Which came first, the sturgeon or the egg?

Freshly fertilized pallid sturgeon eggs in a laboratory environment.

While the Comprehensive Sturgeon Research Project (CSRP) at the USGS Columbia Environmental Research Center (CERC) is focused on pallid sturgeon (Scaphirhynchus albus) and the closely-related shovelnose sturgeon (S. platorynchus), the CERC also conducts behavioral, physiological and toxicological research on other sturgeon species.  Those species include the shortnose sturgeon (Acipenser brevirostrum), lake sturgeon (Acipenser fulvescens), and white sturgeon (Acipenser transmontanus).

Although there are similarities in rearing the various sturgeon species, there are also some differences. Larvae of some species, like pallid and shovelnose sturgeon, move into the water column soon after hatch and may drift with the current for long distances before settling to the bottom and feeding. Larvae of other species, like the lake sturgeon pictured above, do not drift great distances and the young are mottled in appearance to hide from predators as they search for food.

In order to study the early life stages of sturgeon species in the laboratory, it is important to learn how to propagate (breed) and culture (grow) them.  James Candrl, a fish biologist at CERC, has been supporting the CSRP by breeding and caring for sturgeon since 2001.  In the 2011 spring and summer, James raised four different species of sturgeon for studies on diet and starvation, early behavior, and the effects of environmental contaminants on survival and development.  Each of these experiments has one thing in common – the need for live, healthy sturgeon eggs, larvae, and juveniles.  James knows that ”the better you are at propagating and culturing sturgeon, the better your experiment will be.” So, through research and observation, he strives to raise healthy fish, comparable to what might be in the wild.

Click here to view a short video of a pallid sturgeon embryo.  As hatch time nears, sturgeon embryos become more active inside the chorion (egg shell).

Unlike many other fish species, pallid sturgeon eggs and newly hatched larvae are fairly big.  However, because the large and muddy Missouri River is home to the pallid sturgeon, it is difficult to observe these early life stages in the wild.  Therefore, many studies seeking to understand this time in the pallid sturgeon life cycle must be conducted in the laboratory.  Studies that examine early development and behavior provide insight into how far newly hatched sturgeon drift, what habitats are needed when sturgeon begin feeding, what juvenile sturgeon eat, and how long a young sturgeon can go without feeding.  These experiments help predict if they survive in the wild and what may happen if food sources are limiting in the river.

Newly hatched pallid sturgeon larva have a large yolk sac which sustains them until their mouths are fully formed and they are able to feed.

Laboratory studies are very helpful in conducting field work, too.  Research at the CERC helps guide scientists when and where to sample for larval pallid sturgeon, so they may have the greatest success in catching a drifting fish.  In the event that a larval sturgeon is captured in the river, knowledge gained from laboratory studies will help determine how old the fish is as well as when and where its parents spawned.

Scientists track the development and growth of sturgeon embryos and larvae. By knowing the temperature of the water and the developmental stage of the embryo, scientists can predict when it will hatch. This pallid sturgeon is very near hatching indicated by the tail extending to the head and the presence of eyes.

Completed with contributions by Aaron DeLonay and James Candrl.

About Emily Pherigo

Emily is no longer with the Comprehensive Sturgeon Research Project. When she was here, she was a biologist contracted to the Comprehensive Sturgeon Research Project. Most of her time was spent at a computer performing QA/QC on data or updating figures and graphs most used by Aaron DeLonay. However, she occasionally made it to the river, where she enjoyed seeing pallid sturgeon and was reminded why she entered the natural resources field.
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