Paper Type

Master's Thesis


College of Arts and Sciences

Degree Name

Master of Science in Biology (MS)



NACO controlled Corporate Body

University of North Florida. Department of Biology

First Advisor

Dr. Maria Laura Habegger

Second Advisor

Dr. Brian Wingender

Third Advisor

Dr. Eric Johnson

Department Chair

Cliff Ross

College Dean

Kaveri Subrahmanyam


There is a lack of research describing how widespread environmental changes in marine ecosystems affect wild adult teleost otoliths, limiting our ability to understand the impacts that alterations to otoliths can have on fish physiology and ecology. In this study, morphological and microstructural changes in wild adult fish otoliths were traced over 3 decades among species common in Tampa Bay, Florida – red drum Sciaenops ocellatus and common snook Centropomus undecimalis. Optical microscopy and scanning electron microscopy were used to characterize otolith morphology and microstructure, respectively, to then pair with fluctuations in environmental variables – water temperature, pH, dissolved oxygen (DO), and salinity. Results show that fluctuations in environmental conditions correspond with some changes in otolith morphology and microstructure, though the trends are not clear. Sciaenops ocellatus otolith size increased with age, lower water temperature, lower pH, and lower dissolved oxygen, while otolith density did not correlate with any environmental variables. Centropomus undecimalis otolith size increased with age, and density increased with higher DO, but otherwise was not clearly influenced by any environmental variables. Microstructural features in S. ocellatus otoliths showed some relationships with environmental variables – large pores corresponded with warmer temperatures, small crystals and small pores corresponded with low DO, and small crystals corresponded with low salinity, while small pores and acicular crystals increased over time. In C. undecimalis, irregular crystals corresponded with low DO, and daily rings decreased over time. The lack of significant consistent changes in otolith morphology and microstructure over time could be a result of relatively stable environmental conditions in Tampa Bay over the past few decades. Our results show that minor environmental changes can influence wild adult otolith morphology and microstructure in some ways, but further research is required to determine the physiological and ecological consequences of climate change on otoliths.

Available for download on Friday, July 18, 2025