TROPHIC ECOLOGY OF SAILFISH LARVAE IN THE GULF OF MEXICO: AN ANALYSIS OF DIET, PREY AVAILABILITY, PREY QUALITY, AND INFLUENCES ON LARVAL GROWTH

<p>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 <em>Evadne</em> and female <em>Farranula.</em> 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, <em>Evadne</em> had lower DHA% and higher AA% than did <em>Farranula</em> or <em>Corycaeus. </em>While<em> </em>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.</p>

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

Masters Thesis

Year dc:date.available

2022

Author dc:creator

• Hugi, April

Contributors dc:contributor

• Dr. Frank Hernandez
• Dr. Chet Rakocinski
• Dr. Simon Geist

• Istiophorid
• Sex-specific prey selection
• oligotrophic
• mesoscale feature
• essential fatty acid

Repository record dc:identifier

https://aquila.usm.edu/masters_theses/891

OAI identifier oai:identifier

oai:aquila.usm.edu:masters_theses-1954