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Smooth hammerhead sharks (Sphyrna zygaena) observed off the Portuguese southern coast

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Abstract

Despite its worldwide distribution and vulnerable status, knowledge on the biology and ecology of the smooth hammerhead Sphyrna zygaena in the temperate NE Atlantic is very scarce. Here, we reveal intra-annual fluctuations in S. zygaena abundance in the Portuguese southwestern coast, using sightings data collected on board whale watching boats over five years (2010–14; excluding winter months). Moreover, we investigated how shark abundance is related to local environmental conditions. We describe the first smooth hammerhead “hotspot” in the NE Atlantic, and we show a recurrent pattern of occurrence during the warmer summer and autumn months (from July to October) near Sagres and Martinhal Bay and islands. Intra-annual variations in abundance were significantly associated with sea surface temperature and negatively related with upwelling index and chlorophyll a, suggesting horizontal movements linked to the seasonal changes. Hence, hammerheads moved inshore during the warmer periods (with low primary productivity), due to either direct influence of temperature in their movements or indirect influence in prey distribution. This hammerhead “hotspot” may constitute a nursery ground for S. zygaena, nevertheless, our data does not allow us to prove or refute such claim. Future telemetry-based studies should be conducted to fully understand hammerhead movements and habitat preferences, and to evaluate this “hotspot” as a critical habitat for this predator.

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Notes

  1. http://oceancolor.gsfc.nasa.gov/.

  2. www.indicedeafloramiento.ieo.es.

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Acknowledgments

The authors would like to thank CAPE CRUISER Company (located in Sagres) for the data collection. The Portuguese Foundation for Science and Technology (FCT) supported this study through Programa Investigador FCT 2013 – Development Grant to R. Rosa and the strategic project UID/MAR/04292/2013 granted to MARE.

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Authors and Affiliations

  1. MARE – Marine and Environmental Sciences Centre, Laboratório Marítimo da Guia, Universidade de Lisboa, 2750-374, Cascais, Portugal

    Ana Couto, Eduardo Sampaio, Miguel Furtado, Joana Castro & Rui Rosa

  2. CIBIO/InBIO, Universidade do Porto, Campus Agrário de Vairão, 4485-661, Vairão, Portugal

    Ana Couto & Nuno Queiroz

  3. Centro de Investigaciones Biológicas del Noroeste (CIBNOR), La Paz, Baja California Sur, Mexico

    James T. Ketchum

  4. Pelagios Kakunjá A.C., La Paz, Baja California Sur, Mexico

    James T. Ketchum

  5. Associação para a Investigação do Meio Marinho, 1500-399, Lisbon, Portugal

    André A. Cid & Joana Castro

Authors
  1. Ana Couto
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  2. Nuno Queiroz
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  3. James T. Ketchum
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  4. Eduardo Sampaio
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  8. Rui Rosa
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Correspondence to Ana Couto.

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Couto, A., Queiroz, N., Ketchum, J.T. et al. Smooth hammerhead sharks (Sphyrna zygaena) observed off the Portuguese southern coast. Environ Biol Fish 101, 1261–1268 (2018). https://doi.org/10.1007/s10641-018-0773-8

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  • DOI: https://doi.org/10.1007/s10641-018-0773-8

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