Shortnose Sturgeon
Acipenser brevirostrum
Distribution: Shortnose sturgeon are found in large coastal rivers and estuaries from New Brunswick south to Florida. Early records suggest that sturgeon were once able to move as far upstream on the Merrimack River as Amoskeag Falls. They were also once thought to be common in the Piscataqua River.
Description: Shortnose sturgeon have a prehistoric appearance, with a long pointy snout and 5 rows of hooked plates, called scutes, along its body instead of scales. They are a heavy bodied fish with an overall shape that resembles a shark in appearance. The large dorsal fin is positioned on the rear third of the body, just above the anal fin. The upper lobe of the caudal fin extends past the lower lobe. Shortnose sturgeon reach a length of about 4 feet, which is much smaller its relative, the Atlantic sturgeon, which can reach a length of 14 feet.
Species commonly confused with: Atlantic sturgeon
Habitat: Shortnose sturgeons occupy freshwater rivers, estuaries, and nearshore coastal habitat. They prefer to spawn in areas of a river with moderate flow and gravel or cobble substrate. Foraging areas are river sections that contain abundant benthic invertebrates, usually over sand or mud.
Life History: Adults return to specific spawning reaches in their natal rivers. They are a slow growing species, with age at maturity increasing as one moves north. In the St. John River, males may begin spawning within 1 to 2 years after reaching maturity (at 10 to 12 years), but females may not begin spawning until 5 years after reaching maturity (at 12 to 18 years). The average life span is about 30 years, but ages as high as 67 years have been documented.
Spawning substrates consist of boulder, cobble, and gravel with water depths of 10 m or less. Water temperatures during spawning range from 9.0 to 18.0°C. Spawning runs were observed during late April in the Merrimack River, Massachusetts. Adults forage on sandy and muddy substrates often near the upper reaches of tidal influence. They use fleshy barbels on their pointed snouts to detect benthic invertebrates with their sucker-like mouths, which they use to vacuum up their prey. Shortnose sturgeon remain in preferred river reaches for overwintering. In northern populations they do not feed during the winter months.
Recent tagging studies using acoustic telemetry have revealed that some shortnose sturgeon are more migratory than previously believed. Individuals tagged in the Kennebec and Penobscot Rivers have been found to move between the two river systems. Shortnose sturgeon tagged in the Merrimack River have been detected in the Kennebec River. Multiple tagged individuals have been detected by acoustic telemetry receivers deployed forunrelated projects in the Piscataqua River and Great Bay. It is possible that shortnose sturgeon routinely move between multiple foraging areas among the rivers and estuaries that flow into the Gulf of Maine.
Origin: Native
Conservation/Management: Shortnose sturgeon are federally listed as endangered. Until the recent detections of tagged fish by an array of acoustic telemetry receivers in the Piscataqua River and the Great Bay estuary, shortnose sturgeon had not been recorded in New Hampshire waters since 1971. Population declines due to the development of barriers (such as dams) in coastal rivers, alteration of spawning habitat, and commercial harvest have been well documented. Access to the upper portion of the Merrimack River is blocked by the Essex Dam in Lawrence. A fish elevator at the Essex Dam on the Merrimack River in Massachusetts has never recorded sturgeon use, although spawning activity has been documented a few miles downstream. The shortnose sturgeon population in the Connecticut River cannot move upstream of the Turner's Falls Dam in Massachusetts. Shortnose sturgeon in the Connecticut River was divided into two distinct populations by the Holyoke Dam until recent fish passage improvements at the dam made it possible for sturgeon to pass upstream using a fish lift and also pass safely downstream.
A recent status assessment of shortnose sturgeon in the Merrimack River suggests that the population may have expanded since surveys were last conducted in the late 1980's. Recent studies have also identified larger than expected populations in the Androscoggin, Kennebec, and Penobscot Rivers. Interestingly, only the Merrimack River and the Kennebec River appear to support spawning populations of shortnose sturgeon. Shortnose sturgeon native to the Kennebec River have been captured in the Merrimack River, but later detected in the Kennebec River during the spawning season. It appears that shortnose sturgeon may move extensively between coastal river systems to forage, but return to their natal rivers to reproduce. Bans on the commercial harvest of shortnose sturgeon and their eggs, for caviar, may be aiding in their recovery. Understanding the importance of movement between river systems and identifying critical foraging and spawning habitat will help further the recovery of this unique species.