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Last updated on Friday, July 28, 2017
(GREENE CO.) - Thousands of fish are floating belly-up in Greene-Sullivan State Forest Reservoir 26.
Steve Siscoe, property manager says oxygen depletion is one of the most common natural causes of fish kills. The hypoxic event may be brought on by factors such as algae blooms, droughts, high temperatures and thermal pollution.
"The hot weather from last week caused a large algae bloom in the reservoir, and cloudy conditions Saturday and Sunday morning caused the algae bloom to die," Siscoe says. "When the algae bloom decomposes, it steals the oxygen from the water. Without the oxygen the fish die."
Shallow, weedy ponds are more susceptible to kills. The 42-acre reservoir located on Greene-Sullivan State Forest had an average depth of 4.5 feet with a maximum depth of approximately 12 feet.
Warm water holds less dissolved oxygen than cold water, so summer is the time when fish can have a hard time getting enough oxygen. Other organisms use oxygen, too, including the algae that grow in the summer and bacteria that degrade organic matter. During the day, the algae produce oxygen through photosynthesis, but at night, when photosynthesis stops, they and other organisms keep respiring, using up oxygen.
So on warm summer nights during algal blooms, the dissolved-oxygen concentration sometimes drops too low for the fish, and a die-off can occur which is what happened at the reservoir.
Most of the fish killed were gizzard shad, but there were some catfish, bass, crappie and bluegill found. Siscoe says the remaining fish will repopulate.
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