The Missouri River is large, muddy, and turbulent. The complexity of the river can make it nearly impossible for scientists to observe the complete pallid sturgeon life cycle in the wild. Therefore, several studies concerning the early developmental stages of pallid sturgeon are conducted in controlled laboratory settings at the Columbia Environmental Research Center (CERC). This summer, biologists began to study what happens to sturgeon embryos after they hatch in the river.
Eggs collected from pallid sturgeon spawned in hatcheries were fertilized and gingerly placed onto an artificial rock substrate. The tiny, three millimeter eggs are very sticky just after fertilization and adhere to the surfaces of the rocks, even in a current (See photo below). The rock substrates with the eggs attached were placed into an artificial laboratory stream that mimicked the conditions where the eggs might develop in the Missouri River. Though the laboratory stream system could not achieve the highest velocities or provide the complexity of hydrologic environments found in the Missouri River, its simple design could provide scientists insight into the mysterious world of the first days of the pallid sturgeon.
After six days of watching the embryos develop and wiggle inside their thin eggshells, the eggs began to hatch. Some of the little sturgeon burst from their eggs head first and disappeared in the blink of an eye–swept away in the current of the artificial stream. Others struggled a bit, emerging tail first and wiggling their way to freedom. Interestingly, most of the freed embryos were rolled off the rocks and into the substrate by the current. Click HERE to view a video of the hatching.
Biologists observed the larval sturgeon and recorded every movement that they made around the clock using infrared digital cameras that can see the tiny fish under water, even in the dark. The young pallid sturgeon developed quickly. After several days their fins began to grow and they were strong enough to orient themselves and swim against the current. In a few more days the larvae began to resemble miniature sturgeon, settled to the bottom of the stream, and moved freely throughout the water in search of food. Biologists measured the changes in development and behavior of the small sturgeon hoping to learn how they have adapted to control their downstream dispersal and eventually end up in places where they can find food and protection from predators. Most young sturgeon do not make it. Only a fraction of one percent of all sturgeon eggs hatch and survive the first year of life. Understanding what young sturgeon do in the first weeks of life may help biologists to find ways to increase their survival just a fraction of a percent more. That little bit more, may make all the difference to sturgeon populations in their dark and mysterious world.
Completed with contributions by Aaron DeLonay, Patty Herman, and Diana Papoulias