Monitoring Reveals Signs of a Sturgeon Comeback in the Connecticut River

CT DEEP biologists use tagging and acoustic telemetry monitoring in Connecticut waters and Long Island Sound. LISS funding will help support the research in 2022. 

By Cheyenne Ellis

An underwater photograph of a shortnose sturgeon, taken in the Connecticut River.
An underwater photograph of a shortnose sturgeon, taken in the Connecticut River. Credit: Bob Michelson (Photography by Michelson), courtesy of CT DEEP.

With bodies encased in armored scales, sturgeon have been circling the ocean since the Triassic period (248-200 million years ago). These hardy fish have survived mass extinctions, falling meteorites, and even an ice age, only to meet their demise over 200 million years later at the hands of one single species—humans. 

Currently, of the 27 known species of sturgeon, up to 85 percent of them are classified at least as threatened; 63 percent are classified as critically endangered, according to the International Union for Conservation of Nature (IUCN). The Long Island Sound has two native species of sturgeon—the Atlantic and the shortnose—which are listed as endangered both federally and locally. One of the fish, the Atlantic sturgeon, migrates from the Atlantic Ocean to Long Island Sound and to local rivers when they are ready to breed, while the other, the shortnose sturgeon, live their lives almost entirely within several of Connecticut’s largest rivers.  

A team of researchers from the Connecticut Department of Energy and Environmental Protection (CT DEEP) first began tracking the movement of shortnose sturgeon using a catch and release tactic in the late 1980s, with visual tags attached to the sturgeon’s dorsal fins. They first began using acoustic telemetry in 2003. When beginning the research, scientists believed that Atlantic sturgeon no longer spawned in Connecticut rivers, but soon into their shortnose sturgeon findings, Tom Savoy, a fisheries biologist with CT DEEP, made an interesting discovery. 

“Very early on we began to notice that we were collecting the occasional Atlantic sturgeon,” said  Savoy. “That made us wonder if maybe the [Atlantic sturgeon] aren’t all gone…Maybe there’s still a few hanging around.” That proved to be the case. Many adult Atlantic sturgeon were located throughout the years, but for a while, young could not be found. Finally, in 2014, the first recorded young Atlantic sturgeon was born in the Connecticut River, reappearing after having been virtually extinct from the area for decades. 

A young Atlantic sturgeon, the size of one hand, is discovered in May 2014. It was the first-recorded hatchling in CT DEEP's sturgeon monitoring program on the Connecticut River.
This young Atlantic sturgeon, discovered in May 2014, was the first-recorded hatchling in CT DEEP’s sturgeon monitoring program on the Connecticut River. Multiple other young sturgeon were discovered in the following months. Credit: Tom Savoy (CT DEEP).

That proved to be the case. Savoy sought out a permit to work with both species and has since been doing yearly monitoring to better learn the habits and patterns of Connecticut’s sturgeon.  

Operations typically move slowly: state regulations indicate how many sturgeon can be studied each year, which usually falls between 10-20 fish. Each individual can only undergo one procedure (such as a tracker placement or an age check) to help prevent unintended harm to the fish. For that reason, each year of data is so critical for the long-term goals of the study. With Atlantic sturgeon only returning to breed once every 3-5 years, a single lost year could potentially throw off the understanding of the migrational patterns of certain sturgeon for up to a decade. Additionally, losing one year of data would mean the loss of 20 or so additional test subjects and the opportunity to perform additional research on the captured sturgeon. Numerous test subjects and a consistent stream of data are essential in order to find an accurate population count. 

With the project’s current funding expiring earlier this year, the Long Island Sound Study stepped in to cover the next year of expenses, which totaled around $100,950. The interim funding will allow the CT DEEP team to continue buying and installing acoustic monitoring trackers over the next year, while they reapply for long-term grants. Though Atlantic sturgeon have already completed their migration for the year, the funding will also help support the year-round monitoring of shortnose sturgeon in the river.

Present and Historical Populations of Atlantic Sturgeon 

(click dates to advance timeline)

Drawing of a shortnose sturgeon. Credit: Pixnio.

Drawing of a shortnose sturgeon.

245-280 million years ago

Sturgeon evolved from other Acipenseriform fish.

Colonial Jamestown in 1614. Credit: Wikipedia.

Colonial Jamestown in 1614.


Colonists arrive in Jamestown and begin using sturgeon as a food source.

A model of what a colonial-era ship would have looked like. Credit: Colonial Society of Massachusetts.

A model of what a colonial-era ship would have looked like.


Food markets were established and sturgeon meat was no longer required. Sturgeon were killed to make room for large ships.

