Mullet with missing scales and lesions prompt investigation on St. Johns River

State officials are investigating reports of lesions and ulcers in mullet and other fish in springs along the St. Johns River and whether the lesions are related to blue-green algae blooms in the river.

Joe Cruz of Deltona was snorkeling at Blue Spring State Park last week when he was surprised to notice ailing mullet in the spring run.

"I was a little bit shocked because they look really, really bad," said Cruz. "They kind of looked like a zombie fish; I thought they looked almost dead."

He took a few photos and a video and then reported it to the Florida Fish and Wildlife Conservation Commission and posted photos on social media.

His report was one of a series of reports that began April 18, said Catalina Brown, coordinator of the wildlife commission's fish kill hotline.

"We have received 15 reports, either reports of fish kills or abnormal looking fish or information requests" for an area including Lake George, and two springs on its western shores, Salt Springs and Silver Glen Springs, Brown said. "Citizens were describing mullet with scales off, red skin and lesions."

Simultaneously, a blue-green algae bloom is underway in the St. Johns River, in Lake George and the two springs.  Another blue-green algae bloom is underway to the south, in the river’s headwaters near Fellsmere.

The bloom was first reported in Lake George on April 10. It originated in Lake George, then moved northward in the river as far north as County Road 214 between St. Augustine and Palatka, said Dave Whiting, deputy director of the Florida Department of Environmental Protection’s environmental assessment and restoration division. The blooms have been reported by boaters and wildlife commission biologists and detected in water samples and satellite imagery. Both the wildlife commission, DEP and the St. Johns River Water Management District are investigating.

FWC biologists noted the algae bloom on the east side of Lake George while doing a fish study in April. “They were electro-fishing (shocking fish to the surface) and all of the fish that they pulled up were absolutely healthy," Brown said.

On April 25, biologists with the commission's wildlife research institute and fisheries division went to nine locations in Lake George and the surrounding springs and collected samples of fish, she said. Traces of blue-green algae were detected in both Silver Glen and Salt Springs.

"There were scales off and discoloration of the skin in these animals that they took in," said Brown. Although "the visibility was lower and the water looked murky in Salt Springs," she said, there was no visible bloom at Silver Glen and the water was very clear."

At Salt Springs, dead mullet were observed on the banks halfway through the run and one gar was observed near the mouth of the run. They began collecting fish using electro-shock fishing and collected a total of 17 fish, 11 from Silver Glen, including 10 mullet and one tilapia, and six mullet from Salt Springs.

The mullet investigation at Blue Spring State Park may trigger a temporary closing of the park’s spring run on Tuesday. The wildlife commission is scheduled to collect samples, and they do that using the electro-fishing technique that essentially electrocutes the fish, so people can't be in the water.

The FWC hasn’t yet drawn any specific correlation between the lesions and the algae blooms, Brown said.

All of the samples from necropsies of the fish are still being processed, she said, and the results of the testing are pending. Tissue samples from the hearts, livers and kidneys of the fish have to be prepared through a processing of chemicals and placing onto slides, then stained and analyzed, she said.

"It's a long process. Right now we can't speculate on what's going on because we don't have results," she said. That includes linking the spots on the fish in Blue Spring to the fish in Silver Glen or linking the lesions to the algae blooms or any other activities on the river.

A type of freshwater pathogen has previously been reported on mullet, but Brown said no indication of that has been collected during this investigation.

Missy Gibbs, a professor at Stetson University in DeLand and director of the university's aquatic and marine biology program, said she's never seen any thing like it on the mullet at Blue Spring.

"We’ve seen smaller bits of fungus on sunfish, but not on anything else," said Gibbs, who has studied fish in Blue Spring for 20 years.

Water samples during 53 site visits by DEP in the area have shown mixed species of blue-green algae and three different types of toxins produced by the algae, Whiting said. All of the toxins were at “pretty low levels,” he said, either at trace levels or low, and none have tested at concentrations that would meet the levels for human health concerns.

The blue green algae produced toxin microcystin was detected in 14 of 53 samples, he said. The toxins cylindrospermpopsin and saxitoxin were detected 43 times in the 53 site visits.

Blue-green algae, also known as cyanobacteria, is naturally occurring in Florida's waterways, but the incidence and severity of the blooms has increased as nitrogen loading from fertilizers, wastewater and stormwater have increased.

“We are seeing a higher frequency of these types of blooms, as well as they’re being more persistent and intense, and that’s globally, not just in Florida,” Whiting said.

Cyanobacteria are “an ancient life form,” he said. They produce energy by photosynthesis and by taking up nutrients in the water. Dense blooms can cause fish kills or stress out the fish by depleting oxygen.

It's possible the algae blooms have stressed the mullet, leaving them susceptible to parasites or bacterial infections, said Whiting, but they won't know for sure until testing is complete.

Mullet are highly mobile fish and the fish at Blue Spring could have been out in the main St. Johns River, he said.

Last week, officials with the department and the water district toured the river with the St. Johns Riverkeeper. The Riverkeeper, an advocacy group devoted to protecting and restoring the river, has expressed concerns about the toxic blue-green algae blooms that periodically show up in the river, but the concern this year is how early the bloom appeared.

Whiting said water district scientists theorize the blooms may have been prompted by a very wet 2018 followed by a dry spring. The rain created a lot of nutrient-rich runoff in the Lake George basin, he said, but once the water got to the lake the dry period this spring might have meant the nutrient-rich water was just sitting in the lake and not flowing out very quickly.

Cyanobacteria like still, warm water, he said. And they can move around in the water, going higher in the daylight to take advantage of the sun, then moving deeper to get to the layer of nutrients that might be sitting lower in the water.

The blue-green algae blooms in the Fellsmere area have prompted ongoing controversy over the dumping of sludge from wastewater treatment.

Some scientists and advocacy groups, such as the Riverkeeper, have raised alarms about the spreading of biosolids in the river’s watershed, arguing those nutrients are washing off into the river and fueling the toxic algae blooms.

DEP formed a technical advisory committee last year to look into the dumping of biosolids.

Since his inauguration, Gov. Ron DeSantis has stated improving water quality in Florida is one of his priorities. One of his first steps was the announcement of a blue-green algae task force.