Dr. Jennifer Rehage, a professor and marine ecologist at Florida International University (FIU), along with researcher Carissa Gervasi, return to reveal shocking new findings from their Jack Crevalle acoustic tagging study in South Florida coastal systems. When fishing guides in the Florida Keys raised concerns about declining catch rates, these researchers tagged fish with acoustic transmitters to track their movements—and discovered migration patterns that stunned everyone. Fish tagged in the Keys showed up in Tampa, then Apalachicola, and finally Louisiana—distances no one anticipated. This episode explores what these findings mean for anglers, conservation, and multi-state fisheries management, and why citizen science from the fishing community is critical to understanding coastal fish populations.
What Did FIU's Jack Crevalle Study Discover About Fish Movement?
The FIU Jack Crevalle acoustic tagging study discovered that fish tagged in the Florida Keys migrated all the way to Louisiana, traveling through Tampa and Apalachicola—a distance researchers never anticipated. This finding was made possible through collaborative receiver networks including the FACT network and iTag network, where acoustic tags surgically implanted in fish ping when swimming near underwater receivers positioned along the coast.
Who is Dr. Jennifer Rehage?
Dr. Jennifer Rehage is a professor at Florida International University and a marine ecologist specializing in fish migration and habitat use in South Florida coastal systems. She works alongside researcher Carissa Gervasi leading the Jack Crevalle acoustic tagging study to understand population dynamics and migration patterns of this important coastal species.
This episode is brought to you by Star brite, the marine care products that researchers like Dr. Rehage and Tom rely on to keep their boats and equipment ready for long days on the water studying fish populations.
When Fishing Guides Sound the Alarm: The Origin of the Jack Crevalle Study
The entire Jack Crevalle research project began because Florida Keys fishing guides noticed something troubling—declining catch rates that didn't match their decades of experience on the water. These guides, who spend more time observing fish behavior than almost anyone, reached out to FIU with concerns that Jack Crevalle populations might be in trouble. Dr. Rehage and Carissa Gervasi responded by launching an acoustic tagging study, surgically implanting small transmitters in Jack Crevalle to track their movements through existing receiver networks. What they discovered would completely reshape understanding of how these fish use coastal habitats—but it started with guides paying attention and scientists willing to listen. The conversation about how fishing guides sparked this groundbreaking research begins early in the episode.
From the Keys to Louisiana: The Migration Nobody Expected
When Dr. Rehage and Carissa first started detecting tagged Jack Crevalle moving north from the Florida Keys to Tampa, it was notable but not shocking. When those same fish pinged receivers in Apalachicola, eyebrows went up. But when the data showed fish continuing all the way to Louisiana, it fundamentally changed everything researchers thought they knew about Jack Crevalle movement patterns. Tom points out what every angler has observed—there are certain times of year when you see bigger fish or more fish, and other times when they seem to disappear. This discovery explains why: the fish simply weren't there because they were hundreds of miles away. The implications for how we manage and protect these populations span multiple states and jurisdictions. The full story of this unprecedented migration discovery and what it means for anglers starts midway through the episode.
Hear Dr. Rehage explain how collaborative receiver networks made this discovery possible
How Acoustic Tags and Receiver Networks Track Fish Across State Lines
The technology behind this research sounds like something from a spy thriller, but it's elegantly simple. Acoustic tags are small transmitters surgically implanted in fish that emit unique signals. When a tagged fish swims within range of an underwater receiver—essentially a listening station anchored to the bottom—the receiver logs the detection with a timestamp. The genius is in the collaboration: the FACT network and iTag network consist of receivers positioned along the entire Gulf Coast, maintained by different research institutions who share their data. This means a fish tagged in the Keys by FIU can be detected by a receiver in Louisiana maintained by a completely different university, and everyone benefits from the shared information. It's this cooperative infrastructure that made the Jack Crevalle migration discovery possible without needing to deploy hundreds of new receivers. The technical details of how these tags work and what information they capture are explained in detail during the episode.
Get the Best Fishing & Outdoor Content
Weekly insights on fishing strategy, conservation, and the disciplines that transfer across pursuits.
SubscribeWhat This Means for Conservation and Management Across Multiple States
Tom asks the question every angler wants answered: if Jack Crevalle are traveling from the Florida Keys to Louisiana, what does this mean for regulations, size limits, and conservation efforts? The answer is more complex than anyone anticipated. When fish populations cross state lines, management decisions made in Florida directly affect the fish anglers encounter in Alabama, Mississippi, and Louisiana. The researchers discuss how this discovery calls for multi-state coordination in conservation efforts—something that's challenging to implement but critical for protecting these populations. They also emphasize the role of citizen science, explaining how anglers who report tagged fish sightings or participate in catch-and-release programs contribute invaluable data points that fill gaps between receiver stations. The questions explored—what time of year fish were captured versus detected, whether these are Keys fish moving seasonally or different populations mixing, and how anglers can actively help the research—paint a picture of fisheries science that depends on collaboration between researchers and the fishing community. The full discussion of management implications and how anglers can contribute to the research unfolds later in the conversation.
Don't miss this one.
