Chris Crowder is a 2025 Florida Sea Grant Guy Harvey Fellow. He is a Ph.D. candidate in integrative and conservation biology at the University of Central Florida. He joined Florida Sea Grant as a 2024 graduate research fellow for his work in Dr. Geoffrey Cook’s Marine Ecology and Conservation Lab in UCF’s Biology Department.
Crowder holding a Sheepshead in Mosquito Lagoon. Image by Chris Crowder.
When biology students are first introduced to the scientific method, they’re often encouraged to observe the natural world and ask, “Why is it that way?” From there, the process typically involves background reading, collecting data, and performing data analysis to uncover possible answers. My current research followed that exact trajectory: it began with a field observation and ended with a mountain of data.
From 2019 to 2021 I was scaring baby fish at Ball State University to understand how simulated predation risk may impact the behaviors of embryonic and larval prey fish. After this, I was fortunate to join Dr. Geoffrey Cook’s Marine Ecology and Conservation Lab at the University of Central Florida. During the first year of my PhD, the lab was conducting fish sampling in Mosquito Lagoon, part of the larger Indian River Lagoon system. I noticed something intriguing: one sample site on an oyster reef had an abundance of fish, while another site just 50 feet away had very few. I wanted to understand what could cause such stark variation in fish abundance over such a small distance.
Healthy fish habitat, like oyster reefs, is the foundation of a healthy fishery. Florida’s fisheries can support a variety of recreational activities for diverse groups of individuals while simultaneously benefiting the local and state economies. Ensuring the sustained production of these ecosystem services and recreational opportunities for future generations will require a better understanding of benthic habitat and broader environmental pressures across multiple trophic levels of fish and spatiotemporal scales.
Crowder presenting research results at the 2024 Ocean Sciences Conference in New Orleans, LA. Image by Chris Crowder.
It’s challenging to pin down exactly what attracts or repels fish from a specific location. Factors like water temperature, salinity, habitat type, or prey availability all play a role. But fish may also respond to conditions not immediately visible at the time and place of sampling. I had to ask: Are the fish here because of something they like? Are they avoiding something they don’t like? Or are they here simply by chance? Gaining insight into these questions can advance our understanding of how environmental factors, prey species, and predator species interactions change throughout time and space.
To answer these questions, I turned to several state agencies for help. I have collaborated with the FWC Fish and Wildlife Research Institute’s Fisheries-Independent Monitoring (FIM) Program which has fish community monitoring data that is truly unmatched in terms of data quality protocols as well as spatial and temporal coverage. I selected several sport fish taxa that were relatively common and are a favorite amongst sportfishers: Snook, Snapper, Trout, Red Drum, and Crevalle Jack. I then selected the top 9 prey taxa representing approximately 80% of the fish diet from the sport fish. I then combined the FIM data with habitat data from the Southwest Florida Water Management District for Tampa Bay and the St. John’s River Water Management District for the Indian River Lagoon.
Ensuring the sustained production of these ecosystem services and recreational opportunities for future generations will require a better understanding of benthic habitat and broader environmental pressures across multiple trophic levels of fish and spatiotemporal scales.
Crowder during fish field sampling in the Indian River Lagoon. Image by Chris Crowder.
I then divided Tampa Bay and the Indian River Lagoon into spatial units—or “spatial complexes”—designed to capture meaningful ecological variation within each spatial complex. These were based on habitat distribution, natural and human-made features (such as bridges and inlets), and the typical daily movement range of my target predator fish species.
For data analysis, I use Bayesian statistics which is a form of statistics that describes your results through detailed probabilities of observing a particular range of results. This can be helpful when dealing with a wide range of unknowns or when describing abundance that can vary greatly – like with fish. I created 396 statistical models which combined 12 years of habitat data and over 20,000 FIM samples representing over 15 million fish. Each model represents a different hypothesis on how environmental factors, space, and prey abundance may influence absence and abundance for each of my species of interest for Tampa Bay and the Indian River Lagoon. These models are complex and require a specialized computer to be built in order to be completed. The results from the Bayesian models are a long list of numbers… a very long list. The results from only the “best” models are a list of numbers about 1 terabyte in size. My results show that prey and predator fish are influenced by different combinations of factors and the same fish between Tampa Bay and the Indian River Lagoon prefer different environmental conditions.
I find the combination of math, fish, and the broader environment fascinating. I have really enjoyed completing this work knowing how my results can inform any different topics. The results from this study could yield a more predictive understanding of prey and predator fish dynamics; and provide insight to better inform wildlife managers, habitat management, stock assessments, and restoration efforts which are tailored to each study taxa and system. I hope the results from my project will ensure a healthy future of ecologically and economically important fish species on Florida’s coasts.
As a PhD student, I have enjoyed making an observation that subsequently has taken me on a rollercoaster of a scientific journey while creating new collaborations, colleagues, and knowledge along the way. The fish in Florida are very special. I hope my work has a positive impact on the long term health of Florida’s fish populations, the coastal habitat, and preserving enjoyment of the community’s relationship to these special resources.
Special thank you to the Guy Harvey Ocean Foundation and Florida Sea Grant in their support of this work. Thank you to the FWRI FIM team and the Southwest Florida Water Management District and the St. Johns River Water Management District for their collaboration and data support.
