Wild Side Column: Gulf sturgeon leap in the Suwanee River
I've long been fascinated by sturgeon, ancient fish with armor plating that live in the bottom of large rivers and lakes. Lake sturgeon live in the St. Croix, Chippewa, Flambeau, Bad, Wisconsin, Wolf and Menomonie rivers and in Lakes Superior and Michigan in Wisconsin. A large population of Lake sturgeon lives in the Wolf River system including Lakes Winnebago, Poygan, Winneconnee and Butte des Morts.
Sturgeon spearing through the ice is a popular and highly regulated fishery in on the Wolf River system lakes. Many Lake sturgeon spawn below the dam at Shawano, Wisconsin in mid-April into May, attracting tourists, the DNR, and Sturgeon Patrol volunteers to protect them from poachers and disturbance.
I caught and released four Shovelnose sturgeon, smaller cousins of the Lake sturgeon on the lower Chippewa River last summer above Durand. Like other 27 species of sturgeon world-wide in the family Ascipenseridae (four species may be extinct now), they have a pointy nose that's flat on the bottom, covered with electro-receptors, four barbels ahead of a tube-shaped suction mouth, a cartilaginous skeleton and a shark-like tail. They have five rows of horny scutes that effectively armor them, an evolutionary holdover from their start in the Triassic about 245 million years ago when swimming dinosaurs were predators.
The Suwannee River flows into the Gulf of Mexico about 12 miles north of our winter home in Cedar Key, Florida. The Suwannee remains a fairly wild, undammed river, flowing about 246 miles out of the Okefenokee Swamp in southern Georgia and across northern Florida. The Suwannee River supports one of the largest remaining populations of Gulf sturgeon, a subspecies of the Atlantic sturgeon.
We enjoyed a talk by Dr. Ken Sulak about sturgeon at the Cedar Key Public Library last Saturday. Dr. Sulak is Scientist Emeritus with the U.S. Geological Survey Wetland and Aquatic Research Center in Gainesville, Florida. Dr. Sulak has been studying sturgeons for decades in the U.S., Canada and in Russia. He and his graduate students have studied Gulf sturgeon in the Suwannee River and other rivers since the early 1980s. The Gulf sturgeon is native to rivers from the Suwannee River in Florida to the Pearl River on the Louisiana-Mississippi border.
Like other sturgeons, the Atlantic and Gulf sturgeon are large river fishes that spawn on fast-flowing well-oxygenated gravel and rock bars. Unlike most other sturgeons, they are anadromous, spending the fall, winter and spring months feeding in the shallow Gulf of Mexico. There they feed on abundant macroinvertebrates on the bottom and gain most of their body weight. Starting in May, the sturgeon swim up the rivers to spawn on a few places in the upper Suwannee River where there is fast current and gravel. After spawning they fall back into deep holes and rest there until the fall when they return to the ocean to feed. They don't feed much when in the river and lose a good bit of weight. Young sturgeon stay in the river for several years before the skinny young ones venture into the Gulf, physiologically adapt to saltier water, vacuum up food and grow rapidly.
Gulf sturgeon in the Suwannee River are notorious for leaping. You don't want to get hit by a 6-foot long sturgeon when you are blasting along in a motor boat. A young girl was killed in 2015 from being hit by a sturgeon when out boating on the Suwannee River with her family.
Ken Sulak said that the sturgeon aren't jumping for joy or to terrorize motor boaters. The sturgeon jump to replace air in their swim bladders and maintain their neutral buoyancy. They make clicking noises underwater and the leaping and splashdowns may be a way for them to communicate among one another.
Despite surviving on Earth for millions of years and outliving the dinosaurs, sturgeon are vulnerable to overfishing, dams, and water pollution that degrade their natural habitat. After commercial fishing for sturgeon in Florida was banned in 1984 and the Gulf sturgeon was listed as a federally-listed threatened species in 1991, the Gulf sturgeon population in the Suwannee River has made a good recovery. From very few fish in the early 1980s, the Suwannee River population of Gulf sturgeon may now have around 10,000 adults.
If you go boating on the Suwannee River in the summer, go slow. You might get to see a leaping Gulf sturgeon. If you want a similar experience, float downstream from County H bridge near Caryville on the Chippewa River in western Wisconsin. A couple miles downstream is the deep Sevastopol Pool where paddlefish often leap, doing cartwheels in the air. They are another mysterious ancient big river fish that make a big splash.
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