Masters Student
Jack Dales

Stable Isotope Analysis (SIA) of Juvenile Lemon Sharks, Negaprion brevirostris, within Coastal and Island Nurseries

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Lemon sharks, Negaprion brevirostris, are a large coastal species of shark that have a wide distribution along the eastern coast of the United States, the Caribbean, and South America ranging from New Jersey to Brazil in the Western North Atlantic Ocean (Compagno, 1984). Lemon sharks exhibit site fidelity to nursery areas in Bimini, Bahamas and the southeast United States: coastal Georgia, Cape Canaveral (FL) and the Florida Keys (Barker et al. 2005; Chapman et al., 2009; Kessel et al., 2014; Reyier et al., 2008). Born along the East Coast of the US (Carolinas and Georgia), juveniles will undergo large movements southward, to an overwintering site near Cape Canaveral, FL coinciding with decreasing water temperatures (Reyier et al., 2014). While in Cape Canaveral, juvenile lemon sharks utilize near shore troughs along open beach habitats which is drastically different compared to the estuarine tidal creeks of coastal Georgia where the same individuals are born during the summer months. Inversely, juvenile lemon sharks in Bimini remain in their same primary nursery habitats for 3-5 years before expanding their range within Bimini and eventually dispersing when large enough (Chapman et al., 2009; Franks 2007). Lemon sharks in the Florida Keys (Marquesas Keys) exhibit faster growth rates compared to Bimini and therefore isotopic values may differ although habitat and prey types are similar between sites (Barker et al., 2005). Analyzing multiple tissues with different turnover rates from the same sharks will provide recent and average diet and habitat use across multiple nursery sites.

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Geographically separated nursery sites are subject to differences in temperature regimes, habitat type, and predator and prey availability, influencing the ecology of juvenile lemon sharks within nurseries in the Western North Atlantic. Assessing multiple populations of juvenile lemon sharks through multi-tissue stable isotope analysis will provide both long term and recent diet and habitat use in nursery areas. Determining how juvenile lemon sharks utilize separate nursery habitats will contribute to accurately managing and monitoring populations at vulnerable stages of life histories.

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Main research question:

• Does the diet and trophic position of juvenile lemon sharks change within geographically distinct nursery habitats in the Western North Atlantic?

  • Bimini and the Florida Keys provide similar nursery habitats for juvenile lemon sharks but do they use the habitats the same?

  • Juvenile lemon sharks born in South Carolina and Georgia during the summer months undergo large movements south to Central Florida to overwinter. How does large scale movements at early stages of life affect their isotopic values?

 

Nursery study sites:

• Bimini, Bahamas

• Cape Canaveral, Florida

• Coastal Georgia

• Florida Keys
  
   

Works Cited

Barker, M. J., Gruber, S. H., Newman, S. P., & Schluessel, V. (2005). Spatial and ontogenetic variation in growth of nursery-bound juvenile lemon sharks, Negaprion brevirostris: a comparison of two age-assigning techniques. Environmental Biology of Fishes, 72(3), 343-355.

Chapman, D. D., Babcock, E. A., Gruber, S. H., Dibattista, J. D., Franks, B. R., Kessel, S. A., ... & Feldheim, K. A. (2009). Long‐term natal site‐fidelity by immature lemon sharks (Negaprion brevirostris) at a subtropical island. Molecular ecology, 18(16), 3500-3507.

Compagno, L. J. (1984). FAO species catalogue. v. 4:(2) Sharks of the world. An annotated and illustrated catalogue of shark species known to date, pt. 2: Carcharhiniformes.

Franks, B. R. (2007). The spatial ecology and resource selection of juvenile lemon sharks (Negaprion brevirostris) in their primary nursery areas (Vol. 68, No. 11).

Kessel, S. T., Chapman, D. D., Franks, B. R., Gedamke, T., Gruber, S. H., Newman, J. M., ... & Perkins, R. G. (2014). Predictable temperature-regulated residency, movement and migration in a large, highly mobile marine predator (Negaprion brevirostris). Marine Ecology Progress Series, 514, 175-190.

Reyier, E. A., Adams, D. H., & Lowers, R. H. (2008). FIRST EVIDENCE OF A HIGH DENSITY NURSERY GROUND FOR THE LEMON SHARK, NEGAPRION BREVIROSTRIS, NEAR CAPE CANAVERAL, FLORIDA. Florida Scientist, 71(2), 134–148.

Reyier, E. A., Franks, B. R., Chapman, D. D., Scheidt, D. M., Stolen, E. D., & Gruber, S. H. (2014). Regional-scale migrations and habitat use of juvenile lemon sharks (Negaprion brevirostris) in the US South Atlantic. PLoS One, 9(2), e88470.