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. A total of 16,188 fishes were identified. Previously reported fish species and family richness for the GP region was increased ~32%, to 99 and 37, respectively. Eleven species (Chromis atrilobata, Haemulon maculicauda, H. steindachneri, Abudefduf troschelii, Apogon pacificus, Clupeidae sp., Thalassoma lucasanum, Halichoeres dispilus, Caranx caballus, Stegastes flavilatus, and S. acapulcoensis) accounted for ~ 80% 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, range 0.47 - 0.94), and species richness (S = 19 ± 6.2, range 7 - 32). Results suggested mixed spatio-temporal variability patterns. Euclidian distance between sites was not a factor, but habitat attributes were. The first two axes of a Principal Component Analysis accounted for only 25% of the variation, but suggested an influence of sampling month, Caulerpa sertulariodes algal cover, slope, depth, rugosity, and live coral cover. The onset and increase of C. sertularioides cover at several study sites confirmed concerns about the invasive nature of this macroalga. By having large-range species dominating the fish assemblages, GP ichthyofauna appears to be more resilient to drastic changes in water conditions