The health of South Florida's fisheries depends on science most anglers never think about, and Dr. Jennifer Rehage and Carissa Gervasi of Florida International University spend their days in the water studying it. Dr. Rehage directs the FIU Fisheries Lab, and Gervasi is a PhD student researching jack crevalle, bonefish, permit, tarpon, and the effects of pharmaceuticals on aquatic life. In this conversation they explain how medications from your medicine cabinet are changing fish behavior, what acoustic telemetry reveals about bonefish and tarpon, and the biggest threats facing Biscayne Bay and the Everglades.
Watch the full conversation on YouTube or listen to the episode now.
The FIU Fisheries Lab, directed by Dr. Jennifer Rehage, focuses on fish ecology, physiology, population dynamics, and the general health of South Florida ecosystems including Biscayne Bay and the Everglades. They study gamefish such as tarpon, permit, bonefish, and jack crevalle, looking at habitat use, life history, and the effects of stressors like water quality and pharmaceutical pollutants.
Pharmaceuticals enter waterways when people use medications and then excrete them or dispose of them improperly. These compounds reach wastewater treatment plants, and many plants do not completely remove all pharmaceuticals, so the treated wastewater released into the environment still contains these medications, which fish are then swimming in.
Research at the FIU Fisheries Lab shows that pharmaceutical pollutants can change fish behavior, including increased aggression and boldness, altered feeding behavior, and changes in predator avoidance. Carissa explains that these behavioral changes can ripple through predator-prey dynamics, competitive interactions, and overall ecosystem function.
According to Dr. Jennifer Rehage, the biggest threat is water quality and quantity. Water that historically flowed from Lake Okeechobee south through the Everglades to Florida Bay is now diverted for agricultural and urban use, severely altering the natural flow and causing massive ecosystem impacts, alongside algal blooms and seagrass loss in Biscayne Bay.
The lab uses acoustic telemetry arrays in Biscayne Bay and the Florida Keys to track fish movement. They tag fish with acoustic transmitters and use receiver stations to monitor where the fish go, which reveals movement patterns, habitat use, and how fish respond to changing environmental conditions.
Carissa chose jack crevalle because they are incredibly adaptable to different habitats and water conditions, which makes them ideal for studying how fish respond to environmental stressors. They are also highly mobile, migrating between habitats and covering large distances, so tagging them reveals how they use South Florida's interconnected waterways.
I love conversations like this one because Jennifer and Carissa are doing work that matters, and they are doing it with their boots in the water. Too often fisheries science feels disconnected from the actual fishing experience, but these two are out there catching, tagging, and getting their hands dirty to understand what is happening in South Florida's ecosystems. I wanted them on because the pharmaceutical research is genuinely eye-opening, and because the people figuring this stuff out give me real hope for these waters.
Carissa's PhD research focuses on something most anglers never consider: medications flushed into South Florida's waterways are altering how fish behave. People use antidepressants and antihistamines, then excrete them or dispose of them improperly, and many wastewater plants do not completely remove the compounds, so treated water still contains them. Carissa explains how these medications can increase aggression and boldness, change feeding behavior, and affect predator avoidance. Hear what they are finding in fish tissue in the episode.
If you have ever hooked a jack crevalle, you know they are strong, fast, and aggressive, but Carissa chose them for reasons deeper than their fight. Jacks are incredibly adaptable to different habitats and conditions, which makes them ideal for studying how fish respond to stressors, and they are highly mobile, migrating between habitats and covering large distances. The lab has tagged them to track movement, revealing how they use the interconnected waterways. Listen to her explain jacks as both predators and research subjects.
Watch the full episode or listen now to hear the rest.
The lab has established acoustic telemetry arrays in Biscayne Bay and the Florida Keys to track bonefish and tarpon. Jennifer explains that bonefish are incredibly sensitive to their environment, relocating when temperature, salinity, or other conditions become unfavorable, which makes them fussy and particular. Tarpon show a complex life history, using mangrove nurseries as juveniles before moving offshore as they grow. The tagging data has major implications for managing these gamefish. Hear what they are learning.
When I asked about the biggest challenge facing South Florida's waters, Jennifer did not hesitate: water quality and quantity. The Everglades historically had water flowing from Lake Okeechobee south to Florida Bay, but diversion for agriculture and urban use has severely altered the natural flow. Biscayne Bay is experiencing algal blooms, seagrass loss, and impacts on fish from nutrient pollution. The solutions require reducing nutrient and pharmaceutical pollution and restoring natural flows. Hear her assessment and the path forward.
The day after this one, the pharmaceutical research was still on my mind. I had no idea that medications were making it through treatment plants and into the water where we fish, or that these compounds are changing fish behavior in ways we are just beginning to understand.
But here is what gives me hope: people like Jennifer and Carissa are figuring this stuff out. They are identifying the problems, understanding the mechanisms, and working toward solutions. If you fish South Florida or care about these waters, this conversation is worth your time. Listen to the whole thing.
Listen to the entire conversation here.
The Tom Rowland Podcast brings you long-form conversations with the most accomplished anglers, hunters, conservationists, and outdoor professionals in the game. Listen to every full-length Tom Rowland Podcast interview.
Dr. Jennifer Rehage is a fisheries scientist and the Director of the Fisheries Lab in the Department of Biological Sciences at Florida International University. She earned her undergraduate degree at the University of Florida, her PhD at the University of Georgia studying larval fish ecology in habitat restoration, and completed postdoctoral work at UC Davis before starting the FIU lab in 2013. Carissa Gervasi is a PhD student at FIU working with Dr. Rehage on fish ecology and physiology, focusing on jack crevalle, bonefish, permit, tarpon, and the effects of pharmaceutical pollutants. Together they study fish populations in Biscayne Bay and the Everglades using field sampling and laboratory experiments.
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