Feeding ecology of three coastal shark species in the northwest Gulf of Mexico

Published online on 25. May 2016

Feeding ecology of three coastal shark species in the northwest
Gulf of Mexico

Jeffrey D. Plumlee, R. J. David Wells

ABSTRACT:

The feeding ecology of 3 coastal shark species—Atlantic sharpnose Rhizoprionodon terraenovae, bonnethead Sphyrna tiburo, and blacktip Carcharhinus limbatus shark—was examined in the northwest Gulf of Mexico (GOM). A total of 601 sharks (305 Atlantic sharpnose, 239 bonnethead, and 57 blacktip) were collected over 2 yr from recreational anglers in Galveston, TX. All individuals had stomach contents examined and a subset (50 Atlantic sharpnose, 50 bonnethead, and 36 blacktip sharks) was analyzed for stable isotopes (carbon, nitrogen, and sulfur) in muscle tissue, revealing short-term and long-term feeding strategies. Both blacktip and Atlantic sharpnose shark stomach contents consisted of teleost fishes with percent index of relative importance (%IRI) of 98.95 and 91.16, respectively, whereas bonnethead diets were dominated by crustaceans (%IRI = 87.20). Stable isotope analysis revealed bonnetheads had higher mean carbon (δ¹³C) and lower sulfur (δ³⁴S) values, indicating inshore feeding and a preference for benthic invertebrates, respectively. Atlantic sharpnose and blacktip sharks were shown to feed on similar prey using stomach content analysis, yet Atlantic sharpnose sharks had a broader diet, including cephalopods and crustaceans in addition to teleost fishes. Differences were further established using nitrogen (δ¹⁵N) values, which were significantly lower for Atlantic sharpnose than blacktip sharks. Collectively, stomach contents and stable isotope analyses supported different feeding strategies of 3 common shark species. δ³⁴S appeared to serve as a natural tracer, distinguishing benthic versus pelagic feeding patterns in elasmobranchs. This study provides important ecosystem-based feeding information of upper trophic-level predators in coastal waters of the northwestern GOM.

Mar Ecol Prog Ser 550:163-174

SOURCE ( OPEN ACCESS )