USF St. Petersburg campus Faculty Publications


Stable isotopes in the eye lenses of Doryteuthis plei (Blainville 1823): Exploring natal origins and migratory patterns in the eastern Gulf of Mexico

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Heather L. Judkins

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Eye lenses of Doryteuthis plei (Blainville 1823), the slender inshore squid or arrow squid, were used to re-create lifetime δ13C and δ15N histories for 42 individuals (21 males, 21 females) collected by trawl from the West Florida Shelf (WFS). These histories were compared against isoscapes for the Gulf of Mexico to infer geographic movements over the squid's life. Most individuals (62%) had significant lifetime increases in δ13C, indicating landward movement, while only 12% of individuals indicated seaward movement. Males appeared to have a reduced tendency to move landward (38 vs 86% in females). Lifetime increases in δ15N indicated males and females had similar tendencies toward northward movement (71 vs 62%). The above patterns were interpreted as being geographic because the slopes of coupled changes in δ15N and δ13C were largely inconsistent with numeric expectations of increasing trophic level during life. Lifetime habitat shifts appeared to be continuous rather than saltatory (stepped). When plotted together, δ13C and δ15N did not occur in discrete clusters and often varied together in a linear manner. Isotopes from the central core of the lens, which represents the earliest period of post-embryonic life, were variable, with no apparent clustering when plotted, suggesting widely dispersed spawning grounds. Core isotope values were consistent with spawning on the outer WFS, possibly in association with the deep chlorophyll maximum. © 2019 Elsevier Ltd