The price of sturgeon caviar has increased as they became more endangered. Credit: Wikipedia.

A spoonful of sturgeon caviar is held above a small bowl containing sturgeon caviar.


Sturgeon caviar was discovered to be extremely profitable and the industry exploded. Sturgeon populations began to drastically decrease.

When shortnose sturgeon were listed, regulations on fishing and harvesting caviar were lifted. Credit: Flickr.

A sign that says "No fishing beyond this point" is nailed to a signpost.


Shortnose sturgeon were listed as federally endangered on March 11, 1967 (pre-dating the Endangered Species Act).

Connecticut River Estuary at Lord Cove. Credit: Cheyenne Ellis.

Connecticut River Estuary at Lord Cove.


Sturgeon populations reached an all-time low. Atlantic sturgeon were considered virtually extinct from the Connecticut River.

Atlantic sturgeon at the Aquarium du Québec. Credit: Wikipedia.

Atlantic sturgeon at the Aquarium du Québec.


Atlantic and shortnose sturgeon begin to show gradual signs of recovery, as more fish continue to be sighted.

The first-ever Connecticut River born Atlantic sturgeon hatchling. The discovery was made by CT DEEP biologists in May of 2014. Credit: Tom Savoy (CT DEEP).

The first-ever Connecticut River born Atlantic sturgeon hatchling, held by hand.


The first Connecticut River-born juvenile Atlantic sturgeon is found in the river by CT DEEP biologists.

Though exact population numbers are not clear, colonial-era writings tell of sturgeon so plentiful you could “walk across their backs,” or find your boat blocked by masses of sturgeon—Savoy reckons the number was probably in the millions throughout the East Coast. But what was once an abundant fish population in Connecticut rivers had dwindled so low by the 20th century that, until recently, they were considered virtually extinct from the area. Some studies estimate that there are currently fewer than 1,600 shortnose sturgeon in the Connecticut River, with even less Atlantic sturgeon visiting the river. Unfortunately, the reason for their decline is largely due to overfishing. Though few anglers have seen sturgeon in local waters, those who do catch a glimpse of their bony, prehistoric appearance can immediately put a name to the fish. Their unique appearance and large size has made them the ultimate catch for centuries. Atlantic sturgeon have been known to grow up to 16 feet in length and can weigh anywhere from 400-800 pounds.

Two Atlantic sturgeon underwater.
A picture of two Atlantic sturgeon underwater. These fish mature slowly, but by adulthood can reach up to 16 feet in length. Photo courtesy of NOAA Fisheries.

Early colonists and indigenous communities in the Northeast were well acquainted with Atlantic sturgeon—in fact, they depended on them. The return of sturgeon upriver each spring provided heaps of protein after long, cold winters with scarce food availability. As the colonies became more established and developed fishing industries, these same fish that had once sustained them began to be seen as a nuisance, breaking fishing equipment and preventing the capture of the smaller target species. Captured sturgeon were often slaughtered en masse, seen as being nothing more than a hindrance to boats trying to navigate the rivers. This would continue until the mid-1800s, when a profitable discovery proved even more tragic for sturgeon. 

Sturgeon caviar, which came to be known as “black gold,” became one of the most highly-sought delicacies in Europe. With the initial abundance of sturgeon in the rivers and the high costs Europeans were willing to pay for roe, the caviar industry took off exponentially—the US Fish and Wildlife Service estimates that at its peak, the East Coast harvested 7 million pounds of sturgeon in one year alone. But this business venture would prove to be short-lived. Over the next few decades, sturgeon harvest amounts were already on the decline (regardless of the unrelenting demand for caviar). Just one hundred years later, sturgeon harvest had decreased from 7 million pounds (which only accounts for the East Coast’s harvest) to a mere 400 pounds for the entire United States. 

As their decline became more apparent over time, many species of sturgeon were gradually added to endangered species lists across the country. Shortnose sturgeon were listed as endangered in 1967, predating the Endangered Species Act of 1973. Fishing regulations have greatly helped sturgeon populations, but recovery has still proved difficult. Spawning efforts are often disrupted by the presence of dams along the river, as well as other anthropogenic factors such as habitat loss, climate change, and water pollution. Sturgeon breeding habits do not make the process any easier. Sturgeon can live up to 100 years old and some species do not reach sexual maturity until they are around 20 years old. Certain types of sturgeon, like the Atlantic, only return to their natal river to spawn every 3-5 years and, of the million or so eggs they lay at a time, very few individuals survive to adulthood. 

