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Episode Show Notes
Dr. Jennifer Rehage is a fisheries scientist at Florida International University (FIU) who runs a fisheries lab studying the health of South Florida waterways including Biscayne Bay and the Everglades. Carissa Gervasi is a PhD student working with Dr. Rehage, conducting research on fish species including jack crevalle, bonefish, permit, and tarpon, as well as studying the effects of pharmaceuticals on aquatic life. In this episode, they reveal how medications from your medicine cabinet are changing fish behavior in South Florida, why bonefish are incredibly picky about where they hang out, and what seven years of research has uncovered about the resilience and sensitivity of fish in degraded ecosystems. If you fish Biscayne Bay or the Everglades, this conversation will change how you think about the water you're standing in.
What is the FIU Fisheries Lab studying in South Florida?
The FIU Fisheries Lab, directed by Dr. Jennifer Rehage in the Department of Biological Sciences, focuses on fish ecology, fish physiology, population dynamics, and the general health of South Florida ecosystems including Biscayne Bay and the Everglades. They work on gamefish species such as tarpon, permit, bonefish, and jack crevalle, studying habitat use, life history, and the effects of anthropogenic stressors like water quality and pharmaceutical pollutants.
Who is Dr. Jennifer Rehage?
Dr. Jennifer Rehage is the Director of the Fisheries Lab at Florida International University. She completed her undergraduate degree at University of Florida, earned her PhD at the University of Georgia studying larval fish ecology in the context of habitat restoration, completed a postdoc at UC Davis, and started the Fisheries Lab at FIU in 2013.
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How Pharmaceuticals Are Changing Fish Behavior in Biscayne Bay
Carissa Gervasi's PhD research focuses on something most anglers never think about when they wade the flats: the medications flushed into South Florida's waterways are altering how fish behave. People use medications like antidepressants and antihistamines, then excrete them or dispose of them improperly. These pharmaceuticals make it through wastewater treatment plants because many facilities don't completely remove them. The treated wastewater released into the environment still contains these compounds, and fish are swimming in it. Carissa explains how these medications can increase aggression and boldness in fish, change feeding behavior, and affect predator avoidance. The implications go beyond individual fish behavior to entire ecosystem dynamics and predator-prey relationships. Carissa breaks down how pharmaceuticals enter the water and what they're finding in fish tissue starting at 7:23.
Why Jack Crevalle Are the Perfect Research Subject
If you've ever hooked a jack crevalle, you know they're incredibly strong, fast, and aggressive fish. But Carissa chose them for her research for reasons that go deeper than their fighting ability. Jack crevalle are incredibly adaptable to different habitats and water conditions, making them ideal for studying how fish respond to environmental stressors. They're also very mobile, migrating between different habitats to find food and optimal conditions. The lab has tagged jack crevalle to track their movement patterns, revealing that these fish cover large distances and don't just stay in one spot. Carissa's work is uncovering how jack crevalle use South Florida's interconnected waterways and how pharmaceutical exposure might be changing their behavior in ways that ripple through the food web. The conversation about jack crevalle as both predators and research subjects kicks off at 2:45.
Hear Dr. Rehage and Carissa explain how they catch and study fish in the field
Bonefish, Tarpon, and the Acoustic Telemetry Arrays Tracking Their Movements
The FIU Fisheries Lab has established acoustic telemetry arrays in Biscayne Bay and the Florida Keys to track bonefish and tarpon movements. Jennifer explains that bonefish are incredibly sensitive to changes in their environment, responding to water temperature, salinity, and other factors by relocating to better habitat when conditions become unfavorable. They're fussy fish that are very particular about where they are and the conditions they're in. Tarpon research reveals a complex life history where juvenile fish use nursery habitats like mangroves and shallow coastal areas, then move to different habitats as they grow, eventually reaching offshore areas. This life history strategy allows tarpon to find the best food, shelter, and conditions for their size and stage of development. The tagging data is revealing migration patterns that have major implications for how we manage and protect these gamefish. Jennifer explains what they're learning from acoustic tagging of bonefish and tarpon at 13:40.
