Abstract
Gorgona Island, the major insular area in the Colombian Pacific Ocean, is characterized by a remarkably high biological and ecosystem diversity for this area of the world. Coral reefs are well developed and their fish communities have been described using conventional visual surveys. These methods, however, are known to be biased towards detecting larger and more mobile species, tending to ignore small and cryptobenthic species. The two main objectives of this study were to describe the assemblage structure of the cryptobenthic fish fauna and estimate the extent to which this fauna is underestimated by visual surveys.At the beginning and the end of the warm season, we compared the cryptobenthic fish assemblage recorded using visual surveys against the one recorded using “enclosed anesthetic/rotenone samples” on isolated coral colonies (N=54 beginning of warm season; N=17 end of warm season). The crypthobenthic fish fauna associated to coral colonies was characterized by small body sizes and was composed mainly by species of the families Antennaridae, Blennidae, Gobiidae, Labrisomidae, Muraenidae, Serranidae, Scorpaenidae and Syngnathidae. Conventional visual surveys underestimated overall species richness by 28-36% and number of individuals by 16-35%. Noteworthy, four species recorded during this study using “enclosed anesthetic/rotenone samples” were new records for Gorgona Island. Although both sampling methods can detect a largely overlapping group of species, the “enclosed anesthetic/rotenone samples” method was able to detect more individuals and species, including several species that visual surveys fail to detect. Although this study is the first effort to describe the cryptobenthic fish assemblage associated to coral reefs in the Tropical Eastern Pacific, our results suggest that these assemblages are an important component of the reef fish community in the region in terms of biodiversity and functional roles. Rev. Biol. Trop. 62 (Suppl. 1): 359-371. Epub 2014 February 01.
Highlights
Non-destructive sampling techniques, such as visual surveys, have been widely used in studies of coral reef fish ecology ever since their introduction by Brock (1954)
A comparison between traditional visual surveys against the “enclosed anesthetic/rotenone samples” method allowed us, besides studying the structure of the cryptobenthic fish assemblages, to estimate the extent to which visual surveys underestimate this component of the reef fish community
Temporal patterns of sea surface temperature at Gorgona Island are characterized by a cold and high salinity season between January and April (Giraldo, Rodríguez-Rubio & Zapata, 2008), followed by an increase in temperature and decrease in salinity in April, followed by a gradual reversal in temperature and salinity conditions until December (Zapata, 2001; Giraldo et al, 2008). These temporal climatic patterns have been shown to have an effect on the coral reef fish community (Zapata & Morales, 1997) due to an increase in recruitment during warmer periods as it has been the case in other regions (Sale & Dybdahl, 1975; Talbot, Russel & Anderson, 1978; Bohnsack & Talbot, 1980; Sale & Douglas, 1984; Coles & Tarr, 1990)
Summary
Non-destructive sampling techniques, such as visual surveys, have been widely used in studies of coral reef fish ecology ever since their introduction by Brock (1954). In comparison with the Caribbean and the Indo-Pacific regions, the number of studies describing reef fish communities in the Tropical Eastern Pacific (TEP) is relatively scarce (e.g., Pérez-España, Galván-Magaña & AbitiaCárdenas, 1996; Zapata & Morales, 1997; Aburto-Oropeza & Balart, 2001; Espinoza & Salas, 2005; Alvarez-Filip, Reyes-Bonilla & Calderon-Aguilera, 2006; Dominici-Arosemena & Wolff, 2006; Benfield, Baxter, Guzman & Mair, 2008; Galván-Villa, Arreola-Robles, Ríos-Jara & Rodriguez-Zaragoza, 2010) All of these studies have been based on visual surveys, which are known to lead to an underestimation of community richness and population densities (Brock, 1982, Bellwood & Alcala, 1988). Our study contributes to gain more complete understanding of reef fish community structure in the region
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