FORT LAUDERDALE, Fla. — Redfish, one of the most popular and delicious inshore gamefish in Florida, are contaminated with pharmaceuticals throughout the state, a study by Florida International University and the Bonefish & Tarpon Trust has revealed.
The research states that pharmaceuticals enter bays and estuaries through wastewater discharge, sewage leaks and spills, and seepage from septic tanks.
Ninety-four percent of the redfish sampled had pharmaceuticals in their systems, and 26% had concentrations in their blood that researchers consider to be “concerning.”
The paper said the fish are exposed to the drugs both through passing water over their gills, and by eating prey, such as shrimp and crabs, that have been exposed.
The researchers sampled a total of 113 redfish in the summer of 2022 in nine estuaries throughout the state, taking muscle and blood plasma samples and analyzing them for 94 pharmaceuticals. The estuaries included waters in Florida Bay, Northern Indian River Lagoon, Pensacola, Apalachicola, Cedar Key, Tampa Bay, Charlotte Harbor, St. Augustine and Jacksonville.
Fish from all the estuaries had drugs in their blood, with each fish carrying an average of 2.1 drugs.
Seven of the 113 sampled fish had no drugs in their system at all. Twenty-five percent of the fish had pharmaceutical levels beyond what researchers considered safe, that is, they had concentrations greater than one-third of the dose considered therapeutic to humans.
“Given the impacts of many of these pharmaceuticals on other fish species and the types of pharmaceuticals found, we are concerned about the role pharmaceuticals play in the health of our fisheries,” said Dr. Jennifer Rehage, FIU professor and the study’s lead researcher.
The estuaries with the highest number of pharmaceuticals were Apalachicola and Tampa Bay, with around three per fish.
Charlotte Harbor, Cedar Key, Pensacola, St Augustine and Jacksonville formed the middle of the pack, with around two per fish, while Florida Bay and the Indian River Lagoon had the fewest number of drugs per fish (0.9).
The drugs in question
Rehage and her team found cardiovascular medications, opioid pain relievers and psychoactive medications in the redfish’s blood systems.
More than 50% of the redfish sampled were contaminated with both flecainide, which in humans slows electrical signals in the heart to stabilize heart rhythms, and the habit-forming opioid pain reliever tramadol.
The researchers also detected flupentixol, which is used to treat schizophrenia and psychosis, at above safe levels in 20% of the redfish sampled. Caffeine was also quite common, found in 43% of the fish.
Currently, wastewater treatment plants are unable to remove pharmaceuticals from wastewater — any breach of the system would release pharmaceuticals into the ecosystem. Additionally, septic systems in low-lying areas are becoming susceptible to sea level rise.
The drug represent a threat to redfish and possibly other species.
In previous studies, eight of the drugs found in Florida redfish were harmful to other fish. Tramadol is of particular concern, as it delays hatching and increases boldness and asocial behaviors in fish.
Caffeine causes fish to explore less and move erratically. It can also cause skeletal deformations. Other drugs found in the redfish induce aggression and muscle weakness, and cause tissue damage, and suppress escape reflexes and reduce fertility. In other words, the stuff we flush down the toilet can become a stew of potential problems in the fish’s bloodstream.
She’s particularly concerned about the vast unknown of drug interactions within the fish. “The fish don’t have a choice. They’re exposed to as many as five drugs.”
Rehage said that in preliminary studies of prey items such as shrimp and crabs indicate high pharmaceutical levels in their flesh, meaning other species, such as snook and seatrout, are ingesting the drugs as well. She has not studied those species yet, but they have a similar diet to redfish.
In a earlier FIU study, Rehage and her team found a cocktail of pharmaceuticals in bonefish in Biscayne Bay and the Florida Keys. That study covered three years, and found an average of seven drugs in the 93 fish they sampled.
What is the risk to humans?
You would have to eat 48,000 redfish filets to consume a full dose of haloperidol, the schizophrenia/ psychosis treatment that had the highest concentration levels found in this study.
In essence, pharmaceuticals were much less present in redfish muscle tissue than in blood. Just more than 38% of the 109 muscle samples contained drugs.
The three most common in muscle tissue were opioid pain reliever tramadol, the heart medicine flecainide and haloperidol. Concentration of these drugs in muscle tissue were very low, said the study.
Some good news for the east coast fish — researchers didn’t find any drugs in muscle tissue of redfish in the Indian River Lagoon.
What can be done
Kellie Ralston, Bonefish Tarpon Trust’s vice president for conservation and public policy, said in a release that though Florida is making efforts to convert septic systems to sewage treatment, “there are additional opportunities for improvement by retrofitting existing wastewater treatment plants with innovative technologies, like ozone treatment, to remove pharmaceuticals and requiring such technology on new wastewater facilities.”
According to a 2018 paper in the journal Science Direct, ozonation leads to an oxidation process that causes compounds commonly found in pharmaceuticals to biodegrade and break down more quickly. Once broken down, they no longer react with the ecosystem, including fish, in a harmful way.
It’s not a perfect system. Some toxic by-products can result, according to the 2018 study, requiring additional treatment.
The ozone process is only possible through sewage treatment plants, not septic.
According to the study, the U.S. accounts for 5% of the world’s population but consumes half of the world’s pharmaceutical production.
“This is a new dimension of water quality,” said Rehage. “It’s sort of invisible. We don’t see it ... but we’re getting medicated all around us, and we’re medicating our wildlife that we care about.”
