Determinants of reef fish assemblages in tropical Oceanic islands

Abstract

Diversity patterns are determined by biogeographic, energetic, and anthropogenic factors, yet few studies have combined them into a large‐scale framework in order to decouple and compare their relative effects on fish faunas. Using an empirical dataset derived from 1527 underwater visual censuses (UVC) at 18 oceanic islands (five different marine provinces), we determined the relative influence of such factors on reef fish species richness, functional dispersion, density and biomass estimated from each UVC unit. Species richness presented low variation but was high at large island sites. High functional dispersion, density, and biomass were found at islands with large local species pool and distance from nearest reef. Primary productivity positively affected fish richness, density and biomass confirming that more productive areas support larger populations, and higher biomass and richness on oceanic islands. Islands densely populated by humans had lower fish species richness and biomass reflecting anthropogenic effects. Species richness, functional dispersion, and biomass were positively related to distance from the mainland. Overall, species richness and fish density were mainly influenced by biogeographical and energetic factors, whereas functional dispersion and biomass were strongly influenced by anthropogenic factors. Our results extend previous hypotheses for different assemblage metrics estimated from empirical data and confirm the negative impact of humans on fish assemblages, highlighting the need for conservation of oceanic islands.

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

“…Additionally, oceanic systems receive very little sediment input from continental landmasses and, as such, conserve clear waters that are adequate for the feeding activity of these planktivores fishes (Johansen & Jones, 2013). As a result, most oceanic islands are dominated by reef planktivores, despite differences in fishing pressure (e.g., Friedlander et al, 2010;Krajewski & Floeter, 2011;Luiz et al, 2015;Quimbayo et al, 2017;Quimbayo et al, 2018). Our results, showing both a pivotal role of wave exposure in shaping reef fish assemblages and a numerical and biomass dominance of planktivores at São Tomé Island are consistent with this scenario.…”

“…In the last 15 years, studies focused on oceanic islands have revealed remarkable features, such as unusual high fish biomass and peculiar benthic communities (e.g., Sandin et al, 2008;Stevenson et al, 2007;Williams et al, 2013;Quimbayo et al, 2018). The high abundance and biomass of large predators and herbivorous species in these isolated systems contrasts with more accessible reef systems (Friedlander et al, 2003(Friedlander et al, , 2010Graham & McClanahan, 2013;Morais, Ferreira, & Floeter, 2017;Williams et al, 2015).…”

“…These ob- showing that human-related variables explain reef fish assemblage biomass around the world (Bellwood, Hoey, & Hughes, 2012;Cinner, Graham, Huchery, & Macneil, 2013;Mora et al, 2011;Williams et al, 2015). However, most studies addressing the structure of fish (and benthic) assemblages in tropical oceanic islands have been performed in the Indo-Pacific (Sandin et al, 2008;Williams et al, 2013), in the southwestern Atlantic (Krajewski & Floeter, 2011;Longo et al, 2015;Luiz et al, 2015;Pinheiro, Ferreira, Joyeux, Santos, & Horta, 2011) or in the Tropical Eastern Pacific (e.g., Edgar et al, 2011;Friedlander et al, 2012;Quimbayo, Mendes, Kulbicki, Floeter, & Zapata, 2017;Quimbayo et al, 2018). In comparison, fish assemblages from the Tropical Eastern Atlantic (TEA) remain poorly explored apart from species checklists (Afonso et al, 1999;Wirtz et al, 2013Wirtz et al, , 2007.…”

The omnivorous triggerfish Melichthys niger is a functional herbivore on an isolated Atlantic oceanic island

“…Oceanic islands are often considered natural laboratories, where anthropogenic effects on native communities are absent or less pronounced than on continents (Sandin et al ., ; Quimbayo et al ., ). Features such as distance from the mainland and island size and age can affect colonisation and extinction rates on oceanic islands, driving patterns of richness and endemism in marine communities (Hachich et al ., ; Pinheiro et al ., ).…”

Fish biodiversity of Saint Peter and Saint Paulʼs Archipelago, Mid‐Atlantic Ridge, Brazil: new records and a species database

“…The increase in the depth range of scientific exploration is contributing to a better understanding of the distribution of the world's marine biodiversity and accelerating the rate of knowledge acquisition about the distributions and biogeographical patterns of marine organisms. For instance, despite being considered a cosmopolitan species, there were few records for the chondrichthyan Odontaspis ferox (Risso, 1810) in the southwestern (Fergusson et al, 2008;Graham et al, 2016;Long et al, 2014) Despite the isolation and small area of SPSPA, the richness of the fish species is similar to that recorded for other larger islands of the SA (Pinheiro et al, 2015;Quimbayo et al, 2019;Soto, 2001) and MAR (Wirtz et al, 2017), and should keep increasing with further studies, based on the species accumulation curves and low overlap between adults and larvae records ( Figure 5). This relatively high fish richness level recorded for SPSPA is a consequence of extensive sampling on Thus, it is believed that additional deep exploration and sampling effort in SPSPA might reveal more endemic and undescribed deep-sea species.…”