Scaphirhynchus platorynchus

Geographic Range

Shovelnose sturgeons are a freshwater species historically found in most portions of the Mississippi and Missouri river basins. This area ranges from Montana south to Louisiana, and from Pennsylvania west to New Mexico. However, shovelnose sturgeons are no longer found in Pennsylvania, New Mexico, and large parts of Kansas, Kentucky, and Tennessee where they were once abundant. The main cause for the restriction of range is the construction of dams on many of their native waterways.

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Shovelnose sturgeons are primarily bottom dwellers, preferring high turbidity in large waters, and are usually found in pools downstream of sandbars or along the main channel border. The flowing freshwater is between 18-20 deg C. During low water or in the warm summer months, these sturgeons seek cooler, deep channel areas.

• Habitat Regions
• temperate temperate
• freshwater freshwater

• Aquatic Biomes
• benthic benthic
• rivers and streams

Physical Description

Shovelnose sturgeons have an elongated body with five rows of sharply keeled body plates: 14-19 dorsal plates, 38-47 lateral, 10-14 ventrolateral. They are olive to yellowish-brown in color on the top with lighter sides, and white on the bottom. The head contains bony plates with short spines at the tip of the snout and anterior to the eye. The snout is rounded and pointed up. The caudal peduncle is long, depressed, and fully armored. The tail is heterocercal, with the upper lobe containing long, thread-like filaments. All four barbels are evenly spaced under the jaw, unlike the related pallid sturgeon , which has barbels unevenly spaced under the jaw. The most readily distinguishing characteristic of the shovelnose is its small size and dark color. They rarely exceed 5 lbs (2.3 kg) or over 28 inches (70 cm)in length.

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• female larger

Development

Eggs are deposited over cobble, gravel, or rock, becoming adhesive and attaching to the bottom substrates. After five to eight days, the eggs hatch and the young begin to search for food on the river bottom. Females grow significantly faster than males.

• Development - Life Cycle
• indeterminate growth indeterminate growth

Reproduction

Shovelnose sturgeons migrate upstream, sometimes as far as 540 km if unimpeded, in a search for acceptable reproduction habitat and mates. Due to proximate cues, such as day length, water flow, and water temperature, all adults of reproducing age gather at spawning sites in large numbers. Although these fish are usually bottom dwellers, they rise to the surface during this time. Commonly, the same sites are used for spawning over the years. Once at the spawning area, mating begins, and fertilization of eggs occurs.

Not all females spawn every year. The frequency is determined by food supply and ability to store adequate fat to produce mature gametes. Males however, always spawn if physically possible.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

Breeding begins when females are around seven years of age and the males are approximately five. Mature shovelnose sturgeons travel upstream to spawn over rocky substrates in flowing water between 17-21 deg C, usually downstream from a dam in April to early July. The male and female swim side by side while they release eggs and sperm. Once the eggs are fertilized, they adhere to the rocky substrates. It is very important that there is a continuous stream of water flowing over them, and that the substrate is not too fine, so that it does not settle over the eggs and suffocate them. After 5 to 8 days the dark gray eggs, measuring 2 to 3 mm in diameter, hatch. Within approximately three months, when the young are 15 to 20 cm, they are independent, and leave their natal habitat.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• fertilization fertilization
  • external external
• broadcast (group) spawning
• oviparous oviparous

These sturgeons have to use a great deal of energy to swim upstream for long distances to spawning areas. Once at the spawning areas, and fertilization of eggs has occurred the female deposits approximately 50,000 eggs per spawning season. The parental involvement is very limited after eggs have been deposited. Both male and female return downstream to their original home range, leaving un-hatched eggs attached to bottom substrates at spawning areas to develop independently.

• Parental Investment
• pre-fertilization
  • provisioning
• pre-hatching/birth
  • provisioning
    • female

Lifespan/Longevity

The largest shovelnose sturgeon recorded weighed 13.72 lbs (6.2 kg). Most are not expected to live over 30 years of age.

Behavior

Eggs are deposited on rocky substrates, providing protection for young shovelnose sturgeons to develop in safety. As the young mature they begin to travel greater distances away from their natal habitat. Females grow significantly faster than males, enabling them to travel further earlier. These fish spend their lives swimming near the bottom over cobble or gravel substrates in fast, turbid water, feeding mostly on invertebrates.

The behavior of S. platorynchus is highly adapted for life in the current. They spend most of their lives, except during spawning, on the river bottom in deep, cool channels. The current makes it easier to find food, and their specialized siphon-like mouths act like vacuums, sucking up organisms buried in the benthic substrates. They have a wide home range, and can travel large distances in one day searching for food. Increased water flow seems to trigger the behavior to move upstream. Usually they are not found in large groups, except during breeding.

• Key Behaviors
• natatorial natatorial
• diurnal diurnal
• motile motile
• sedentary sedentary
• solitary solitary
• social social

Home Range

The shovelnose sturgeon can travel up to 20 km in one day, however, most patrol a much smaller range in the search for food. Home range is not set for their entire lifetime, and can change as food abundance or alteration in habitat occurs.

Communication and Perception

Shovelnose sturgeons search for food by manipulating their large barbels which have taste buds and electrorecptors. These barbels hang below the mouth and feel the bottom as the sturgeon swims. This allows them to sense when food or other obstacles are below.

