Bioecology and movements of bull sharks, Carcharhinus leucas , caught in a long-term longline survey off northeastern Brazil

Yuri V Niella,André S Afonso,Fábio H V Hazin

doi:10.1590/1982-0224-20170106

Yuri V Niella, André S Afonso + Show 1 more

Open Access

https://doi.org/10.1590/1982-0224-20170106

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Abstract

ABSTRACT A robust understanding of habitat usage by coastal shark species, and how it overlaps with human presence in densely-populated regions is needed to inform the development of efficient conservation strategies for these important top predators. An intensive longline survey conducted in nearshore waters off northeastern Brazil from 2004 through 2014 caught a total of 18 bull sharks (Carcharhinus leucas) (male-female ratio = 0.63:1), which can be dangerous to humans. Although most sharks were sexually mature, there was no evidence that this region could be used as a parturition or nursery area. Prey items identified in the guts of the sharks comprised teleosts, mollusks and elasmobranchs. Additionally, one satellite-tagged bull shark covered a great distance (> 3,000 km) in 75 days at liberty, making most use of shallow waters (< 20 m depth) and presumably also entering an estuarine area. Although bull sharks are not an important fishery resource in this region, such a reduced abundance coupled with its affinity for coastal and inshore habitats highlights the potential vulnerability of C. leucas to deleterious anthropic interferences off northeastern Brazil.

Highlights

Increasing human populations have generally been responsible for negative influences such as overfishing, water pollution and climate change on coastal ecosystems (Jackson et al, 2001), which correspond to important foraging and nursery grounds for several shark species (Heithaus et al, 2002; Simpfendorfer et al, 2005; Wiley, Simpfendorfer, 2007)
This study aims at assessing the population structure of C. leucas off Recife and providing preliminary information on the bioecological traits of this species in a region poorly known to marine sciences, benefiting its conservation
Mature C. leucas were more represented in the catch (61.1%) and were mostly caught during the austral summer (81.8%), when a higher abundance of bull sharks has been reported in this region (Afonso et al, 2017)

Summary

Introduction

Increasing human populations have generally been responsible for negative influences such as overfishing, water pollution and climate change on coastal ecosystems (Jackson et al, 2001), which correspond to important foraging and nursery grounds for several shark species (Heithaus et al, 2002; Simpfendorfer et al, 2005; Wiley, Simpfendorfer, 2007). The bull shark, Carcharhinus leucas (Müller & Henle, 1839), is a large carcharhinid, which can grow up to 4 m in total length (LT) (McCord, Lamberth, 2009). It is circumglobal in tropical and warm temperate coastal waters (Compagno, 2001; Hueter et al, 2005) and in e170106[1]

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