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SubscribeThe Biggest Threats Facing Biscayne Bay and the Everglades
When Tom asks about the biggest challenge facing South Florida's waters, Jennifer doesn't hesitate: water quality and quantity. The Everglades historically had a very different hydrology than today, with water flowing from Lake Okeechobee south through the Everglades to Florida Bay. Now water is being diverted for agricultural and urban use, and the natural flow has been severely altered, causing massive impacts on the ecosystem. Biscayne Bay is experiencing algal blooms, seagrass loss, and impacts on fish populations driven by nutrient pollution, reduced light, and changes in hydrology. Jennifer notes that while there have been some improvements in certain areas, overall the trends are not moving in the right direction. The solutions require improving water quality by reducing nutrient pollution, restoring natural water flows in the Everglades, reducing pharmaceutical pollution, and managing human activities to reduce ecosystem impacts. Jennifer's assessment of what's happening in Biscayne Bay and the path forward starts at 17:23.
This conversation goes deep into the science behind South Florida's fisheries.
Essential listening for anyone who fishes these waters.
Key Takeaways
- • Pharmaceuticals from treated wastewater are making it into South Florida's waterways and changing fish behavior in ways that affect entire ecosystems
- • The FIU Fisheries Lab uses field sampling with gill nets, seines, and hook and line combined with laboratory experiments to understand how stressors affect fish
- • Bonefish are incredibly sensitive to environmental changes and will relocate when water temperature, salinity, or other conditions become unfavorable
- • Tarpon use different habitats throughout their life cycle, starting in mangroves and shallow coastal nurseries before moving offshore as they grow
- • Water quality and quantity represent the biggest challenge for the Everglades, where natural water flows have been severely altered from agricultural and urban diversion
- • Dr. Rehage's coolest discovery after seven years of research: fish are simultaneously incredibly resilient and incredibly sensitive depending on the stressor
- • Jack crevalle are highly mobile fish that migrate between habitats and cover large distances, making them ideal subjects for studying fish responses to environmental changes
Final Thoughts from Tom
I love conversations like this one. Jennifer and Carissa are doing work that matters, and they're 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 fish, tagging fish, and getting their hands dirty to understand what's really happening in South Florida's ecosystems.
The pharmaceutical research is eye-opening. I had no idea that medications were making it through treatment plants and into the water where we fish. The fact that these compounds are changing fish behavior—making them more aggressive, altering their feeding patterns—that has implications we're just beginning to understand. And when you combine that with the water quality issues in Biscayne Bay and the Everglades, it's clear we've got serious challenges ahead.
But here's what gives me hope: people like Jennifer and Carissa are figuring this stuff out. They're identifying the problems, understanding the mechanisms, and working toward solutions. If you fish South Florida, if you care about these waters, this conversation is worth your time. Listen to the whole thing.
Frequently Asked Questions
What is the FIU Fisheries Lab?
The FIU Fisheries Lab is a research facility at Florida International University directed by Dr. Jennifer Rehage that focuses on fish ecology, physiology, population dynamics, and ecosystem health in South Florida. The lab studies gamefish like tarpon, bonefish, permit, and jack crevalle in Biscayne Bay and the Everglades.
How do pharmaceuticals get into South Florida waters?
Pharmaceuticals enter waterways when people use medications and then excrete them or dispose of them improperly. These compounds make it to wastewater treatment plants, and many plants don't completely remove all pharmaceuticals, so treated wastewater released into the environment still contains these medications.
What effects do pharmaceuticals have on fish?
Research at the FIU Fisheries Lab shows that pharmaceutical pollutants can cause changes in fish behavior including increased aggression and boldness, altered feeding behavior, and changes in predator avoidance. These behavioral changes can affect predator-prey dynamics, competitive interactions, and overall ecosystem function.
What is the biggest threat to the Everglades ecosystem?
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 being diverted for agricultural and urban use, severely altering the natural flow and causing massive ecosystem impacts.
How does the FIU Fisheries Lab study fish movement?
The lab uses acoustic telemetry arrays in Biscayne Bay and the Florida Keys to track fish movements. They tag fish with acoustic transmitters and use receiver stations to monitor where fish go, revealing movement patterns, habitat use, and how fish respond to environmental conditions.
Related Episodes
More insights into the gamefish species that Dr. Rehage and Carissa study using acoustic telemetry
Deep dive into the water quality and quantity challenges affecting South Florida's ecosystem
Understanding the algal blooms, seagrass loss, and fish population impacts discussed in this episode
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Shop GORUCKDr. Jennifer Rehage – Director of the Fisheries Lab, Florida International University
Carissa Gervasi – PhD Student, FIU Fisheries Lab
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Dr. Jennifer Rehage & Carissa Gervasi
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 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, with research focusing on jack crevalle, bonefish, permit, tarpon, and the effects of pharmaceutical pollutants on aquatic life. Together they study fish populations in Biscayne Bay and the Everglades using field sampling and laboratory experiments.
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