Identifying key environmental variables of two seahorse species (Hippocampus guttulatus and Hippocampus hippocampus) in the Ria Formosa lagoon, South Portugal
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.
KeywordsHippocampus 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 (http://seahorse.fisheries.ubc.ca/) for providing logistic support for underwater surveys and to all the volunteers that have participated in the data collection.
Compliance with ethical standards
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.
- Baum JK, Meeuwig JJ, Vincent ACJ (2003) Bycatch of lined seahorses (Hippocampus erectus) in a Gulf of Mexico shrimp trawl fishery. Fish Bull 101:721–731Google Scholar
- Bell EM, Lockyear JF, McPherson JM, Marsden AD, Vincent ACJ (2003) First field studies of an endangered south African seahorse. Hippocampus capensis Environ Biol Fishes 67:35–46Google Scholar
- Correia, M. (2015). Trends in seahorse abundance in the Ria Formosa, South Portugal: recent scenario and future prospects. p. 128 pp. Faro: Universidade do AlgarveGoogle Scholar
- Hastie T, Tibshirani R (1990) Generalized additive models. Chapman and Hall, LondonGoogle Scholar
- IUCN (2014). IUCN Red List of Threatened Species. Version 2014.2. www.iucnredlist.org
- Lourie SA, Foster SJ, Cooper EW, Vincent AC (2004) A guide to the identification of seahorses. Project seahorse and TRAFFIC North America. University of British Columbia and World Wildlife Fund, Washington, DCGoogle Scholar
- Martins, J. T., Ferreira, Ó., Ciavola, P. & Dias, J. A. (1996). Monitoring of profile changes at Praia de Faro, Algarve: a tool to predict and solve problems. In Partnership in Coastal Zone Management. (Taussik, J. & Mitchell, J., eds.), pp. 615–622: Samara Publishing Limited, CardiganGoogle Scholar
- Masonjones HD, Rose E, McRae LB, Dixson DL (2010) An examination of the population dynamics of syngnathid fishes within Tampa Bay, Florida. USA Current Zoology 56:118–133Google Scholar
- R Core Team (2016) R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna. https://www.R-project.org/
- Rosa IL, Oliveira TPR, Castro ALC, de Souza Moraes LE, Xavier JHA, Nottingham MC, Dias TLP, Bruto-Costa LV, Araújo ME, Birolo AB, Mai ACG, Monteiro-Neto C (2007) Population characteristics, space use and habitat associations of the seahorse Hippocampus reidi (Teleostei: Syngnathidae). Neotrop Ichthyol 5(3):405–414CrossRefGoogle Scholar
- Vincent, A. C. J. (1996). The international trade in seahorses. In TRAFFIC International, p. 163. Cambridge, UKGoogle Scholar
- Wood S (2001) mgcv: GAMs and generalized ridge regression for R. R News 1:20–25Google Scholar