Shortnose Sturgeon
Acipenser brevirostrum
Fish illustration used with permission. Source: Animalia.bio
Common name: Shortnose sturgeon
Scientific name: Acipenser brevirostrum
Range: Historically, shortnose sturgeon have been found in the majority of coastal rivers along the East Coast of North America, from Florida to maritime Canada. Today, they can be found in 41 bays and rivers, but their distribution is more scattered. Individuals along the East coast are split into three large “metapopulations”, of genetically similar individuals. There is a large gap of about 250 miles separating the northern (Acadian) and mid-Atlantic (Virginian) populations from the southern (Carolinian) population, meaning that it is unlikely that these adults will ever meet to breed.
In Maine, Shortnose sturgeon are concentrated in the south and mid coast, particularly in the Penobscot, Kennebec, Androscoggin, and Piscataqua rivers. They have also been observed foraging in the St. George, Medomak, Damariscotta, Sheepscot, and Saco rivers, and there have even been a few rare sightings in the downeast region. Unlike other species of sturgeon, they spend most of their time in the estuaries of these coastal rivers, and relatively little time in the ocean.
Identification: The shortnose sturgeon is one of Maine’s two sturgeon species, the other being the Atlantic sturgeon. While they look very similar to each other, shortnose sturgeon can be distinguished by their smaller size, larger mouth, smaller snout shape, and tail scute pattern.
Shortnose sturgeon have a protruding snout with four barbels (fleshy, whisker-like projections) that hang in front of a large, underslung mouth. Their name references the fact that their snout is shorter and more conical shaped than other species. They do not have teeth; their barbels help locate prey which is then sucked into their mouth like a vacuum.
Instead of scales, five rows of bony plates called scutes run along the length of their body. Their bodies are generally yellowish brown, darker on the head, back, and sides, and a milky-white to dark yellow color on the belly. Shortnose sturgeon can grow to 4.5 feet long and weigh up to 60 pounds, but are commonly smaller.
Life history: Shortnose sturgeon are a relatively long-lived species. Their average lifespan is around 30 years, but the oldest known female reached 67 years of age and the oldest known male was 32. Shortnose sturgeon are slow-growing and late-maturing, often not reaching reproductive maturity until they are 10–12 years old. Their lifespan is correlated with where they live, with northern populations living longer and maturing more slowly than southern populations.
The shortnose sturgeon is anadromous, spending some time in salt water but always returning to spawn in freshwater. However, shortnose sturgeon are more specifically amphidromous, meaning their preference is for fresh or brackish water. They are born in freshwater and live primarily in their natal river, make short feeding or migratory trips into salt water, then return to freshwater to feed and escape predation. Unlike most fish species, spawning is not a yearly event for most shortnose sturgeon. Males tend to spawn every other year and females every third year, although Maine’s shortnose sturgeon may spawn only once every five years. They spawn in flowing waters at water temperatures ranging from 46-65 ºF and require solid substrate for the eggs, which are adhesive. Females lay between 40,000-200,000 eggs depending on age and body size, which hatch in approximately 13 days. Newly-hatched fry are poor swimmers and drift with the currents along the bottom. As they grow and mature, the fish move downriver into the estuary.
Adult shortnose sturgeon stay in groups upstream in the winter, then move downstream. Sturgeon are social and will follow a leader, moving between different wintering sites. Their overwintering sites may be connected to where they choose to spawn come springtime, but this hasn’t been fully confirmed.
Diet and Behavior: Despite being quite large and primitive-looking, shortnose sturgeon are bottom feeders. They use their whisker-like barbels to locate prey in the muck, which typically includes invertebrates such as insects, crustaceans, worms, and mollusks, then use their extendable mouths to vacuum it up.
Both shortnose and Atlantic sturgeon have enjoyed a bit of fame from their habit of leaping completely out of the water on their way upriver to spawn. However, scientists are still trying to understand why. There are several theories, such as communication, or to dislodge itchy sea lice. The theory currently gaining the most traction is that they jump to fill their swim bladders with air, which helps control where they can go in the water column. Research has found that they will change their location in the water column after jumping, and jump more frequently during tidal changes, which supports the swim bladder theory. The best time to see sturgeon jumping is between May and August, especially when the tide is changing. In Maine, good viewing spots can be found along the lower Androscoggin and Kennebec Rivers, such as below the Brunswick dam or just downriver from the site of the former Edwards dam.
Cultural importance: Humans have a longstanding relationship with sturgeon. Both sturgeon species provided an important food and trade source to native peoples and early European settlers. The Wabanaki, who have stewarded the land and resources of northeastern New England for thousands of years, harvested sturgeon and had a spiritual connection to the fish. The name of the Passagassawakeag River is Native in origin and is believed to mean, “a place for spearing sturgeon by torchlight.”
