Body condition predicts energy stores in apex predatory sharks.
Animal condition typically reflects the accumulation of energy stores (e.g. fatty acids), which can influence an individual's decision to undertake challenging life-history events, such as migration and reproduction. Accordingly, researchers often use measures of animal body size and/or weight as an index of condition. However, values of condition, such as fatty acid levels, may not always reflect the physiological state of animals accurately. While the relationships between condition indices and energy stores have been explored in some species (e.g. birds), they have yet to be examined in top predatory fishes, which often undertake extensive and energetically expensive migrations. We used an apex predatory shark (Galeocerdo cuvier, the tiger shark) as a model species to evaluate the relationship between triglycerides (energy metabolite) and a metric of overall body condition. We captured, blood sampled, measured and released 28 sharks (size range 125-303 cm pre-caudal length). In the laboratory, we assayed each plasma sample for triglyceride values. We detected a positive and significant relationship between condition and triglyceride values (P < 0.02). This result may have conservation implications if the largest and highest-condition sharks are exploited in fisheries, because these individuals are likely to have the highest potential for successful reproduction. Our results suggest that researchers may use either plasma triglyceride values or an appropriate measure of body condition for assessing health in large sharks.
Leonard and Jayne Abess Center for Ecosystem Science and Policy, University of Miami, PO Box 248203, Coral Gables, FL 33124, USA; R.J. Dunlap Marine Conservation Program, 4600 Rickenbacker Causeway, Miami, FL 33149, USA; Beneath the Waves Incorporated, 110 W. Fayette Street, Suite 900, Syracuse, NY 13202, USA.
Austin J
AJ
Gallagher
Rosenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Causeway, Miami, FL 33149, USA.
Dominique N
DN
Wagner
Department of Biology, University of Massachusetts at Amherst, 221 Morrill Science Center, Amherst, MA 01003, USA; Organismic and Evolutionary Biology Program, University of Massachusetts Amherst, Amherst, MA 01003, USA.
Duncan J
DJ
Irschick
Leonard and Jayne Abess Center for Ecosystem Science and Policy, University of Miami, PO Box 248203, Coral Gables, FL 33124, USA; R.J. Dunlap Marine Conservation Program, 4600 Rickenbacker Causeway, Miami, FL 33149, USA; Rosenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Causeway, Miami, FL 33149, USA.
Neil
N
Hammerschlag
Condition; energy; movement; natural selection; shark; trade-offs