Study Spotlight: Robust Redhorse in the Savannah River

Robust Redhorse in Hand

Photos: Alan Cressler

Georgia DNR biologists work hard every day to make the best decisions for the citizens of Georgia and the management of our wildlife resources. This often requires extensive research studies to make well informed decisions for the future.

What is a Robust Redhorse anyway?Robust Redhorse Before Implant

Robust Redhorse are a species of suckerfish thought to be extinct until rediscovered by Georgia wildlife biologists in 1991. They are the largest species of suckers in the Southeastern U.S and can be found in the Altamaha River system east to the Pee Dee-Yadkin system in North Carolina. The Robust Redhorse is currently state listed as endangered in Georgia and the Carolinas. This designation protects it throughout its range.

Why do we care about a suckerfish?

They aren’t currently listed under the U.S Endangered Species Act but are still considered an “at risk” species. Biologists still want to keep a close eye on their populations and created a Candidate Conservation Agreement. This agreement allows multiple agencies to work together to ensure the long-term survival of a species without listing them under federal law. As a result, the Robust Redhorse Conservation Committee was born.

Why are we studying this and why is it important?Capture Group

The main things biologists want to determine are:

  1. Which river reaches are seasonally important habitat?
  2. What environmental factors like flow or temperature in the Savannah River trigger spawning migrations? 
  3. Do spawning migrations happen at the time same across different ages and sexes and how long do they stay at the spawning grounds?

Answering these questions and gaining more information about how Robust Redhorse use the Savannah River will help future management of the species and river.

Where is this study happening?

The Savannah River in Georgia and South Carolina.

How long is the study going on?Catching Robust Redhorse

The study is brand new and began in May 2018. Biologists will continue to gather data for next 8–10 years, depending on the life of the transmitter tag and fish.

Who's answering the questions?

Members of the Robust Redhorse Conservation Committee! Georgia DNR biologists, GA Power ecologists, and Georgia Southern University professors and students will work together with sampling events and managing data.

How does the study happen?

Biologists wanted to take advantage of the Savannah River’s stationary acoustic receivers that are already being used to monitor sturgeon, striped bass, and other species of concern. So, eleven Robust Redhorse had transmitter tags implanted into them that send off a sonic “ping”. If the fish swims by a receiver and hangs out long enough for the receiver to pick up two consecutive pings, then the fish’s tag number is recorded by the receiver. During spawning season they’ll also track tagged fish with a mobile unit in order to see if they are moving between spawning grounds. The majority of the fish captured this year were males. Nine more transmitters will be implanted next year to ensure that enough data is collected from each gender.

Does the implant hurt the fish?Robust Redhorse Tagging

No. The University of Georgia Veterinary College came along during the tagging event by performing on-site surgeries to implant the transmitters into the fish. This ensured that the collected fish received the highest level of humane care and maximized the probability of tag retention. After implantation, the tag causes no harm to the fish.

How long until we know something?

Likely in June or July. Biologists should start receiving early data as soon as the fish leave the spawning bar to head back downstream and pass the stationary receivers along the way. Unfortunately, the fish can’t be tracked in “real-time,” but we will receive monthly and quarterly updates.