Fatty acids and stable isotopes as indicators of early-life feeding and potential maternal resource dependency in the bull shark Carcharhinus leucas

Authors

Laura L. Belicka, Southeast Environmental Research Center, Department of Chemistry and Biochemistry and Marine Sciences Program, Florida International UniversityFollow
Philip Matich, Department of Biological Sciences and Marine Sciences Program, Florida International UniversityFollow
Rudolf Jaffe, Southeast Environmental Research Center, Department of Chemistry and Biochemistry and Marine Sciences Program, Florida International UniversityFollow
Michael R. Heithaus, Department of Biological Sciences and Marine Sciences Program, Florida International UniversityFollow

Abstract

The degree of reliance of newborn sharks on energy reserves from maternal resource allocation and the timescales over which these animals develop foraging skills are critical factors towards understanding the ecological role of top predators in marine ecosystems. We used muscle tissue stable carbon isotopic composition and fatty acid analysis of bull sharks Carcharhinus leucas to investigate early-life feeding ecology in conjunction with maternal resource dependency. Values of δ¹³C of some young-of-the-year sharks were highly enriched, reflecting inputs from the marine-based diet and foraging locations of their mothers. This group of sharks also contained high levels of the 20:3ω9 fatty acid, which accumulates during periods of essential fatty acid deficiency, suggesting inadequate or undeveloped foraging skills and possible reliance on maternal provisioning. A loss of maternal signal in δ¹³C values occurred at a length of approximately 100 cm, with muscle tissue δ¹³C values reflecting a transition from more freshwater/estuarine-based diets to marine-based diets with increasing length. Similarly, fatty acids from sharks >100 cm indicated no signs of essential fatty acid deficiency, implying adequate foraging. By combining stable carbon isotopes and fatty acids, our results provided important constraints on the timing of the loss of maternal isotopic signal and the development of foraging skills in relation to shark size and imply that molecular markers such as fatty acids are useful for the determination of maternal resource dependency.

Comments

This material is based upon work supported by the National Science Foundation through the Florida Coastal Everglades Long-Term Ecological Research program under Cooperative Agreements #DBI-0620409 and #DEB-9910514. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

Recommended Citation

Belicka, L., P. Matich, R. Jaffe, M.R. Heithaus. 2012 (In Press). Fatty acids and stable isotopes as indicators of early-life feeding and maternal resource dependency in the bull shark Carcharhinus leucas. Marine Ecology Progress Series DOI: 10.3354/meps09674