Graduation Year
2023
Document Type
Thesis
Degree
M.S.
Degree Name
Master of Science (M.S.)
Degree Granting Department
Marine Science
Major Professor
Steven A. Murawski, Ph.D.
Committee Member
Ernst B. Peebles, Ph.D.
Committee Member
Julie L. Vecchio, Ph.D.
Keywords
isoscape, ontogeny, spatial movement, trophic position
Abstract
Spatial geography, ontogenetic movement, and trophic patterns of mobile species are key elements of effective marine resource management. A number of methods are currently available for tracking movements of pelagic migratory species, including the use of conventional and electronic tags. However, tagging campaigns can take years to provide useful data, can be expensive, and only capture a portion of a fish’s lifetime. For this project, I used stable-isotopic ratios of nitrogen (δ15N) and carbon (δ13C) in metabolically inert, chronologically-layered fish-eye lenses to explore lifetime movement and trophic patterns of yellowfin tuna (Thunnus albacares) and blackfin tuna (Thunnus atlanticus) in the Gulf of Mexico (GoM). In both species, the δ13C values had a weak relationship with eye-lens diameter, reflecting a change in basal resource from cross-shelf movement. The δ15N values were strongly correlated with eye-lens diameter, suggesting trophic growth and movement from areas with low δ15N values to areas with high δ15N values. Correlation between δ15N and δ13C was weak overall for both species, but some individual profiles displayed moderate to strong correlations that indicate alternate periods of migration and residency. Additionally, δ13C values in the innermost laminae of yellowfin tuna were generally lower than the values in blackfin tuna, suggesting that spawning areas for these two species may be distinct. Despite the movement displayed in the profiles, the isotopic values were consistent with ranges previously measured in the GoM, so neither species appeared to exit the GoM. These results demonstrate that stable-isotopic ratios in eye lenses can be used successfully on pelagic fishes to determine broad life-history patterns.
Scholar Commons Citation
Rullo, Kylee M., "Stable Isotope Analysis on Yellowfin and Blackfin Tuna Eye Lenses Reveals Life History Patterns in the Gulf of Mexico" (2023). USF Tampa Graduate Theses and Dissertations.
https://digitalcommons.usf.edu/etd/10084