Besides the extensive historical and cultural significance of sturgeon, these ancient fish are also very important to the ecosystem. For starters, they make incredible indicators of river health and water quality. Individuals may have lived through up to a century of environmental change, making their bodies rich sources of information. Sturgeon feed off of bottom-dwelling organisms like snails, mollusks, and small fish. In turn, their waste and eggs provide sources of nutrients for other aquatic organisms. The complete feeding and ecological habits of these fish are not fully understood because state regulations combined with the sturgeon’s own elusiveness make it difficult for these creatures to be studied. 

Listening for Sturgeon: How Acoustic Telemetry Transformed Research 

A ruler measuring a modern acoustic receiver, which is about 1 inch in length.
The approximate size of a modern acoustic receiver is only about 1 inch in length. Credit: Tom Savoy.

CT DEEP Fisheries Division biologists, including Savoy, Deb Pacileo, and Jacque Benway, are determined to learn as much about sturgeon as they can. To do this, they use an efficient catch and release monitoring system called acoustic telemetry. An acoustic transmitter is attached to an individual specimen during the capture part of the process and is released back into the water. Then, an acoustic receiver is placed in the water which can pick up the unique sound made by an individual transmitter and identify the specimen, as well their approximate location.  

Acoustic telemetry technology first originated in the mid-1950s. Prior to this, scientists could only use bands or markers that would allow them to easily identify specimen that they have seen before. CT DEEP began their research using acoustic telemetry, but the process was still rather labor intensive. Instead of having an anchored-down receiver in the water as they do now, a researcher had to hold a smaller receiver in the water from a boat and audibly listen for transmitters. The new receivers, which are still in the process of being purchased and installed throughout the Sound, are able to pick up unique sounds all day long that are up to half a mile away, allowing for more accurate data.  

The data collected from acoustic telemetry allows the team to make estimates about the population size. Using the number of tagged sturgeon versus the number of untagged ones they come across, scientists can wager a guess at population size and pick up on any notable changes from prior years.  

Sturgeon monitoring is very much a team effort: Atlantic sturgeon that Savoy placed a tracker on have been picked up by receivers as far away as the coastal waters of South Carolina. This information allows him to not only monitor the time and location of their spawning cycles, but also track their migrational patterns while they are at sea. 

“The Atlantic sturgeon can be out in the ocean for 10-20 years before they come back to the river,” said Savoy. “By having people up and down the East coast, we can all help each other out.” 

The team is not only interested in tracking the sturgeon. Of the few dozen sturgeon they are allowed to catch each year, several are studied for other characteristics rather than receiving a tracker. Recently, sturgeon have been examined to determine their age, sex, and feeding habits.  

Just as others are willing to aid in the sturgeon monitoring efforts, CT DEEP is more than willing to use their acoustic telemetry receivers to collect data for other organizations using the same tracking system. Any at-risk species who have been tagged for other studies such as sea turtles, sharks, American shad, black sea bass, striped bass, and even marine mammals, are monitored by these receivers. This information is uploaded to the shared online database called MATOS (Mid-Atlantic Acoustic Telemetry Observation System), which can then be examined by researchers across the country and shared with global tracking systems. 

Sturgeon in the Future 

We know so much about the role of sturgeon throughout human history, but what about their role in our future? 

There is reason to be hopeful—many species of sturgeon, including the Atlantic, have began making appearances in places they were long thought to have disappeared from. This is likely due to fishing restrictions, dam removals, and an increased water quality. If regulations continue to be enforced and restoration efforts continue, those at CT DEEP believe that it may be possible for sturgeon populations to recover. 

CT DEEP scientists plan to keep tracking sturgeon for as long as they are able to. Savoy hopes to continue his research on sturgeons by examining other variables including the effect of contaminant loads on sturgeon. 

“We know that there’s a lot of human endocrines in the water, so we need to find out if these are impacting [sturgeon],” said Savoy. Studies on other fish have shown impacts on egg fertility and sex organs. 

Additionally, CT DEEP is planning to launch an app which will allow the public to easily report any dead sturgeon that they may happen across on the water. Because of limits on the number of sturgeon that can be studied each year, collecting these remains give them the opportunity to perform more studies, as well as keep track of locations where the sturgeon were found.  

Sturgeon have truly survived more natural disasters than almost any other species on this planet. Even when they are seemingly on the brink of extinction, they manage to pop back into the water; survival is in their very DNA. It is this innate resilience that is our greatest hope when it comes to helping this ancient species recover and swim back into our waterways. 

In the 40 years that Tom Savoy has been researching sturgeon, he has encountered one of the same fish over 10 different times. Another was recently seen again after being tagged 29 years earlier! To learn more about sturgeon and his study, please check out the “Sturgeon: Connecticut’s Living Dinosaur” story map, made by CT DEEP.

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