Abstract

Golfo de Papagayo (GP), located on the North Pacific coast of Costa Rica, displays a seasonal coastal upwelling during dry months. Between May 2005 and February 2006, 66 visual censuses were conducted at seven rocky reefs, depths ranging 1.0 - 15 m (6 GP sites and another onshore in Playa Conchal, ~30 Km south). A total of 16,188 fishes were identified. Previously reported fish species and families for the GP region were increased 32%, to 99 and 37, respectively. Five species (Chromis atrilobata, Haemulon maculicada, H. steindachneri, Abudefduf troschelii, and Apogon pacifici) accounted for >56% of the fish. Each site had a particular assemblage, as indicated by site-month interactions found in diversity (H’=2.32 ± 0.37 SD, range 1.36-2.95), evenness (E = 0.81 ± 0.08, 0.47 - 0.94), and species richness (S = 19 ± 6.2, 7 - 32). No significant differences were found, except that a pinnacle reef was the richest during upwelling months, while an inner bay site consistently showed the lowest number of species. Distance between sites was not a factor, but habitat characteristics were. Although the first two axes of a Principal Component Analysis accounted for only 25% of the variation, results suggested an influence of month, Caulerpa sertulariodes algal cover, and slope, followed by depth, rugosity, and live coral cover. Outer sites were visited more by pelagic species during upwelling months, while the two onshore rocky sites assemblages were very similar despite being 30 km apart. The onset and increase of C. sertularioides cover at several study sites confirmed concerns about the invasive nature of this macroalga.

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