Aquatic Species at Risk - Green Sturgeon

At a glance

Green sturgeon have a prehistoric look. Not surprising, since they have pretty much remained unchanged for many millions of years. They are one of the world’s most ancient species. Like a smaller sibling to the enormous white sturgeon, the green sturgeon is one of the largest and longest-living species of fish: reaching up to 70 years in age, up to 2.3 metres in length, and weighing as much as 159 kilograms. Damming and diking of rivers, water temperature changes, pollution, and fishing have harmful effects on green sturgeon.

About the green sturgeon

Green sturgeon spend most of their lives in salt water but return to freshwater rivers to spawn. They are bottom dwellers and feed on marine creatures such as shrimp, crabs, shellfish, and other fish that live on the ocean floor. Green sturgeon are slow-growing and late maturing. Their first one to four years are spent feeding and growing in freshwater before moving out into the ocean. Males reach maturity at about 15 years of age, while females at about age 17. Every three to five years, adult green sturgeon return to the spawning sites where they were born—areas of large rivers with swift currents. They have few known predators other than some marine mammals and, of course, humans.

How to recognize the green sturgeon

Green sturgeons are easy to spot—if you’re lucky enough to ever see one. These dinosaurs of the deep have four barbels—food-sensing whiskers—in front of their mouths, which are located on the underside of their long snouts. And instead of scales, they have denticles—tiny toothlike projections that protect their bodies. But most notable about their appearance are the rows of sharp bony plates that armour their sides and backs, making them look prehistoric. Also, green sturgeon have dark olive-green bodies, with a single dorsal fin located in front of a sharklike tail.

Where the green sturgeon lives

The green sturgeon lives in the Pacific Ocean, from Mexico to Alaska. In Canada, it is occasionally found on the West Coast in marine waters or in the lower reaches of large rivers. Green sturgeon sightings have been reported from the lower Fraser, Nass, Stikine, Skeena and Taku rivers of British Columbia. Green sturgeon tend to lumber along river bottoms and ocean floors. Younger green sturgeon call the lower reaches of coastal rivers home until they reach four years of age, when they are large enough to move out to the ocean. They return to rivers as adults to spawn. Unfortunately, very little is known about abundance and distribution in Canada. Green sturgeon spawning and rearing has not been documented in Canada, only in the US. The species may occur in Canadian waters only for feeding.

Why the green sturgeon is at risk

Green sturgeon meat is said to be oily, with an unpleasant taste, so the fish has been of limited value and use to people compared to other highly desired sturgeon species. Its abundance in Canada has likely always been low. Green sturgeon are still caught occasionally as bycatch in West Coast fisheries, but its other threats are probably limited to the US portion of its range, including dams, dikes, and industrial activities in freshwater habitats. These impacts can affect the availability and suitability of habitats for spawning and rearing. Also, because of their long lifespan, green sturgeon are vulnerable to ongoing buildup of contaminants in their bodies.

What’s being done

The green sturgeon is listed under the federal Species at Risk Act (SARA) as a species of Special Concern. The species is also protected by the federal Fisheries Act which prohibits destruction of fish habitat. It is also illegal to keep any green sturgeon caught while sport fishing in Canada. The green sturgeon species worldwide is also protected by international law under the Convention on International Trade of Endangered Species (CITES).

A management plan for the green sturgeon is currently being developed.

What can you do?

Green sturgeons will get the protection they need only if all Canadians work together to reduce threats. Find out more about the green sturgeon and be aware of human-induced threats. Do your best to reduce threats wherever possible to better protect the green sturgeon and its habitat. Get involved with the Habitat Stewardship Program for Species at Risk(HSP) or another conservation organization. 

Background information provided by Environment Canada, March 2006.