• Communication Channels
• tactile tactile

• Perception Channels
• tactile tactile
• chemical chemical

Food Habits

Scaphirhynchus platorynchus are opportunistic feeders, eating mostly aquatic insects, mussels, worms and crustaceans. Altered stream flow can affect the sturgeon’s ability to find food and also influences the abundance of prey organisms. The barbels detect prey, and then the sucker type mouth easily picks up the food organisms. Most food is found over sand and gravel substrates.

• Primary Diet
• carnivore carnivore
  • insectivore insectivore
  • eats non-insect arthropods
  • molluscivore molluscivore
  • vermivore

• Animal Foods
• insects
• mollusks
• terrestrial worms
• aquatic or marine worms

• Foraging Behavior
• filter-feeding filter-feeding

Predation

Other fishes, such as catfishes and burbots, probably eat the young shovelnose sturgeons. The main predator of adult shovelnose sturgeons is man. Presently, about 25 tons of shovelnose sturgeon are harvested annually. Sixty percent come from the Mississippi River upstream of St. Louis, Missouri. They are harvested in late fall and early winter for both meat and highly valued roe. The alteration of large rivers, and construction of locks and dams for navigational purposes has contributed significantly to the decline of the species by blocking access to ancestral spawning grounds, and by eliminating its required habitat.

Ecosystem Roles

Scaphirhynchus platorynchus feed on invertebrates, stirring up and loosening bottom substrates. The shovelnose sturgeon harbors a newly discovered virus called the Missouri River Sturgeon Iridovirus or MRSIV. The shovelnose sturgeon is host to the hickory-nut Obovaria olivaria , and may possibly be hosts for other pearly mussels including commercial species. Lamprey also parasitize the fish.

Economic Importance for Humans: Positive

Shovelnose sturgeons have many benefits to humans. They have been commercially harvested since 1987, and the meat is considered a delicacy, especially when smoked. They are also considered a sport fish in 12 of the 24 states in which they occur. The roe is used as an acceptable caviar and it has also been introduced as a potential aquarium fish.

• Positive Impacts
• pet trade pet trade
• food food

Economic Importance for Humans: Negative

There are no known adverse affects of shovelnose sturgeons on humans.

Conservation Status

Shovelnose sturgeons are considered extirpated in three states, fully protected in four, and rare, or of special concern in eight states as of 1996. However, they are not currently listed as federally threatened or endangered.

Other Comments

Rafinesque described this species as the 97th species described in his book, "Ichthyologia Ohiensis: Natural History of the Fishes Inhabiting the River Ohio and Its Tributary Streams," published in 1820.

Additional Links

Encyclopedia of Life

Contributors

Katie Lord (author), University of Michigan-Ann Arbor, William Fink (editor, instructor), University of Michigan-Ann Arbor, Renee Sherman Mulcrone (editor).

References

Bradshaw, R. 1998. "Shovelnose Sturgeon" (On-line). Accessed October 23, 2004 at http://www.sbs.utexas.edu/bio354l/Projects/1998/Rodney_Bradshaw/Scaphirhynchus_platorynchus.html .

Evansville education, 2004. "Evensville education" (On-line). Fishes discovered by Rafinsque. Accessed October 25, 2004 at http://faculty.evansville.edu/ck6/bstud/raffish.html .

Everett, S., D. Scarnecchia. 2003. Comparison of Age and Growth of Shovelnose Sturgeon in the Missouri and Yellowstone River. North American Journal of Fisheries Management , 23/1: 230.

Keenlyne, K. 1996. Environmental Biology of Fishes. Life history and status of shovelnose sturgeon, Scarphirhynchus platorynchus , 48: 291-298.

Kynard, B., E. Henyay, M. Horgan. 2002. Ontogenetic Behavior, Migration, and Social Behavior of Pallid Sturgeon, Scaphirhynchus albus, and Shovelnose Sturgeon, S. platorynchus, with Notes on the Adaptive Significance of Body Color. Environmental Biology of Fishes , 63/4: 389-403.

Ohio Department of Natural Resourcs, 2004. "Fishing-Shovelnose Sturgeon" (On-line). Accessed October 22, 2004 at http://www.dnr.state.oh.us/wildlife/Fishing/shovelnose/shovelnose.htm .

U.S. Fish and Wildlife Service, 2004. "United States Fish and Wildlife Service" (On-line). Shovelnose Sturgeon. Accessed October 20, 2004 at http://midwest.fws.gov/Fisheries/topic-shovelnosesturgeon.htm .

US Fish and Wildlife Service, 2004. "Brochure-Shovelnose Sturgeon" (On-line). Accessed October 19, 2004 at http://midwest.fws.gov/Fisheries/library/broch-shovelnose.pdf .

US Fish and Wildlife Service, 2002. Shovelnose Sturgeon Iridovirus sampling in the Missouri River below Gavins point dam, South Dakota and Nebraska. US Fish and Wildlife Service Annual Report , 30: 265.

2004. "Mississippi Interstate Cooperative Resource Association" (On-line). Interjurisdictional Rivers of the Mississippi River Basin. Accessed October 18, 2004 at http://wwwaux.cerc.cr.usgs.gov/MICRA/SHOVELNO.HTM .