Missouri’s landscape has been changing with its growing human population. Our rivers and streams have been channelized (straightened, deepened and reinforced), reducing habitat for the spawning and rearing of some species of fish and other aquatic animals. Some rivers have also been dammed, keeping fish from reaching their historic spawning grounds. Pesticides, fertilizer and erosion have also degraded many of Missouri’s waterways.
Of the 12 federally endangered animal species found in the state, nine live in rivers. These include three fish and six species of native mussels. As steps are taken to stop the decline of these species, the Missouri Department of Conservation’s hatcheries are taking an active role by supplementing existing populations.
Several factors come into play when raising endangered species. The first challenge is obtaining the adults used to produce the offspring. Once the fish are at the hatchery, propagation work begins. Some fish spawn on their own in a hatchery setting, while hatchery staff must inject hormones into other species to induce spawning.
The endangered species raised in Missouri’s fish hatcheries include Topeka shiners and pallid and lake sturgeon. Endangered native mussels, such as pink mucket, fat pocketbook and scaleshell, are also raised.
Topeka shiners are federally endangered and are being produced at the Lost Valley Fish Hatchery. They are a small shiner that reaches a maximum length of 3 inches. They can only be found in two watersheds in Missouri.
The first shiners were taken to Lost Valley in 2000 to begin work on propagation. This was the first attempt at raising the shiners in a hatchery pond, and hatchery staff had to guess at the kind of pond environment they would need for spawning.
For the first three years, 60 to 80 adult shiners were placed in a rearing pond. Creek gravel was provided for them to deposit their eggs on, as they do in their natural environment. The water level and temperature were manipulated to simulate the type of stream pool where they might be found. At the end of the first three years, only a handful of young were raised. Hatchery staff realized that changes needed to be made for the next year.
For the fourth year, 100 shiners were placed in the pond along with nine orangespotted sunfish. The sunfish were added because most of the spawning observed in the wild has taken place at the edges of sunfish nests. It wasn’t long before the shiners were schooled around the sunfish nests, following suit. The end result was that 100 adult shiners produced more than 22,000 young.
Pallid, lake and shovelnose sturgeons are the three types of sturgeon found in Missouri. These fish evolved millions of years ago and were still common in the big river systems only a century ago. The federally endangered pallid sturgeon can live 40 years, weigh up to 65 pounds and attain a length of up to 6 feet. The state-endangered lake sturgeon can live up to 150 years and has the potential to top 300 pounds and reach 8 feet in length. The shovelnose is the smallest of the three and is still abundant.
The Department’s Blind Pony Hatchery, located at Sweet Springs, Mo., is one of only six hatcheries in the U.S. that raises pallid sturgeon. In fact, Blind Pony pioneered the spawning techniques for pallid sturgeon. In 1991, staff used techniques developed for spawning white sturgeon on shovelnose sturgeon. After success with the shovelnose sturgeon, Blind Pony started with pallid sturgeon in 1992.
The hunt for pallid sturgeon adults to serve as brood stock begins in March by biologists on the Missouri and Mississippi rivers. These fish are so rare that finding mature adults can be a problem. The males become mature at 5 to 7 years of age and the females at 12 to 15 years of age. Once the fish are captured, they are transported to Blind Pony.
Once the fish are brought into the hatchery for spawning, the adults are injected with a hormone. Approximately 15 hours after the injections, the fish are ready to spawn. The milt from the males is collected and stored in sterile, refrigerated containers until it is needed. The eggs from the females are collected by applying gentle pressure to the fish’s abdomen, causing the eggs to flow out of the fish and into a collecting bowl.
Once the eggs are collected (up to 100,000 out of a single fish) they are fertilized with the milt. After fertilization, the eggs are incubated in hatching jars. Incubation takes approximately six to eight days depending on the water temperature.
The newly hatched fish (fry) are placed in hatchery tanks for rearing to the stocking size of 9 inches or larger. Throughout their time at the hatchery, the fish are fed a diet of frozen brine shrimp. By October, these fish are large enough to be tagged and released into the Missouri and Mississippi river systems.
A total of four pallid sturgeon females have been spawned in two production years (1992 and 1997) at Blind Pony. Approximately 10,000 9-inch fingerlings were released back into the Missouri and Mississippi river systems from these four females. Blind Pony hatchery is currently being renovated to include a new sturgeon-rearing facility capable of raising up to 14,000 pallid sturgeons each year.
Blind Pony also raises the state-endangered lake sturgeon. However, the lake sturgeon are not spawned at the facility. Instead, the hatchery receives fertilized eggs from the state of Wisconsin. After the eggs are hatched, they are raised with the same techniques used for the pallid sturgeon. All of the lake sturgeon are tagged before release into the Missouri and Mississippi river systems.
Sampling efforts are now underway on the big rivers. These hatchery-produced fish are beginning to show up in fair numbers, and they are proving that efforts to reintroduce the two species of sturgeon are having an effect on the population.
It may be surprising to learn that most of the endangered species found in Missouri rivers are native mussels. Most mussel larvae are parasites of particular species of fish, which means that they cannot reproduce unless that fish species is present. Fortunately, this includes species such as bass and walleye that are produced routinely at hatcheries.
Since 1999, several mussel species have been raised through a combined effort between the state’s hatcheries, including Lost Valley and Chesapeake Hatcheries, and Missouri State University. The federally listed pink mucket, fat pocketbook and scaleshell are among several species being propagated and released. So far, over two million juvenile mussels have been released.
The requirements for successful mussel rearing include gravid female mussels (ones carrying larvae), suitable host fish and the proper equipment to hold the host fish and capture the juvenile mussels. The search for gravid females starts in early spring and continues into late summer.
Once the mussel and host fish are ready, the inoculation process takes place. The valves, or shell, of the female mussel are spread apart far enough to access the gills where the glochidia (mussel larvae) are held. A syringe is used to flush the gills and release the glochidia into a holding container. These larvae only range in size from 0.08 to 0.35 millimeters, so samples have to be counted with a microscope. The number collected from the mussel can range from a few thousand to several million, depending on the type of mussel.
The host fish are then placed in a tub or small tank with aeration (to keep the water oxygenated and the glochidia suspended). The larvae then clamp down on the gills of the host fish. Ideally, up to 300 will attach. This number is small enough not to cause the fish too much stress. The inoculated fish are held in either a recirculating tank or flow-through tank depending on the host fish used.
When the glochidia become attached, they begin metamorphosing into juvenile mussels. Once they have developed into a juvenile mussel, they release from the fish and are collected from the holding tanks by siphoning the water from the bottom and sifting it through small filters. About three days after the first mussel has released, all the mussels will have dropped off of the fish and will be stocked into their natural habitat. Because the host fish develops a resistance to glochidia, they are not used again and are released.
As Missouri’s human population grows, continued changes to aquatic habitat can be expected. While protecting good habitat and restoring damaged habitat is the key to long-term survival of native species, efforts by Department hatcheries will hopefully “buy some time” for endangered fish and mussels, ensuring that they survive these changes.
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Become a vital part of one of the nation’s most respected conservation departments—an agency dedicated to managing Missouri’s fish, forest and wildlife resources.
Know that your work makes a difference for Missouri’s people and nature—today and for the future.
Contact your local conservation facility or visit missouriconservation.org/volunteer to find a volunteer opportunity that’s a good match for your outdoor passion and skills. See page 1 for a list of regional phone numbers.
1401 N.W. Park Road, Blue Springs, MO 64015
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(816) 228-3766; missouriconservation.org/areas/cnc/burroak/
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