Comparative feeding ecology of bull sharks (Carcharhinus leucas) in the coastal waters of the southwest Indian Ocean inferred from stable isotope analysis

PLoS One. 2013 Oct 21;8(10):e78229. doi: 10.1371/journal.pone.0078229. eCollection 2013.

Abstract

As apex predators, sharks play an important role shaping their respective marine communities through predation and associated risk effects. Understanding the predatory dynamics of sharks within communities is, therefore, necessary to establish effective ecologically based conservation strategies. We employed non-lethal sampling methods to investigate the feeding ecology of bull sharks (Carcharhinus leucas) using stable isotope analysis within a subtropical marine community in the southwest Indian Ocean. The main objectives of this study were to investigate and compare the predatory role that sub-adult and adult bull sharks play within a top predatory teleost fish community. Bull sharks had significantly broader niche widths compared to top predatory teleost assemblages with a wide and relatively enriched range of δ(13)C values relative to the local marine community. This suggests that bull sharks forage from a more diverse range of δ(13)C sources over a wider geographical range than the predatory teleost community. Adult bull sharks appeared to exhibit a shift towards consistently higher trophic level prey from an expanded foraging range compared to sub-adults, possibly due to increased mobility linked with size. Although predatory teleost fish are also capable of substantial migrations, bull sharks may have the ability to exploit a more diverse range of habitats and appeared to prey on a wider diversity of larger prey. This suggests that bull sharks play an important predatory role within their respective marine communities and adult sharks in particular may shape and link ecological processes of a variety of marine communities over a broad range.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Ecology
  • Ecosystem
  • Feeding Behavior / physiology*
  • Food Chain
  • Indian Ocean
  • Isotopes / administration & dosage*
  • Predatory Behavior / physiology*
  • Sharks / physiology*

Substances

  • Isotopes

Grants and funding

This study would not have been possible without funding and support from the Professional Development Programme of the South African National Research Foundation (NRF), Rhodes University, Port Elizabeth Museum at Bayworld and Bayworld Center for Research and Education who administered the grant, as well as Fathoms Research who contributed to the research funding. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.