APOPKA, Fla. – State agencies investigating a massive fish kill in Lake Apopka say they’ve ruled out some possibilities but are still unsure what caused the incident.
News 6 first reported on what was happening primarily on the southern and western shoreline last week, after people reported seeing dead fish line miles of the lake’s edge in early February.
Both the Florida Fish and Wildlife Conservation Commission and St. Johns River Water Management District have collected water samples from the area. At a board meeting this week SJRWMD Executive Director Michael Register told the governing board that those lab samples did not show “any measurable detects of toxins.”
A spokesperson for FWC told News 6 in an email that the water samples tested so far have not identified a clear cause, including algal blooms or low dissolved oxygen.
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Register said at Tuesday’s board meeting that it’s also unlikely that some type of runoff of toxin came into the lake from recent rainfall. He said disease was also discussed, but that was ruled out because of the wide variety of species involved.
“Temperatures did drop fairly low but not really low enough to kill the native species that were found,” said Register. “There is some speculation that rapid change in temperature from cold to warm that happened during that time period that some of the bass and others can be sensitive to that, especially during spawning season which is going on right now.”
Register added that FWC is doing some necropsies on the fish and gathering more data as the investigation continues.
St. Johns Riverkeeper, a nonprofit organization that advocates the river’s protection, shared pictures with News 6 of more recent fish kills in the Jacksonville area.
“We’ve been getting fish kills from all over,” said Soraya Aidinejad, an advocacy specialist. “We’ve gotten some in the Intracoastal. We’ve gotten some in Ribault, in Moncrief Creek. The first time I witnessed it was when we were on a boat trip a couple weeks ago, and I saw all these dead fish, and I’m like, ‘oh my gosh.’”
Aidinejad said unlike the large-scale fish kill in Lake Apopka where a wide variety of fish have been impacted, what they’ve seen in the St. Johns River is tilapia, a non-native species, that have died.
“When we had that cold snap a couple weeks ago, that dramatic drop in water temperature caused that die-off,” said Aidinejad. “They prefer warm water that is typically between 60 to 80 degrees and when we had that cold snap, their tolerance wasn’t up to par with that cold water temperature.”
Tilapia are considered an invasive species and can have a significant impact on the native ecosystem of the St. Johns, according to St. Johns Riverkeeper, because they take away food sources and space from native species and can even disturb the river’s essential grasses.
“It can lead to a complete collapse of aquatic communities, and without natural predators introduced in their environments, their populations grow unchecked,” said Aidinejad.
FWC says fish kills can occur in Florida waterbodies for all sorts of reasons: low dissolved oxygen, harmful algal blooms like blue green algae, fish-borne diseases, and severe weather events, name just a few. You can find more information about this on FWC’s webpage.
Fish-kill reports from the public are vital in responding to events like this, and officials encourage the public to please submit fish-kill reports to FWC’s Fish Kill Hotline at 800-636-0511.
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