New publication: Climate variability influences the abundance of coastal dolphins

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We are pleased to announce the following publication in Global Change Biology entitled:

EL NIÑO SOUTHERN OSCILLATION INFLUENCES THE ABUNDANCE AND MOVEMENTS OF A MARINE TOP PREDATOR IN COASTAL WATERS

Authors: Kate R. Sprogis, Fredrik Christiansen, Moritz Wandres and Lars Bejder.

Citation: KR Sprogis, F Christiansen, M Wandres, and L Bejder (2017) El Niño Southern Oscillation influences the abundance and movements of a marine top predator in coastal waters. Global Change Biology. doi: 10.1111/gcb.13892.

Summary:

  • Off southwest Australia, the Bunbury bottlenose dolphin (Tursiops aduncus population has been studied intensively through the South West Marine Research Program, yielding a robust dataset that captures seasonal variations in both abundance and movement patterns.
  • In Western Australia, the El Niño Southern Oscillation (ENSO) affects the strength of the Leeuwin Current, the dominant oceanographic feature in the region. The strength and variability of the Leeuwin Current affects marine ecosystems and distribution of prey for top predators.

Aim of the study:

  • We examined the effect of ENSO on the abundance and movements of a resident bottlenose dolphin) population off Bunbury (Figure 1).

Fig. 1 Study area off Bunbury, southwest Australia, where dolphin photo-identification surveys were conducted from 2007-2013. Boat-based transects were conducted for abundance estimates in the Inner waters (bay, inlet, estuary and river), Back Beach and Buffalo Beach (zig-zag lines). The southward flowing Leeuwin Current is the main oceanographic feature off Western Australia (designated by the arrow in the insert).

What did we find?

  • Dolphin abundance was significantly affected by ENSO. The magnitude of the effect was dependent upon season. Dolphin abundance was lowest during winter 2009, when dolphins had high movement rates out of the study area. This coincided with an El Niño event (Figure 2).
  • During the El Niño event there was an above-average rainfall and a decrease in sea surface temperature (Figure 3).
  • These conditions may have affected the distribution of dolphin prey, resulting in the movement of dolphins out of the study area in search of adequate prey.

 

Fig. 2 Note the a) El Niño event in 2009, b) peak in rainfall at the beginning of winter 2009, c) peak in temporary emigration from autumn to winter 2009, and d) a decrease in abundance in winter 2009.

Overall importance of research findings:

  • This study demonstrated the local effects of large-scale climatic variations on the short-term response of a resident and coastal delphinid species.
  • With a projected global increase in frequency and intensity of extreme climatic events (e.g. floods, hurricanes), coastal, resident dolphin populations may not only have to contend with increasing coastal anthropogenic activities (e.g. coastal development and shipping), but also have to adapt to large-scale climatic changes.

Fig. 3 Sea surface temperature (SST) anomalies for south-west Australia. Darker red indicates a positive anomaly, with an increase in SST. Darker blue indicates a negative anomaly, with a decrease in SST. Note the negative anomaly for the moderate El Niño around June 2009 (winter).

Download the paper:
To read more the article is available from Global Change Biology, or alternatively, if you are unable to download the article please email K.Sprogis at murdoch.edu.au for a pdf, or request a copy through Research Gate.

South West Marine Research Program publications:

  • Sprogis K.R., Raudino H.C., Hocking D., Bejder L. (2017) Complex prey handling of octopus by bottlenose dolphins (Tursiops aduncus). Marine Mammal Science, 33, 934-945. doi: 10.1111/mms.12405
  • Manlik, O., McDonald, J.A. Mann, J., Raudino, H.C., Bejder, L., Krützen, K., Connor, R.R., Heithaus, M.R., Lacy, R.C. and Sherwin, W.B. (2016).  The relative importance of reproduction and survival for the conservation of two dolphin populations. Ecology and Evolution. doi: 10.1002/ece3.2130
  • Smith, H.C., and Sprogis, K.R. (2016). Seasonal feeding on giant cuttlefish (Sepia apama) by Indo-Pacific bottlenose dolphins (Tursiops aduncus) in south-western Australia. Australian Journal of Zoology. doi: http://dx.doi.org/10.1071/ZO15075
  • McCluskey, S.M., Bejder, L., and Loneragan, N.R. (2016). Assessing potential dolphin prey availability and calorific value in an estuarine and coastal environment. Frontiers in Marine Science 3. doi: 10.3389/fmars.2016.00030
  • Sprogis, K.R., Pollock, K.H., Raudino, H.C., Allen, S.J., Kopps, A.M., Manlik, O., Tyne, J.A., and Bejder, L. (2016). Sex-specific patterns in abundance, temporary emigration and survival of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in coastal and estuarine waters. Frontiers in Marine Science 3. doi: 10.3389/fmars.2016.00012
  • Sprogis, K.R., Raudino, H.C., Rankin, R., MacLeod, C.D., and Bejder, L. (2016). Home range size of adult Indo-Pacific bottlenose dolphins (Tursiops aduncus) in a coastal and estuarine system is habitat and sex-specific. Marine Mammal Science 32, 287-308. doi: 10.1111/mms.12260
  • Smith, H.C., Frère, C., Kobryn, H., and Bejder, L. (2016). Dolphin sociality, distribution and calving as important behavioural patterns informing management. Animal Conservation. doi: 10.1111/acv.12263
  • Smith H.C., Pollock, K., Waples, K., Bradley, S., and Bejder, L. (2013). Use of the robust design to estimate seasonal abundance and demographic parameters of a coastal bottlenose dolphin (Tursiops aduncus) population. PLoS ONE 8, e76574. doi: 10.1371/journal.pone.0076574

Acknowledgements:
We thank our numerous research assistants who assisted with fieldwork and data processing. Thank you to Dr Holly Raudino and to our research associates for collecting field data and/or assistance with data management; M. Cannon, D. Chabanne, V. Buchanan, K. Nicholson and B. Goguelat. Thank you to the Western Australian Department of Parks and Wildlife for providing bottlenose dolphin stranding data from the strandings database. We are grateful to two anonymous reviewers whose comments greatly improved this manuscript.

Project Funding:
We thank the funding partners for financial support from the South West Marine Research Program; Bemax Cable Sands, BHP Billiton Worsley Alumina Ltd, the Bunbury Dolphin Discovery Centre, Bunbury Port Authority, City of Bunbury, Cristal Mining, the Western Australian Department of Parks and Wildlife, Iluka, Millard Marine, Naturaliste Charters, Newmont Boddington Gold, South West Development Commission and WA Plantation Resources.

Permits and Ethics:
All research was approved and permitted through the Department of Parks and Wildlife (SF005811, SF007986, SF008624) and Murdoch University’s Animal Ethics Committee (W2009/06, W2342/10).

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