To launch their armored, prehistoric-looking bodies into the air, Gulf sturgeon have a very specific ritual.
First, they make three clicks by popping their tongue down from the roof of their mouth.
Then, a few thrusts with their tail fin, a “big woosh” of water and they break the surface, said Christiaan Ard, a wildlife photographer who spent his spring filming sturgeon in the Suwannee River.
The fish, which can grow up to 8-feet long and 300 pounds, jump straight up. They twist, wiggle and turn, then flop down with a splash that turns boaters’ heads. One final click ends the sequence.
Gulf sturgeon jump for buoyancy and communication, explained retired fish biologist Ken Sulak. The fish gulp up air as they leap, filling an internal organ that helps them hover just above the bottom of the river and save energy. The series of sounds the feat creates alert other sturgeon to their whereabouts, "like cows in the field mooing,” Sulak said.
Jumping activity soared in the Suwannee River this spring, far beyond what biologists normally observe. Exceptionally low river levels may be to blame, Sulak said, stressing the sturgeon and thwarting their spawning season.
Few probably managed to reproduce, but Sulak isn’t too worried. Gulf sturgeon have made a remarkable recovery in the Suwannee after fishers nearly wiped them out in the 1900s by killing them and harvesting their eggs to be sold as caviar.
As many as 15,000 live in the river today, Sulak estimated, and some have adapted to spawn in the fall, a “safety valve” during unusual years like this one.
True to their name, Gulf sturgeon spend their winters in the Gulf, filling up on food for a long journey ahead.
From January to April, they swim more than 120 miles up the Suwannee River to their spawning grounds around Ellaville, where the Suwannee meets the Withlacoochee River.
“Normally they have no problem getting there,” Sulak said. “But this year we have what's called an exceptional drought.”
After months of below-average rainfall, river levels dropped to near-record lows in parts of the Suwannee River in the spring, blocking sturgeons’ access to the gravel-bottom channels where they lay their eggs.
Trapped and antsy, about 100 to 200 sturgeon packed into a portion of the river spanning less than a square mile, Sulak estimated. The water was low and clear: the total opposite of the dark, deep, cloudy holes sturgeon typically seek.
Jumping activity soared.
Two or three sturgeon sailed through the air each minute, Ard said, far more than what could be explained by a sturgeon’s normal behavior of one jump every two or three days.
“The combination of environmental conditions that they don't like and the frustrated spawning drive probably stressed them to the point that they were jumping a lot more than normal,” Sulak said. “These exceptional situations offer some chances to learn things.”
After about eight weeks of stressed jumping, the sturgeon settled down as summer storms boosted river levels.
Water rose enough by June to let sturgeon through to spawn, but it was too late. The water was too warm for eggs and larvae to survive. A few may have managed to spawn, but most probably failed, Sulak said, and that’s likely okay.
“ Sturgeon as a group have been around for 200 million years, and they've been through two great extinctions,” he said. “They have adapted some options.”
About a fifth of Gulf sturgeon in the Suwannee River spawn in the fall instead of the spring. That helps maintain the species’ genetic diversity and acts as a backup in case drought, pollution or other hazards strike.
Females spawn several million eggs over the course of their lifetime and only need two of those to survive to keep the population stable. “In a good year, when you have lots of survival, it really jumps up the population,” Sulak said.
Paddling the river last week, Ard and Sulak saw far fewer jumps than during their earlier expeditions.
“The fish have probably retreated downriver to their normal summer holding areas,” Sulak said, where they’ll stay until early fall.
Manatee Springs and the Suwannee Belle restaurant are popular spots to watch for jumps.
