Community structure of reef fishes on a remote oceanic island (St Peter and St Paul’s Archipelago, equatorial Atlantic): the relative influence of abiotic and biotic variables

Abstract

This study investigates the reef fish community structure of the world’s smallest remote tropical island, the St Peter and St Paul’s Archipelago, in the equatorial Atlantic. The interplay between isolation, high endemism and low species richness makes the St Peter and St Paul’s Archipelago ecologically simpler than larger and highly connected shelf reef systems, making it an important natural laboratory for ecology and biogeography, particularly with respect to the effects of abiotic and biotic factors, and the functional organisation of such a depauperate community. Boosted regression trees were used to associate density, biomass and diversity of reef fishes with six abiotic and biotic variables, considering the community both as a whole and segregated into seven trophic groups. Depth was the most important explanatory variable across all models, although the direction of its effect varied with the type of response variable. Fish density peaked at intermediate depths, whereas biomass and biodiversity were respectively positively and negatively correlated with depth. Topographic complexity and wave exposure were less important in explaining variance within the fish community than depth. No effects of the predictor biotic variables were detected. Finally, we notice that most functional groups are represented by very few species, highlighting potential vulnerability to disturbances.

Spatial patterns and drivers of fish and benthic reef communities at São Tomé Island, Tropical Eastern Atlantic

“…We found results that are opposite to many studies (e.g., Brokovich et al, ; Tuya et al, ): species richness, abundance and biomass all increased with depth in the range investigated (Figure ). This is similar to what was observed for the very isolated and impoverished St. Peter and St. Paul's Archipelago, in the Mid‐Atlantic (Luiz et al, ). One possible explanation for this pattern would be that deeper areas suffer less influence of human activities.…”

“…Altogether, they suggest an important role of plankton in São Tomé's reef food webs, such as has been reported for temperate rocky reefs (Truong, Suthers, Cruz, & Smith, ). Circumstantial evidence also suggests it might be the case of some marginal tropical isolated reef systems (e.g., Luiz et al, ; Quimbayo et al, ).…”

“…Important drivers highlighted so far include wave exposure (e.g., Friedlander, Brown, Jokiel, Smith, & Rodgers, ; Fulton & Bellwood, ; Fulton, Bellwood, & Wainwright, ), water temperature (e.g., Floeter, Behrens, Ferreira, Paddack, & Horn, ; Parravicini et al, ), depth (e.g., Brokovich, Einbinder, Shashar, Kiflawi, & Kark, ; Friedlander & Parrish, ), habitat topography and complexity (e.g., García‐Charton et al, ; Pinheiro et al, 2013; Wilson, Graham, & Polunin, ), benthic community cover (Ferreira, Gonçalves, & Coutinho, ; Friedlander & Parrish, ; García‐Charton et al, ) and interactions among species (Wisz et al, ). For example, it is generally acknowledged that shallow, sheltered and highly complex coral habitats host large abundances and high diversity of reef fishes (Dustan, Doherty, & Pardede, ; Gratwicke & Speight, ), whereas deeper areas in isolated places often contain high fish biomass (Friedlander, Sandin, DeMartini, & Sala, ; Khalil, Bouwmeester, & Berumen, ; Luiz et al, ). Moreover, the interplay between hydrodynamics and fish swimming ability (with its associated feeding performance) enables certain functional groups, like planktivores, to be more abundant in high‐wave exposure areas (Bellwood, Wainwright, Fulton, & Hoey, ; Floeter, Krohling, Gasparini, Ferreira, & Zalmon, ; McGehee, ; Wainwright, Bellwood, & Westneat, ).…”

Archipelago Los Roques: A potential baseline for reef fish assemblages in the southern Caribbean

“…Plankton feeder distribution at the archipelago scale was mainly explained by distance to shore (13.6%), dead coral cover (13.6%), reef type (11.8%), and the combination of slope and habitat heterogeneity (11.5%), reflecting the affinity of this trophic group for this sheltered habitat, which consisted of leeward and barrier reefs with important slope values, and thus short distances to shore. Plankton feeders such as Chromis multilineata and Chromis cyanea are usually associated with exposed windward habitats (Dominici‐Arosemena & Wolff, ; Floeter et al, ; Luiz et al, ; Mejía & Garzón‐Ferreira, ), but their high abundances along sheltered leeward steep slopes has also been reported for oceanic islands such as Bonaire and Curaçao (Sandin, Sampayo, & Vermeij, ) and Old Providence and Santa Catalina reef complex (Friedlander, Nowlis et al, ). Plankton feeders were most numerous along reef edges adjacent to deeper water, probably because their major prey is most accessible (Hobson, ).…”

“…Limiting the surveys to a similar depth reduced the variance in fish assemblage structure, since depth plays an important role in structuring reef fish assemblages (Arias‐González et al, ; Friedlander & Parrish, ; Luiz et al, ; McGehee, ). Exposure (18.5%) and reef type (10.7%) were the most important factors in explaining the overall distribution of reef fishes in the archipelago.…”