Research: Research is widespread and ongoing, involving universities, nonprofits, and even the US Navy, who are working on a study of sturgeon activity in the lower Kennebec around Bath Iron Works. Adult sturgeon are tagged and tracked using equipment placed in rivers, at dams, or in labs where they are studied post mortem. Data suggests there’s something the sturgeon like about the Penobscot River, as a high percentage of tagged sturgeon that leave the river and travel to other Maine rivers eventually return.
Threats: The major causes of historic population decline for sturgeon were overfishing and the loss of habitat from dams. Like lobster, there was a time when sturgeon eggs (caviar) were a cheap food, consumed only by the “lower” classes. However, when this changed the markets exploded, and great demands for both caviar and the fish's smoked flesh resulted in swift overexploitation of sturgeon stocks. Additionally, the fish were increasingly cut off from accessing spawning habitat thanks to the numerous dams built across nearly every river in Maine. Dams not only fragment populations by limiting fish movement, but can also alter water flow and sediment patterns impacting spawning success. Today, hydroelectric dams are still a threat, causing mortality if fish swim too near intake pipes and pass through turbines.
Today, other threats include river habitat degradation, channel dredging, poor water quality, contaminants, fisheries bycatch, incidental boating strikes, and climate change. Sturgeon depend on clean, oxygen rich water, and can be an indicator of good water quality, or lack thereof. Due to their long life spans and late age of maturity, populations will likely be slow to recover. Additionally, there is still much we don’t know about sturgeon, so continued research is needed.
Restoration efforts: Officially listed by the National Marine Fisheries Service as endangered, the shortnose sturgeon is fully protected by the Endangered Species Act. This action, combined with ongoing water quality and habitat protection efforts, aims to help replenish populations.
In the last two decades, endangered shortnose sturgeon have regained access to historic habitat following a handful of major dam removals. The removal of the Edwards Dam on the Kennebec River in 1999 and the Veazie Dam on the Penobscot river in 2013, reconnected their historic range for the first time in a century. Researchers at the University of Maine confirmed the presence of shortnose sturgeon in the Penobscot river between Veazie and Orono by fall 2015, showing that the fish were indeed using the newly available habitat. In time, access to these and other spawning grounds may help the fish to recover.
Anyone can get involved in helping to restore sturgeon. If you find a dead, entangled, or stranded sturgeon, report it to NOAA by sending an email to noaa.sturg911@noaa.gov or by calling a local office. This allows scientists to collect samples and data to better understand sturgeon populations, track recovery efforts, identify threats, and fill in gaps in our knowledge. For more information, click here: https://www.fisheries.noaa.gov/new-england-mid-atlantic/endangered-species-conservation/report-stranded-injured-or-dead-sturgeon
Fishery: Indigenous peoples, including the Wabanaki, harvested sturgeon long before Europeans arrived in North America. Some sources credit the sturgeon as the primary food source that saved the Jamestown settlers in 1607, though the earliest documented fishery in Maine was in 1628 at Pejepscot Falls on the Androscoggin River. In the mid-1800s, Atlantic and shortnose sturgeon began to support a thriving and profitable fishery for caviar, smoked meat, and oil. For the most part, historical landings records failed to differentiate between shortnose sturgeon and the larger Atlantic sturgeon, making it difficult to determine historical trends in abundance for populations of either species. However, it is likely that the larger Atlantic sturgeon were the preferred targets.
By the late-1800s, sturgeon were being thoroughly over-exploited. Across their range, sturgeon catches peaked around 1890, though the peak may have been a few decades earlier in Maine. In 1890, over 7 million pounds of sturgeon were caught in a single year. Shortly after, landings declined rapidly, and by 1920, only 23,000 pounds of sturgeon were caught annually. Landings continued to decline through the 20th century, leading to the enactment of strict regulations. In 1983, Maine closed the tidal waters of the Kennebec and Androscoggin to the harvest of sturgeon, and instituted a 72-inch minimum size for other areas. In 1992, the harvest of sturgeon (both species) became illegal in Maine’s coastal waters. Today, both shortnose and Atlantic sturgeon are protected under the Endangered Species Act, and harvest is strictly prohibited.
Sources:
https://www.mass.gov/info-details/species-spotlight-shortnose-sturgeon
https://dec.ny.gov/nature/animals-fish-plants/shortnose-sturgeon
https://mainerivers.org/river-life/shortnose-sturgeon/
Squiers, Tom. Sturgeon Status in the Kennebec River. Friends of Merrymeeting Bay speaker series, 4/13/2016. (https://cybrary.fomb.org/pages/20160413_Squiers-FOMB-Royalty_of_the_River-Kennebec_Sturgeon_Status.pdf)