Date of Award

Spring 5-2022

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)


Ocean Science and Engineering

Committee Chair

Dr. Frank Hernandez

Committee Chair School

Ocean Science and Engineering

Committee Member 2

Dr. Chet Rakocinski

Committee Member 2 School

Ocean Science and Engineering

Committee Member 3

Dr. Simon Geist


The Gulf of Mexico is an important early life habitat for billfishes, whose larvae experience high growth rates despite having highly specialized diets, limited foraging abilities, and oligotrophic offshore habitats. Variability in the recent growth of sailfish larvae was compared to environmental, spatial, diet, prey availability, and fatty acid metrics using data collected from near-surface waters in the northern Gulf of Mexico (2017 - 2019). Larvae exhibited a highly selective feeding strategy in early development and expanded their feeding niche to include larger prey items (calanoid copepods, larval fish) once they reached flexion. Sailfish larvae showed significant positive selection for Evadne and female Farranula. To examine quality of preferred prey and condition of sailfish larvae, fatty acid concentrations were examined as fatty acid methyl esters. Results indicated that total fatty acid concentration of preferred prey was highest closest to shore with a trend for lower total fatty acid concentration further offshore. Additionally, Evadne had lower DHA% and higher AA% than did Farranula or Corycaeus. While DHA%, EPA%, and AA% increased in the tissue of sailfish larvae with ontogeny, total fatty acid remained consistent. Recent larval growth was estimated by otolith increment analysis and was higher when more prey were consumed, when dissolved oxygen concentrations were greater, and when larvae were found in anticyclonic boundary regions. This is the first study to examine and report sex-specific selection of zooplankton prey by sailfish larvae, and to examine the fatty acids of sailfish larvae and their preferred prey.

ORCID ID 0000-0002-0130-6023