Lake Sturgeon, Acipenser fulvescens
Lake sturgeon, Acipenser fulvescens, are a temperate fish occurring in freshwater systems of North America from the Hudson Bay through the Mississippi River drainages. This sturgeon prefers sand or gravel habitat on the bottom on a riverbed or lake. Lake sturgeon populations are declining throughout the species’ native range and are listed as threatened in 19 out of the 20 states it inhabits. There are several reasons for this decline including over-harvest and habitat loss due to dam construction.
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The lake sturgeon is a docile fish despite its intimidating look and size. This species can grow to nine-feet in length and weigh more than 300 pounds! Like its prehistoric ancestors, lake sturgeon have a distinct shark-like tail and rows of armored plates called “scutes” for protection. This fish’s skeleton consists of bone and cartilage.
Lake sturgeon spend most of its time grubbing on the lake or river bottom for food. This species does not have teeth but have a small mouth with thick, sucking lips beneath the projecting snout. Lake sturgeon have four barbells (whiskers) in front of the mouth that are used to detect food like insects, worms, snails, crayfish, small fishes and other organisms. As soon as the sensitive whickers pass over food, the protrusible mouth drops down with an elevator-like motion and rapidly sucks in its meal.
Lake sturgeon are slow moving fish but will migrate up rivers during spawning season. Female sturgeons generally reproduce between the ages of 20 and 26 years old. Males usually mature between 8 and 12 years old. While the male sturgeon’s typical life span is 50 to 60 years, the female sturgeon can live up to 150 years!
Warm Springs NFH’s Involvement
Warm Springs National Fish Hatchery has been rearing lake sturgeon since 2000 in an effort to reintroduce lake sturgeon in two areas where the species was previously found. The hatchery works closely with the Tennessee Wildlife Resource Agency, Georgia Department of Natural Resources, and Wisconsin Department of Natural Resources and reintroduction efforts are concentrated in the Lower French Broad River in Tennessee and the Coosa River in Georgia.
Warm Springs National Fish Hatchery staff travel every year to collect eggs from lake sturgeon caught in the Wolf River, Shawano, WI. Eggs from a minimum of five females are crossed with sperm collected from at least thirty males. These pairings ensure up to 25 family groups will be produced each year, which will assist in maximizing the genetic diversity of the founding population. The hatchery partners with the Wisconsin Department of Natural Resources to collect broodfish for pairings. Wisconsin DNR staff collect male and female lake sturgeon from the riverbank using a large dip net. Length, weight, sex, tissue (fin clip about the size of a pencil eraser), and other data are collected from each fish. When a ripe female is sampled, eggs will be collected by massaging the female’s abdomen. The eggs are divided into five groups and each group is fertilized with sperm from one male. After fertilization, the eggs are rinsed and a mixture of Fuller’s earth is added to de-adhese the eggs.
Fertilized eggs are transported directly from the Wolf River collecting site to Warm Spring’s hatchery in a trailer that is equipped with a tank, hatching jars, water pump, cooling unit, oxygen, and generator. During transportation, the eggs receive a constant flow of 15°C oxygenated freshwater and tumble gently in hatching jars to avoid clumping (the eggs are extremely sticky).
After arriving at the Warm Springs National Fish Hatchery, eggs are disinfected with 100 ppm iodine, measured volumetrically, and placed into the hatching jar system until they hatch. It can take approximately 4 to 8 days for the eggs to hatch. During the first 30 days of culture, fish are quarantined in a re-circulation system with approximately 1.5% water exchange per hour at 15°C.
By mid-June, lake sturgeon have grown to approximately 1 to 1.5 inches in length. At this size, the fish need more room to grow and are distributed to different hatcheries: Warm Springs National Fish Hatchery, Warm Springs, GA; Private John Allen National Fish Hatchery in Tupelo, MS; Mammoth Spring National Fish Hatchery in Mammoth Spring, AR; Orangeburg National Fish Hatchery in Orangeburg, SC; and the Tennessee Aquarium Research Institute’s Hatchery in Cohutta, GA. The sturgeon are reared in these five facilities until October-November and have grown to 6-12 inches in length. At this time, lake sturgeon are graded, marked, and stocked into the French Broad, Holston, and Cumberland rivers.
The hatchery prepares to release lake sturgeon when a batch reaches stockable size. It can take several days to prepare the batch of fish for its final destinations – rivers located in within their native range. The stockable size for this species of sturgeon is usually six inches, and this is predetermined by the lake sturgeon management plans. The hatchery’s first stocking is approximately 1,000 fish that have reached stockable size. Fish size is important to ensure the fish can survive the tagging procedure and stocking bigger fish into a river will hopefully reduce predation.
The first step in the process is to grade fish or sort according to size. The largest fish are moved into two 20-foot raceways. Smaller fish are reared in 8-foot tanks. Once a tank holds 6 inch or larger fish, it is time to set-up the marking/tagging equipment. This set-up period can take two days.
On the third day, biologists and volunteers are recruited to help mark the lake sturgeon. The actual marking process is rather simple but can be time consuming. To start marking, hatchery manager, Carlos Echevarria, will collect about 25 sturgeon from one of the raceways using a net and place the fish in a large tub filled with water, air, and anesthetic. Once the sturgeon have become lethargic, the fish are moved to a second tub to measure length and weight. A biologist will take one fish and put it on a measuring board and scale to record length in millimeters and weight in grams. These measurements are taken for about 5% of the total number of fish to be stocked and an average length and weight is then calculated for this particular stocking. For example, if 1200 fish are stocked, a sub-sample of 60 fish will be measured.
After measuring the sub-sample, the lake sturgeon are moved to another tub for marking. Each biologist and volunteer will don a pair of gloves, pick up a fish, and mark it. Marking requires the removal of one or two scutes using a curved scalpel. Scutes are removed in a certain pattern each year. This pattern helps to determine the year-class of fish that are recaptured from the wild. Based on recapture rates of each year-class, the lake sturgeon stocking success can be determined.
The sturgeon are placed into a freshwater recovery bin after the scutes are removed. Fish will recover from the anesthetic in just a few minutes. This process is completed as quickly as possible to reduce fish stress. Fish are returned to the raceway after recovery. It takes a few hours to get 1,000 lake sturgeon marked, and with the help of the volunteers, fish marking is completed before lunchtime.
On the fourth day, the lake sturgeon are hauled to stocking locations. Before the fish are stocked, a hauling tank on a truck is filled with water. Fish are netted from raceways and placed into hauling tank. Oxygen is turned on after fish are placed in tank. Hatchery worker, Chad Shirey, then drives the distribution truck to the stocking locations. It takes several hours to drive to the stocking site, so hatchery staff get an early start. Chad will drive to middle Tennessee to stock the fish. He is met by Ed Scott, Tennessee Wildlife Resources Agency, at the stocking location’s boat ramp. The two will back the hauling tank to the river and begin to pump water from the river into the tank. This will temper the fish to the river water. This critical step is important and ensures fish will not be shocked by just stocking directly into river. Fish will be tempered for approximately an hour and then Chad will open the hatch and release fish into the river.
For more information about the lake sturgeon program, please contact Carlos Echevarria at 706-655-3382 ext. 1224 or firstname.lastname@example.org.