Maine’s Amazing Sturgeon

On May 23, 2023, Dr. Gayle Zydlewski, Professor at UMO’s School of Marine Science, shared information about sturgeon, especially the two species that inhabit Maine rivers and coastal waters—the short-nosed sturgeon and Atlantic sturgeon. You can watch her entire presentation here or at the end of this summary.

Sturgeon have been around for approximately 200 million years—since before the dinosaurs. Short-nosed sturgeon—one of two species occurring in Maine—have bony plates along their backs called ‘scoots’ and bony plates on their head. They are sometimes referred to as ‘living fossils’ because sturgeon fossils from 65 million years ago are very similar to their form today.

Humans have a longstanding relationship with sturgeon. 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.’

Sturgeon occur in nine regions in the Northern hemisphere, but Dr. Zydlewski focused primarily on North American species. There are 27 species of sturgeon, most of which are very large animals. The Atlantic sturgeon can grow to 800 pounds, 12 feet long, and live for 50 years. Surprising, their diet is comprised entirely of invertebrates they collect from sandy bottoms.

Of the 27 species, the ranges of 19 are shrinking and many are at risk of extinction. All species of sturgeon are declining and it is one of the most endangered fish species groups today. Sturgeon are harvested commercially for caviar, often through poaching although they are legal to harvest in some places.

Sturgeon are vulnerable to population decline because they mature late (most don’t reproduce until five years old, some even later) and they don’t reproduce every year. Maine’s shortnose sturgeon may spawn only every five years.

The life history of Atlantic and shortnose sturgeon is similar to salmon. They spawn in freshwater. Adults migrate up rivers in May and June where they spawn in rocky bottoms. Juveniles stay in freshwater for 4-5 years, then go to the ocean, although large numbers of Atlantic sturgeon go to estuaries.

In recent decades, scientists have been catching and tagging sturgeon to track their movements. Some of the results have been surprising, contradicting prior beliefs about their movement. Shortnose sturgeon stay in groups upstream in the winter, then move downstream. Data suggests there’s something they like about the Penobscot River, as a high percentage of tagged sturgeon that leave the river eventually return. Many leave the Penobscot and travel to other Maine rivers, then return. Sturgeon are social and will follow a leader, moving between different wintering sites.

Data suggests that Atlantic sturgeon like to travel, moving from Maine rivers to NY, Canada, and places unknown.  Some show up all around the Gulf of Maine, others just offshore of the rivers.

Sturgeon are impressive because of their size and their habits. Scientists are still trying to understand their habit of leaping completely out of the water. There are several theories, such as communication, or to dislodge itchy sea lice. But the theory gaining the most traction at present is that they jump to gulp air to fill their swim bladder. Gulping air helps them control where they can go in the water column. Research has found that they jump more during tidal changes and change their location in the water column after jumping, lending credence to the swim bladder theory.

The biggest threats to sturgeon today are: entanglement in fishing gear; habitat loss; vessel strikes; and predation by seals. The biggest decline in sturgeon populations was believed to coincide with construction of dams in the early 1900s, limiting their access to spawning grounds. You can learn more about the role of dams in fish ecology in a prior presentation on the role of dams in the ecology of the Androscoggin River.

What can we do to help protect sturgeon? Data is always helpful, so take photos and send information about the size and condition of any sturgeon you see, dead or alive, to either of the following:

If you want to see sturgeon jumping, between May and August is prime time, especially when the tide is changing. Below the Brunswick dam is one good place. Another is at the dog park in Augusta, located at the site of the former Edwards dam (also downriver a bit near the railroad trestle).

There’s much more detail and information in the recording, which you can watch below. Learn more about Dr. Zydlewski’s sturgeon research at her website here: