Environmental Biology of Fishes

, Volume 101, Issue 9, pp 1357–1367 | Cite as

Identifying key environmental variables of two seahorse species (Hippocampus guttulatus and Hippocampus hippocampus) in the Ria Formosa lagoon, South Portugal

  • Miguel CorreiaEmail author
  • Heather Jane Koldewey
  • José Pedro Andrade
  • Eduardo Esteves
  • Jorge Palma


Recent findings reported a significant decrease in abundance of two seahorse species (Hippocampus guttulatus and H. hippocampus) in the Ria Formosa lagoon (South Portugal) and no direct causes have been, so far, clearly identified. This study aimed to describe fluctuations in the local seahorse populations through monthly surveys over a course of a year, in order to identify some of the potential drivers behind the seasonal fluctuations. A total of six sites were chosen based on their habitat characteristics. The highest H. guttulatus abundances were recorded at sites with higher holdfast availability and depth ranging from 3 to 6 m, while H. hippocampus were observed at highest numbers in sites with lower holdfast availability and patchy distribution. In most sites, seahorse density decreased during the summer months (from May to August) and increased from August to December. Holdfast use changed across the surveyed sites, according to the respective habitat characteristics. This study identified environmental variables that influenced the abundance of seahorse population, i.e., holdfast availability, depth and temperature in the Ria Formosa lagoon, underlining the importance of monitoring populations over a course of no less than a year in order to avoid bias due to seasonal fluctuations. Identifying critical habitats will provide valuable information for local authorities in order to implement protective measures towards seahorse conservation.


Hippocampus guttulatus Hippocampus hippocampus Syngnathidae Long term survey Population abundance Seasonal changes 



Miguel Correia was supported by a PhD grant (Fundação para a Ciência e Tecnologia - Portugal) (BD/41020/2007). The study was supported by the scientific projects INAQUA (Oceanario de Lisboa, National Geographic Channel) and HIPPOSAFE (Fundação para a Ciência e Tecnologia, ref. PTDC/MAR/122616/2010). Thanks are also due to Project Seahorse ( for providing logistic support for underwater surveys and to all the volunteers that have participated in the data collection.

Compliance with ethical standards

Ethical compliance

All applicable international, national, and/or institutional guidelines for the care and use of animals were followed.

Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© Springer Nature B.V. 2018

Authors and Affiliations

  1. 1.CCMAR, Centro de Ciências do MarUniversidade do AlgarveFaroPortugal
  2. 2.Project Seahorse, Zoological Society of LondonLondonUK
  3. 3.Departamento de Engenharia Alimentar, Instituto Superior de EngenhariaUniversidade do AlgarveFaroPortugal

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