A conversation that changes how you think about coastal fish populations.
Key Takeaways
- • Florida Keys fishing guides noticed declining Jack Crevalle catch rates and partnered with FIU researchers to investigate—proving that on-the-water observations from experienced anglers can drive groundbreaking science
- • Jack Crevalle tagged in the Florida Keys traveled to Tampa, Apalachicoa, and all the way to Louisiana—migration distances that surprised even the researchers and explain why fish seem to appear and disappear seasonally
- • Acoustic tag technology and collaborative receiver networks like FACT and iTag enable long-distance fish tracking without new infrastructure, with tagged fish pinging underwater listening stations as they swim past
- • Multi-state migration patterns mean conservation decisions in one state directly impact fish populations in others, requiring unprecedented coordination between fisheries managers across the Gulf Coast
- • Citizen science from anglers who report tagged fish and participate in catch-and-release programs provides critical data points that fill gaps between receiver stations and help researchers understand population dynamics
- • The questions still being explored—seasonal timing, whether these are the same fish or different populations, and practical applications for regulations—show that this research is ongoing and anglers can actively contribute
Final Thoughts from Tom
This conversation with Dr. Rehage and Carissa reminds me why I love bringing researchers on the show. They're answering questions that every guide and serious angler has wondered about—where do the fish go when they're not here? The fact that Jack Crevalle are traveling from the Keys all the way to Louisiana changes how we need to think about these populations. It's not just a Florida fish or a Louisiana fish; it's a Gulf-wide species that needs Gulf-wide management.
What really struck me was how much this research depends on guides and anglers paying attention and being willing to share what they're seeing. The entire study started because guides in the Keys noticed something was off with their catch rates. That partnership between the fishing community and scientists is how we're going to protect these fisheries for the next generation.
If you fish for Jacks anywhere in the Gulf, or if you're just interested in how cutting-edge fisheries science actually works, this episode is absolutely worth your time. Listen to the whole thing.
Frequently Asked Questions
How far do Jack Crevalle migrate?
Jack Crevalle tagged in the Florida Keys have been detected traveling to Tampa, Apalachicola, and as far as Louisiana—distances that researchers did not anticipate before starting the acoustic tagging study. This migration spans multiple state jurisdictions across the Gulf Coast.
What are acoustic tags and how do they work?
Acoustic tags are small transmitters surgically implanted in fish that emit unique signals. When the tagged fish swims near underwater receivers positioned along the coast, the receiver logs the detection with a timestamp, allowing researchers to track fish movements over long distances through collaborative networks like FACT and iTag.
Why did FIU start studying Jack Crevalle?
The Jack Crevalle study began because fishing guides in the Florida Keys raised concerns about declining catch rates. These experienced guides noticed patterns that didn't match their historical observations, prompting FIU researchers to investigate through acoustic tagging to understand population dynamics and movement patterns.
How can anglers help with Jack Crevalle research?
Anglers can contribute valuable data by reporting tagged fish sightings and participating in catch-and-release programs. These citizen science contributions provide critical data points that fill gaps between receiver stations and help researchers understand Jack Crevalle population dynamics and seasonal movements.
What does Jack Crevalle migration mean for fisheries management?
Since Jack Crevalle migrate across multiple states from Florida to Louisiana, management decisions in one state directly affect fish populations in others. This discovery calls for multi-state coordination in conservation efforts and regulations, as these fish are not confined to a single jurisdiction's waters.
Related Episodes
Dr. Rehage's previous appearance discussing FIU's broader fisheries research in South Florida coastal systems
Guides share firsthand observations about catch rates and seasonal patterns that inform scientific research
Deep dive into the technology and collaborative networks that make long-distance fish tracking possible
Exploring the critical role of citizen science and angler observations in fisheries management
Sponsors
Keep your boat and equipment research-ready with Star brite's trusted marine care products.
Shop Star britePremium pliers and tools built for serious anglers who demand reliability on the water.
Get Danco GearFuel your long days on the water with premium supplements trusted by athletes and anglers.
Shop 1st PhormPerformance nutrition designed for hunters and anglers who push their limits outdoors.
Shop MTN OPSMilitary-grade gear built to withstand the toughest conditions on and off the water.
Get GORUCKDr. Jennifer Rehage - Professor and marine ecologist at Florida International University
Carissa Gervasi - Researcher at Florida International University
Tom Rowland - Host, Tom Rowland Podcast
Download the Tom Rowland Podcast Knot Guide — essential knots every angler should know.
Dr. Jennifer Rehage & Carissa Gervasi
Dr. Jennifer Rehage is a professor at Florida International University (FIU) and marine ecologist specializing in fish migration and habitat use in South Florida coastal systems. Carissa Gervasi is a researcher also at FIU working alongside Dr. Rehage on fish movement and tracking studies. Together they lead the Jack Crevalle acoustic tagging study to understand population dynamics and migration patterns of this important coastal species. Their work exemplifies the power of collaboration between academic researchers, fishing guides, and the angling community to answer critical questions about coastal fisheries. Learn more about their research at Florida International University - FIU Marine Sciences.
Listen or watch on your favorite platform:
