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Threats to Atlantic and Shortnose Sturgeons

Although it is no longer legal to fish for or keep Atlantic and shortnose sturgeons due to their Endangered Species Act listings, they are still caught accidentally as bycatch in some commercial and recreational fisheries. Both species are particularly vulnerable to fisheries that fish with gill nets. The fishery practices commonly used with gill netting involve setting and leaving nets for long periods of time, anywhere from several hours to days. Atlantic and shortnose sturgeons swim into these nets and can get stuck. If their gills get closed shut by the nets, they can suffocate and die. Another threat posed by nets is what happens when nets are lost. Due to weather, storms, and rough waters, nets can break free and get lost. These are called “ghost nets” and can float around the ocean and rivers entangling sturgeon as well as marine mammals and sea turtles.

Dams on rivers pose another threat to Atlantic and shortnose sturgeons. Dams were constructed on many rivers along the East Coast. They were made for many reasons including production of electricity through hydropower and for diversion of water for agriculture. Dams can be harmful to  sturgeons by blocking the way to their spawning grounds. If they are unable to reach their spawning grounds, they may choose to not spawn at all, or end up spawning in an area that is not suitable for the development of embryos. Many dams have special fish ladders or fish ways that are designed to allow for the passage of fish upstream of the dam. Sturgeon, however, do not use the fish ways to pass the dam, and even if they did, there have not yet been suitable methods designed for passage back downstream.

tidal turbines

Sturgeon can also be harmed by tidal turbines, another form of hydropower. Some tidal turbines look like fans under the water. The power of the tide makes the fan spin, and this motion creates energy. If sturgeon swim near these turbines, they can be struck by the blades of the fan. Similar to the dangers that tidal turbines pose, vessel strikes pose a threat to sturgeon as they can be struck by the blades of a propeller as a boat is passing.

Pollution and dredging can also be detrimental to sturgeon survival. Pollution can be caused by many different actions, and can include run-off from agricultural sites, roadways, construction sites, and pesticide applications. All of these things can affect water quality. A couple of water quality factors that affect sturgeon are dissolved oxygen and temperature. Run-off from agricultural sites can include fertilizer which can cause harmful algal blooms. When algae blooms, it can take oxygen out of the water which can kill fish and other aquatic life. Temperature is another factor that can affect the migration spawning cues for sturgeon. The spawning migration begins with the rise in temperature in the spring. Hatching time and egg development are also dependent on temperature.

Dredging is another potential threat to sturgeon, and is when the river bottom is dug up to either make the river deeper or wider. Sturgeon can be caught in the dredge and killed. Dredging can affect spawning habitat as well by suspending fine particles and pollution which can cover over the gravel and cobble substrate that is needed for spawning.

Summary of Threats