A comparison of visual and collection-based methods for assessing community structure of coral reef fishes in the Tropical Eastern Pacific

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.Key words: cryptobenthic fishes, coral reefs, sampling methods, visual surveys, enclosed anesthetic/rotenone samples.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). However, these techniques have several sources of error due to fish mobility, observer experience and transect size (Thompson & Mapstone, 1997;Ackerman & Bellwood, 2000;Palacios & Zapata, 2011). This leads to a sampling bias toward larger and more mobile species, tending to underestimate small and cryptobenthic fishes. Although it has been suggested that consistent errors and biases in the visual estimates might be acceptable in comparative studies (Brock, 1982;Ackerman & Bellwood, 2000;Willis, 2001), underestimating the cryptobenthic component of reef fish communities might have a potentially larger impact on the understanding of their community assembly, trophic ecology and ultimately on their conservation (Mora, Titterson & Myers, 2008). As a ...

The hidden half: ecology and evolution of cryptobenthic fishes on coral reefs

“…In this context, the diversity, small size, and crypsis of CRFs have historically represented a great challenge. While many large coral reef fishes are adequately surveyed by the most common fish census technique, underwater visual censuses (UVCs; Edgar, Barrett & Morton, ), there is clear evidence that UVCs do not produce reliable estimates of CRF assemblages (Ackerman & Bellwood, ; Smith‐Vaniz et al , ; Alzate, Zapata & Giraldo, ). Indeed, only collection‐based methods provide an adequate representation of CRF communities.…”

“…4A). Specifically, although some data exist from the Eastern Pacific (González-Cabello & Bellwood, 2009;Alzate et al, 2014;Galland et al, 2017), Indo-Australian Archipelago (IAA; e.g. Depczynski & Bellwood, 2005;Ahmadia et al, 2012b), Western Atlantic (e.g.…”

Patterns in Bathyal Demersal Biodiversity and Community Composition Around Archipelagos in the Tropical Eastern Pacific

“…Previous research has assessed marine biodiversity at these islands, but has focused largely on the shallow-water ecosystems (Allen and Robertson, 1994;Glynn et al, 1996;Jost and Andréfouët, 2006;Alzate et al, 2014;Fourriére et al, 2014). Overall, the TEP is noted for its high level of endemism (72%) and relatively diverse shore-fish assemblages (Zapata and Ross Robertson, 2007).…”

A simple spatially explicit neutral model explains the range size distribution of reef fishes

“…Secondly, species range dynamics are affected by numerous ecological and evolutionary factors including biological interactions and the species’ behavioural and functional traits (Stahl, Reu, & Wirth, ). Thirdly, sampling intensity and detection probability vary across space and across species (Alzate, Zapata, & Giraldo, ; Dennis, Sparks, & Hardy, ), and such sampling biases may also drive variation in the apparent range size. Finally, stochastic events, especially during the early life of a species, may bring additional noise to the present‐day range size, making it difficult to find general patterns.…”