February 1st to 5th 2016
Olhão, Portugal
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Artificial Holdfast Units: Accessing Their Usefulness for the Recovery and Conservation of Seahorse Populations in the Ria Formosa lagoon, South Portugal

Oral Presentation
Habitat Loss and Ocean Noise
Friday, February 5, 2016 -
11:45 to 12:00

Correia, M. 1 Andrade, J.P. 2 Palma, J. 3

1Centre of Marine Sciences (CCMAR), University of Algarve, Campus de Gambelas, 8005-139 Faro, Portugal
2Centre of Marine Sciences (CCMAR), University of Algarve, Campus de Gambelas, 8005-139 Faro, Portugal
3Centre of Marine Sciences (CCMAR), University of Algarve, Campus de Gambelas, 8005-139 Faro, Portugal

A significant decline in the seahorse populations in the Ria Formosa (south Portugal) was recently reported and holdfast availability suggested as a particularly important variable that influences the abundance of the long-snouted seahorse Hippocampus guttulatus and the short-snouted seahorse H. hippocampus. In order to test the usefulness of artificial holdfast units (AHU) for the recovery of seahorse habitats, four different artificial holdfasts (S1-S4) were initially tested in laboratory for seahorse preference under different conditions and different holdfast densities. Seahorses, both juveniles and adults, preferred the holdfast S4, consisting of a “Codium-like” polyethylene nautical rope, even when submitted to different water flows. Preferred holdfast density was 156 holdfast.m-2, and most of seahorses were observed grasping at the base of these structures (0-10cm in height). Later on, based on the information collected in the first experiment, several of these structures were built and deployed in the lagoon at four locations with distinct environmental characteristics and surveyed for seahorse abundance during a 6 months period. All AHUs were colonized by seahorses within a month after deployment, reaching a maximum density of 13.1 seahorse m-2 at one of the sites. Results suggest that these AHUs have the potential to aggregate seahorses in damaged habitats and promote their recovery, improving local habitats and overall biodiversity. The results also provide useful guidance for the use of artificial structures to improve degraded seahorse habitats in other similar situations, as part of management plans (including the creation of marine protected areas (MPAs)) for seahorse population recovery and conservation.
keywords: 
seahorse, artificial holdfast, habitat enrichment, marine protected areas

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