Shortnose Sturgeon - Acipenser brevirostrum
By Sara K. Green, SCWF Director of Education
Sturgeons are an ancient species of fish with fossils dating back 65 million years. The Shortnose sturgeon can be found in the salt or brackish coastal waters of South Carolina. It looks like a prehistoric cross between a shark and a catfish. The Shortnose is dark above and light below. (This is a common color pattern for fish, called countershading - when predators look at the sturgeon from above, it blends in with the dark color of the substrate on the bottom. When seen from below, the sturgeon blends in with the lighter color of the water and sky above.) Shortnose sturgeon are usually less than 3 feet in length, which is small compared to their larger, better known cousin, the Atlantic sturgeon. The Shortnose has no teeth in its wide mouth that is pointed downward beneath a short snout. They feed on bottom-dwelling invertebrates and plant matter embedded in the bottom mud. They find this food with their soft, fleshy barbs which cause some folks to mistake these rarely seen creatures for a kind of catfish. Shortnose sturgeons lack scales but have a unique body armor of diamond-shaped bony plates called scutes. Some sturgeons have been found to be over 60 years old.
From April to early June, Shortnose sturgeon migrate from the ocean to large tidal rivers specifically to reproduce. They do not build nests, but rather broadcast their eggs into the water in areas with gravely, rubble substrates. The eggs are small, dark brown, and less numerous per pound of fish than other sturgeons. Once hatched, the young fish drift downstream and may eventually swim to brackish water. The young are rarely seen, so early life history is unknown. Male Shortnose sturgeon mature at an age of four years after reaching a size of 20 inches, females mature after five years at a size of 24 inches.
The Shortnose sturgeon is listed as a Federal Endangered Species. A severe decrease in populations has been documented and is attributed primarily to over-harvesting in the 1800’s and early 1900’s. Sturgeons were harvested for their meat, skin, swim bladders, and eggs (or roe). Shortnose taken commercially in more recent years are often bycatch - accidentally caught by fishermen who are looking for the larger Atlantic sturgeon. Along with exploitation by commercial fishermen, pollution of tidal streams and estuaries used by spawning adults and as nursery areas for young is considered another primary reason for the great decline in Shortnose sturgeon. Dams also contribute to the problem, since they prevent the adults from returning to fresh water to spawn, and the juveniles from migrating from the nursery area out to sea.
The Shortnose is a Federal trust fish, meaning that the Federal government has some responsibility for its recovery. Current research on the behavior of these fish is providing valuable information for the development of management strategies. According to Mark Collins of the Marine Resources Research Institute, the SC Department of Natural Resources has conducted studies on bycatch mortality in the commercial shad gillnet fishery, hatchery and culture techniques, trial stock enhancement, and radio and acoustic telemetry studies of adults and juveniles to determine habitat use and movements. They are also studying juvenile Shortnose sturgeon in the Savannah Harbor to determine the impact that harbor dredging and deepening will have on this species. Deepening the harbor would result in an increase in the salinity and a decrease in the amount of dissolved oxygen in the water. These dramatic changes can have drastic effects on aquatic species.
Management strategies for Shortnose sturgeon that are currently in use include taking inventory and modeling the dynamics of natural populations, enforcement of existing environmental regulations concerning pollution, creation of new regulations, and studies of shortnose sturgeon’s environmental needs and limiting factors. Mr. Collins says that there are some waterways in South Carolina that the DNR has no information about in regards to shortnose sturgeon populations, due to lack of funding. With no research being done in these areas, it is very difficult to determine the effect that management practices are having on the population. Mr. Collins expresses his concern that most of the money that has been earmarked by the National Marine Fisheries Service for endangered species goes to the more “popular” species, such as sea turtles and marine mammals.