Movements of blue sharks (Prionace glauca) across their life history

PLoS One. 2014 Aug 13;9(8):e103538. doi: 10.1371/journal.pone.0103538. eCollection 2014.

Abstract

Spatial structuring and segregation by sex and size is considered to be an intrinsic attribute of shark populations. These spatial patterns remain poorly understood, particularly for oceanic species such as blue shark (Prionace glauca), despite its importance for the management and conservation of this highly migratory species. This study presents the results of a long-term electronic tagging experiment to investigate the migratory patterns of blue shark, to elucidate how these patterns change across its life history and to assess the existence of a nursery area in the central North Atlantic. Blue sharks belonging to different life stages (n = 34) were tracked for periods up to 952 days during which they moved extensively (up to an estimated 28.139 km), occupying large parts of the oceanic basin. Notwithstanding a large individual variability, there were pronounced differences in movements and space use across the species' life history. The study provides strong evidence for the existence of a discrete central North Atlantic nursery, where juveniles can reside for up to at least 2 years. In contrast with previously described nurseries of coastal and semi-pelagic sharks, this oceanic nursery is comparatively vast and open suggesting that shelter from predators is not its main function. Subsequently, male and female blue sharks spatially segregate. Females engage in seasonal latitudinal migrations until approaching maturity, when they undergo an ontogenic habitat shift towards tropical latitudes. In contrast, juvenile males generally expanded their range southward and apparently displayed a higher degree of behavioural polymorphism. These results provide important insights into the spatial ecology of pelagic sharks, with implications for the sustainable management of this heavily exploited shark, especially in the central North Atlantic where the presence of a nursery and the seasonal overlap and alternation of different life stages coincides with a high fishing mortality.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animal Migration*
  • Animals
  • Female
  • Male
  • Oceans and Seas
  • Seasons
  • Sexual Maturation
  • Sharks / physiology*
  • Time Factors

Grants and funding

This work was conducted in the framework of the EU FP7 project MADE, Mitigating adverse ecological impacts of open ocean fisheries (FP7 KBBE/2007/1/210496). FCT/MCTES-MEC provided individual funding to FV, JF and PA (SFRH/BD/46891/2008, SFRH/BPD/66532/2009, and Ciência 2008/POPH/QREN). IMAR-DOP/UAz is Research and Development Unit no. 531 and LARSyS-Associated Laboratory no. 9 funded by the Portuguese Foundation for Science and Technology (FCT) through FCT - Pest/OE/EEI/LA0009/2011–2014 and by the Azores Fund for Science and Technology (FRCT), funded by OE, COMPETE, QREN and ProConvergencia. The Open Access of this paper is funded by FCT - Pest/OE/EEI/LA0009/2014 (OE, COMPETE and QREN). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.