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Dead fish seen in the Bronx River

201610039(1)

What’s going on?

Many people have been reporting seeing a number of dead fish floating in the Bronx River, especially around Starlight and Concrete Plant Parks. While seeing dead fish floating on the river or decomposing on the shore is not a pretty sight, it is not always cause for alarm. Bunker fish, also known as Menhaden (Brevoortia tyrannus), have recently been seen washing ashore around the region. These fish often are chased by predators, such as Bluefish (Pomatomus saltatrix) and Striped bass (Morone saxatilis), into large schools. When too many fishes are confined in a small, shallow area, they can deplete the Oxygen supply and die from suffocation. 

 
Another reason for the low Oxygen supply is input of nutrients causing aquatic plants to grow rapidly and widely in the river. These plants can be tall and stick up out of the water, can float on top (like algae or duckweed), or they can be entirely submerged underwater (like Pondweed). During the summer when the sun is shining, these plants are responsible for adding lots of Oxygen into the water for the fish and other critters to breathe, but too many nutrients can cause algal blooms and result in dangerously low Oxygen levels. This is because as the plants die and decompose, they use up the Oxygen and give off Carbon Dioxide (CO2), making it hard for species to breathe.

Nutrients (like Nitrogen and Phosphorus) enter the river through a number of different paths, whether directly from storwater outfall pipes or via runoff from fertilized lawns and golf courses. Combined sewer overflows (CSOs) also may be contributing excess nutrients into the river, releasing untreated sewage during heavy rains when the wastewater treatment plants become overwhelmed. Although algal blooms can occur naturally, they are made worse by excess nutrient loading.

 

The Alliance has developed a number of different projects that directly target preventing these pollutants from entering the river in the first place. Together with partner organizations, we are monitoring conditions and following the situation closely to see if there is a link to the annual fish die-offs seen around the region.
 

Photo credit: Damian Griffin

What can you do to help?

While there is not much we can do in the short run, we can all play a part by conserving water, especially during rain storms; reducing or elimnating fertilizer applications to lawns; preventing direct dumping into storm drains; supporting a strong Long Term Control Plan for controlling CSOs into the Bronx River; and/or getting involved in one of our water quality monitoring programs as a Citizen Science Steward. You can help us identify problems on the river by continuing to report these observations to us directly.

For more information about water quality of the river, please visit: www.bronxriverwater.org.

 
 
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About the Bronx River Alliance

The Bronx River Alliance is a coordinated voice for the river that works in partnership to protect, improve and restore the Bronx River corridor so that it can be a healthy ecological, recreational, resource for the communities through which it flows.

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