Trophic designation and live coral cover predict changes in reef-fish community structure along a shallow to mesophotic gradient in Hawaii

Abstract

Reef-fish community structure and habitat associations are well documented for shallow coral reefs (\20 m) but are largely unknown in deeper extensions of reefs (mesophotic reefs; [30 m). We documented the community structure of fishes and seafloor habitat composition through visual observations at depth intervals from 3 to 50 m in West Hawaii. Community structure changed gradually with depth, with more than 78% of fish species observed at mesophotic depths also found in shallow reef habitats. Depth explained 17% of the variation in reef-fish community structure; live coral cover explained 10% and prevalence of sand accounted for 7% of the fitted variation indicating that depth-related factors and coral habitat play a predominant role in structuring these communities. Differences in community structure also appear to be linked closely with feeding behavior. Trophic designation accounted for 31% of the fitted variation, with changes in herbivore abundance accounting for 10% of the variation. These findings suggest that changes in reef-fish community composition from shallow to mesophotic environments are largely influenced by trophic position, coral habitat and indirect effects of depth itself.

Depth-Dependent Structuring of Reef Fish Assemblages From the Shallows to the Rariphotic Zone

“…This study combined diver and submersible surveys of the Bermuda slope and the flank of Plantagenet Bank to investigate fish assemblages covering a depth range from 15 to 305 m by incorporating both abundance and biomass data, the latter of which are rarely collected from underwater video surveys. As has been found in other studies from shallow and mesophotic reefs (e.g., Fukunaga et al, 2016;Lindfield et al, 2016;Kane and Tissot, 2017;Rocha et al, 2018), the fish assemblages of Bermuda and Plantagenet Bank showed strong depth-dependent structuring.…”

“…Aided by advances in technical diving technology, recent biodiversity assessments of MCEs demonstrated that the upper MCEs (∼30-60 m) harbor biologically unique fish faunas with varying degrees of taxonomic overlap with shallower reef assemblages (Bejarano et al, 2014;Kane and Tissot, 2017;Semmler et al, 2017;Rocha et al, 2018). The magnitude of taxonomic overlap and the cut-off depth at which faunal breaks occur vary by location and are likely determined by a combination of local and regional, contemporary and historic environmental drivers and anthropogenic activities (Laverick et al, 2017).…”

Spatial variability in reef‐fish assemblages in shallow and upper mesophotic coral ecosystems in the Philippines

“…However, despite location differences, consistent patterns were observed between depths such as the decrease in species richness and the increase in biomass. This is a similar pattern exhibited in the transition between shallow and upper MCEs in many parts of the world (Abesamis et al, ; Andradi‐Brown et al, ; Bejarano et al, ; Kane & Tissot, ; Lindfield et al, ; Pinheiro et al, ). Also, it seems that despite the depth differences caused by benthic cover and inaccessibility to certain fishing methods, the dissimilarity caused by location has a stronger effect compared with depth.…”

Deep-Reef Fish Communities of the Great Barrier Reef Shelf-Break: Trophic Structure and Habitat Associations

“…However, a number of potential interactions between habitat characteristics and the associated fish community have been identified. For example, studies of fish assemblages from tropical Indo-Pacific and Atlantic shelf-breaks have reported the partitioning of trophic groups with depth [2,8,26,30,[32][33][34][35][36]. With increasing depth, the abundance of herbivores decreases and the abundance of planktivores increases [37].…”

“…The distribution of these benthic organisms is often highly depth-dependent. For instance, scleractinian corals are generally the most important component of shallower communities [2,34,36], while the representation of heterotrophic taxa such as sponges and gorgonians increase with depth as light decreases [26,39]. Similarly, other studies have suggested that physical attributes of the underlying benthos that increase habitat complexity, such as overall rugosity or the presence of key elements such as boulders or bedrock, often affects fish abundance [30], even in the absence of habitat-forming sessile invertebrates and algae.…”