ESR 32:491-506 (2017)  -  DOI: https://doi.org/10.3354/esr00824

Sympatric elasmobranchs and fecal samples provide insight into the trophic ecology of the smalltooth sawfish

Gregg R. Poulakis1,*, Hidetoshi Urakawa2, Philip W. Stevens3, Jacquelyn A. DeAngelo1, Amy A. Timmers1, R. Dean Grubbs4, Aaron T. Fisk5, Jill A. Olin6

1Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission, Charlotte Harbor Field Laboratory, Port Charlotte, Florida 33954, USA
2Department of Marine and Ecological Sciences, Florida Gulf Coast University, Fort Myers, Florida 33965, USA
3Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission, St. Petersburg, Florida 33701, USA
4Florida State University Coastal and Marine Laboratory, St. Teresa, Florida 32358, USA
5Great Lakes Institute for Environmental Research, University of Windsor, Windsor, Ontario N9B 3P4, Canada
6School of Marine and Atmospheric Science, Stony Brook University, Stony Brook, New York 11794, USA
*Corresponding author:

ABSTRACT: Growing concerns about the conservation of elasmobranchs have prompted a surge in research, because scientific studies that can support management actions are needed. Sawfishes are among the most threatened fishes worldwide and epitomize the challenge of conserving widely distributed, large-bodied marine fishes. We used a comparative approach to provide data on the trophic ecology of the smalltooth sawfish Pristis pectinata in the western Atlantic coastal waters of southwest Florida, USA. Specifically, we applied (1) stable isotope techniques to fin tissues of smalltooth sawfish and 2 sympatric elasmobranch species that have well-documented diets (i.e. bull shark Carcharhinus leucas and cownose ray Rhinoptera bonasus), and muscle tissue from a variety of known and potential prey species; and (2) an 18S rRNA gene sequencing technique to identify prey taxa in sawfish fecal samples. These analyses provided evidence that the smalltooth sawfish feeds primarily on teleost and elasmobranch fishes at all life stages even though sawfish move from estuarine to coastal habitats during their ontogeny. Although both sawfish and bull sharks occupy estuarine waters as juveniles and are piscivorous, the results also indicate that these species partition habitat. The cownose ray has been thought of as migratory throughout its range, but these data indicate that non-migratory, estuarine populations exist at lower latitudes. Collectively, these results will aid in the development of management decisions regarding these species and in improving long-term recovery planning for the smalltooth sawfish.


KEY WORDS: Pristis pectinata · Carcharhinus leucas · Rhinoptera bonasus · Stable isotopes · High-throughput sequencing · Habitat partitioning · Management · Ontogenetic habitat shifts


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Cite this article as: Poulakis GR, Urakawa H, Stevens PW, DeAngelo JA and others (2017) Sympatric elasmobranchs and fecal samples provide insight into the trophic ecology of the smalltooth sawfish. Endang Species Res 32:491-506. https://doi.org/10.3354/esr00824

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