title: Seahorse (Hippocampinae) population fluctuations in the Ria Formosa Lagoon, south Portugal.
abstract: Comparisons of three sets of surveys in the Ria Formosa Lagoon, Portugal, over a 13 year period (2001-2002, 2008-2009 and 2010-2013) revealed significant population fluctuations in at least one of the two seahorse (Hippocampinae) species living there, and that those fluctuations were potentially associated with habitat changes in the lagoon. After a significant decline between the first two survey periods (2001-2002 v. 2008-2009), long-snouted seahorse Hippocampus guttulatus populations increased significantly between 2008-2009 surveys and new 2010-2013 surveys. There were no significant differences in H. guttulatus populations between the 2001-2002 and 2010-2013 surveys. In contrast, there were no significant differences in short-snouted seahorse Hippocampus hippocampus densities among the 16 sites surveyed throughout the three sampling periods, although the ability to detect any change was hampered by the low densities of this species in all time periods. Fluctuations in H. guttulatus densities were positively correlated with the percentage of holdfast coverage, but with none of the other environmental variables tested. These results highlight the importance of holdfast availability in maintaining stable seahorse populations. While population fluctuations are certainly more promising than a consistent downward decline, such extreme fluctuations observed for seahorses in the Ria Formosa Lagoon could still leave these two species vulnerable to any additional stressors, particularly during low density periods.
authors.affiliation: CCMar, Universidade do Algarve, F. C. T., Edificio 7, Campus de Gambelas, Faro 8005-139, Portugal.
authors.forename: M
authors.initials: M
authors.lastname: Correia
authors.affiliation: Hawaii Institute of Marine Biology, School of Ocean and Earth Science and Technology University of Hawaii at Manoa, P. O. Box 1346, Kaneohe, HI 96744, U.S.A.
authors.forename: I R
authors.initials: IR
authors.lastname: Caldwell
authors.affiliation: Project Seahorse, Zoological Society of London, Regent's Park, London NW1 4RY, U.K.
authors.forename: H J
authors.initials: HJ
authors.lastname: Koldewey
authors.affiliation: CCMar, Universidade do Algarve, F. C. T., Edificio 7, Campus de Gambelas, Faro 8005-139, Portugal.
authors.forename: J P
authors.initials: JP
authors.lastname: Andrade
authors.affiliation: CCMar, Universidade do Algarve, F. C. T., Edificio 7, Campus de Gambelas, Faro 8005-139, Portugal.
authors.forename: J
authors.initials: J
authors.lastname: Palma
mesh_terms: D000818:Animals; D017753:Ecosystem; D063366:Estuaries; D016014:Linear Models; D011156:Population Density; D011157:Population Dynamics; D011174:Portugal; D023701:Smegmamorpha
keywords: Hippocampinae; Hippocampus guttulatus; Hippocampus hippocampus; habitat changes; long-term survey