See more photos…
Fish Die-Off in Cottonwood Lake, Hellyer County Park, 9/5/22 by Ronald Horii
I heard about a fish die-off in Hellyer County Park's Cottonwood Lake from Bruce and Alie Victorine. They said they saw a huge flock of turkey vultures feeding on dead fish last Wednesday, 8/31/22. There was a BioBlitz at Hellyer, just a few days before on 8/28/22: https://tinyurl.com/2kvwrwh4. If there were any dead fish, people would have noticed them. I went to check it out on Labor Day, 9/5/22. I saw that the lake was very low. It's not a deep lake, so it doesn't have much farther to go before it dries up and kills all the fish in it. (It did that in 2015.) I saw a warning sign about toxic algae, which was there last week. On the south shore, I could see green scum on the surface of the water. This is probably blue-green algae, also called cyanobacteria. It's a naturally-occurring organism, but under certain conditions, it can bloom and produce toxins. These toxins can kill fish, injure other wildlife, make humans sick, and can even fatally poison dogs who drink the water. Here's information about cyanobacteria poisoning: https://www.cdc.gov/habs/materials/factsheet-cyanobacterial-habs.html. What I saw along the shore were carcasses of medium-sized carp. They are a non-native invasive species that were probably washed into the lake when Coyote Creek flooded the whole park in 2017. They are considered a "trash fish" and are not sought after by sports fishermen, so they tend to grow big. They feed along the bottom and tend to stir up sediment, which smothers the nests of more desirable fish. They are tough fish that can tolerate wide variety of environmental conditions, including warm, stagnant waters with low oxygen. So the fact that they're dying means the conditions must be really bad. Here's more information about carp: https://calfish.ucdavis.edu/species/?uid=25&ds=241. Here's more information about Hellyer County Park: https://parks.sccgov.org/santa-clara-county-parks/hellyer-county-park. Here are more of my pictures of Hellyer: http://www.rhorii.com/#Hellyer
I heard about a fish die-off in Hellyer County Park's Cottonwood Lake from Bruce and Alie Victorine. They said they saw a huge flock of turkey vultures feeding on dead fish last Wednesday, 8/31/22. There was a BioBlitz at Hellyer, just a few days before on 8/28/22: https://tinyurl.com/2kvwrwh4. If there were any dead fish, people would have noticed them. I went to check it out on Labor Day, 9/5/22. I saw that the lake was very low. It's not a deep lake, so it doesn't have much farther to go before it dries up and kills all the fish in it. (It did that in 2015.) I saw a warning sign about toxic algae, which was there last week. On the south shore, I could see green scum on the surface of the water. This is probably blue-green algae, also called cyanobacteria. It's a naturally-occurring organism, but under certain conditions, it can bloom and produce toxins. These toxins can kill fish, injure other wildlife, make humans sick, and can even fatally poison dogs who drink the water. Here's information about cyanobacteria poisoning: https://www.cdc.gov/habs/materials/factsheet-cyanobacterial-habs.html. What I saw along the shore were carcasses of medium-sized carp. They are a non-native invasive species that were probably washed into the lake when Coyote Creek flooded the whole park in 2017. They are considered a "trash fish" and are not sought after by sports fishermen, so they tend to grow big. They feed along the bottom and tend to stir up sediment, which smothers the nests of more desirable fish. They are tough fish that can tolerate wide variety of environmental conditions, including warm, stagnant waters with low oxygen. So the fact that they're dying means the conditions must be really bad. Here's more information about carp: https://calfish.ucdavis.edu/species/?uid=25&ds=241. Here's more information about Hellyer County Park: https://parks.sccgov.org/santa-clara-county-parks/hellyer-county-park. Here are more of my pictures of Hellyer: http://www.rhorii.com/#Hellyer
