Marine aquaculture and bottlenose dolphins’ (Tursiops truncatus) social structure

  • Bruno Díaz López
  • Julia Andrea Bernal Shirai
Original Paper

Abstract

In this study, we investigate association patterns of 249 bottlenose dolphin feeding groups off Sardinia Island (Italy) from January 2000–May 2007 and describe how their association behaviour is related to their response to food patches created by a marine fin fish farm. We also tested the hypothesis that dolphins have different social structures with different feeding activities: Associations should decrease during opportunistic feeding behaviours as it is easier to capture prey, and cooperation is not as necessary. Sixteen individually identified bottlenose dolphins were observed participating in both opportunistic and not opportunistic feeding activities, with a mean of 30 ± 8 times and 9.6 ± 1 times, respectively. Bottlenose dolphins show non-random social behaviour during feeding and this behaviour differs depending on their specific foraging activity. Dolphin associations during feeding can be divided into three categories: acquaintances, affiliates, and feeding associates. Association behaviour during fish farm feeding is consistent with our hypothesis that during opportunistic behaviours, benefits from cooperation decrease, as it is easier to capture prey. Group size homogeneity in both feeding activities demonstrates that the number of dolphins engaging in foraging is not necessarily related with cooperation levels. Moreover, an adult dolphin may prefer to associate with a specific individual, independent of the sex, who shares the same foraging priorities. This study is the first to show how aquaculture is not only directly affecting marine predators but could also indirectly affect their social structure and behaviour.

Keywords

Social structure Fission-fusion societies Aquaculture Bottlenose dolphins Tursiops truncatus 

Notes

Acknowledgement

Funding for this research came from the Bottlenose Dolphin Research Institute—BDRI—and private donations. We give thanks to numerous friends, colleagues and volunteers at the Bottlenose Dolphin Research Institute for their assistance and support with data collection. The English grammar was improved by Collette Thogerson. We would also like to thank Jens Krause and one anonymous referee who provided valuable comments and critiques at various stages of this study. Data collection complies with the current laws of the country in which it was performed.

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Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • Bruno Díaz López
    • 1
  • Julia Andrea Bernal Shirai
    • 1
  1. 1.The Bottlenose Dolphin Research Institute BDRIGolfo AranciItaly

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