Region Supervisor Chris Martin at Settles Bridge on a cold morning in late October. Martin maneuvered the jet boat into the shoals upstream of the bridge and turned on the generator. With electrodes in the water on booms in front of the boat, he guided the boat through the shoals. It didn’t take long for trout to start coming to the surface, lots of them. In a few minutes, Martin and his associate had netted what looked to be a couple hundred trout. All but a handful were browns, and they put them in an aerated livewell. And I’ll bet they didn’t capture 25 percent of the fish that surfaced from being stunned.

Then the real work began. Each trout had to be weighed, measured and recorded. That took much longer than capturing the fish.

In the spring survey, usually in April, a similar sampling is done. During that survey the focus is on “young of year,” which is the small fish that hatched in the spawn during the late fall and early winter. Martin explained that the young of year is a good measure of how natural reproduction is progressing in the river, as well as fry survival rate.

“Our data shows that 2008 and 2009 had the highest young-of-year counts recorded to date,” said Martin. “So clearly the natural reproduction is going well.”

In addition, the fall sampling catch-rate-per-hour has increased significantly over the last few years. In 2004, when the last browns were stocked, the rate was 165 fish per hour. In 2009, that rate increased to 365 per hour.

Martin feels that both the spring and fall 2010 data may be down due to the heavy rains and large water releases from the dam causing extremely high river levels and current flow during the brown-trout spawning period in November and December. The eggs and fry may have been literally washed downstream.

While brown trout have adapted to the river nicely and are maintaining the population on their own, that is not the case for the rainbows.

“The rainbow-trout fishery is supported almost completely by stocking,” said Martin. “We have observed and recorded evidence of some natural reproduction by rainbows but in very small amounts.”

Martin said most of the rainbow spawning activity has been observed below the Morgan Falls Dam.

According to Martin, the brown trout tend to be more prolific and larger as you move downstream from the Morgan Falls Dam. The river near the outflow from the lake is not very fertile and doesn’t support much in the way of food for the trout. Further downstream aquatic and terrestrial forage is more prevalent and the trout fare better.

One thing is certain: There are plenty of brown trout surviving naturally in the Chattahoochee below Lake Lanier. That makes the river one of the better wild trout streams in the state.