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Fremont blames heat for massive Lake Elizabeth fish die-off


City of Fremont workers push shopping carts loaded with dead fish they cleaned out of Lake Elizabeth at Central Park in Fremont, Calif., on Friday, July 5, 2024. Several fish species die due to low oxygen levels during the Bay Area's recent heatwave. City spokeswoman Geneva Bosques said that an estimated 1,000 fish, including catfish, trout, carp, Sacramento Suckerfish, and crappie, have been found dead in the lake since Wednesday. Ray Chavez/Bay Area News Group)

About 1,000 fish at Lake Elizabeth in Fremont’s Central Park have died this week after the excessive heat wave caused low oxygen levels in the water, according to a city spokesperson.

With city high temperatures in the mid-to-upper 90s the first half of the week, the lake got hotter and oxygen levels dropped, suffocating close to 1,000 fish since Wednesday.

“Fish dying off in Lake Elizabeth in the summer is not completely unusual. We do get a small number of fish that die off every year,” city spokesperson Geneva Bosques said. But this year’s heat wave is doing unexpected numbers on the lake’s fish population.

The city sent a specialist with Livermore-headquartered Applied Marine Sciences to take test samples of the water to inspect oxygen levels and the possibility of an algae bloom, Bosques said. But she added there is no “visible indication” of a dangerous algae bloom, such as the one that killed off thousands of fish in Oakland’s Lake Merritt during a 2022 heat wave.

“It’s so hot and the water is so shallow, in the last couple of nights, the air hasn’t cooled off enough to lower the temperature at night,” Bosques said. “We haven’t gone in to do an in-depth analysis but we believe it’s gotten shallower over time.”

The deepest parts of the lake, once around 5 feet, are now about 4 feet, Bosques said, and 2-3 feet deep where the lake is shallowest.

Bosques added that the city’s specialist is evaluating the cause of the die-off, but the lack of oxygen is likely the main contributor to the deaths.

“The consultant estimates that the issue is due to a diminished Dissolved Oxygen (DO) level that is stressing the fish and causing the die-off,” the city said in a statement released Friday afternoon. “A DO level of 5.0 mg/L concentration is the standard target and ours is currently just below 1.0.”

The city owns a small part of the lake but it is mostly owned by the Alameda County Flood Control District, which regulates the water going in and out of the lake. The city has an agreement with the flood control district to maintain the lake, according to Bosques, and used an automated pump to increase the flow of fresh water this week due to the heat.

The city stocks the fish annually with a few hundred pounds of both catfish and trout, Bosques said, but the species of fish found floating in the lake also include Sacramento sucker, crappie and carp, which are not supposed to be in the lake.

City of Fremont workers push shopping carts loaded with dead fish they cleaned out of Lake Elizabeth at Central Park in Fremont, Calif., on Friday, July 5, 2024. Several fish species die due to low oxygen levels during the Bay Area’s recent heatwave. City spokeswoman Geneva Bosques said that an estimated 1,000 fish, including catfish, trout, carp, Sacramento Suckerfish, and crappie, have been found dead in the lake since Wednesday. Ray Chavez/Bay Area News Group) 

Mark Carr, a professor of marine ecology at …read more

Source:: The Mercury News – Entertainment

      

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