Highly diverse mesophotic reef fish communities in Raja Ampat, West Papua

Abstract

Mesophotic coral ecosystems (MCEs; reefs 30–150 m depth) are poorly studied, with existing research heavily geographically biased away from the most species-rich reef regions. Yet, MCEs are of high interest because of their unique species and potential to act as refuges from the impacts of fishing. Using baited remote underwater video systems, we surveyed reef fish communities from 2 to 85 m depths throughout the Raja Ampat archipelago in West Papua, Indonesia—an area considered the heart of the Coral Triangle where coral reef biodiversity is greatest. We sought to provide the first assessment of fish communities across this depth gradient in the region and identify whether human population density and market access differently affected fish abundance based on depth. Here we show that—similar to shallow reefs—Raja Ampat MCEs are exceptionally diverse, with 152 fish species recorded at depths greater than 40 m. We found that fish community structures were highly depth driven, with declines in fish abundance at increased depth. In contrast to previous studies elsewhere in the world, we found that the proportion of planktivores declined across the shallow reef to MCE depth gradient. While greater human population density correlated with lower Epinephelidae and Lutjanidae abundance (two key fisheries families), we did not find evidence that MCEs provide a depth refuge from fishing. Surprisingly, we also found that fish abundance declined at greater distances from the major regional market—likely caused by historical fisheries pressure in more remote areas. These results both expand upon and contrast some previously established MCE-depth patterns and human impact patterns on fish communities, suggesting that regional context and historical pressures matters. Our findings highlight the need for future MCE studies within the Coral Triangle region.

The importance of biophysical context in understanding marine protected area outcomes for coral reef fish populations

“…Interestingly, distance to markets demonstrated negative effects, with the biomass of Acanthurids, Lethrinids, and Serranids increasing in reefs closer to market centers. Although this contrasts with global studies (Cinner et al 2012), it is congruent with recent studies of fish populations in Raja Ampat (Andradi-Brown et al 2021). The effects of landbased markets may have been reduced by large freezerequipped vessels that frequented many of our control sites up until 2014, thereby serving as temporary market centers.…”

Environmental DNA highlights fish biodiversity in mesophotic ecosystems

“…They are found in subtropical, tropical, and temperate regions at depths ranging from approximately 30 to 150 m below the sea surface depending on water clarity (Loya et al, 2016;Loya, 2019). MEs support high biodiversity (Andradi- Brown et al, 2021), including species restricted and specialized to the mesophotic zone but also sharing species with their shallower counterparts (e.g., Lesser et al, 2019;Rocha et al, 2018;Soares et al, 2018). Sampling in these areas is difficult due to the presence of hard bottom at this depth range which limits the use of traditional methods such as scuba diving or grabs and trawls.…”

“…Mesophotic ecosystems are galvanizing research interest, both because of their unique biodiversity from invertebrates to fishes (Andradi-Brown et al, 2021;Lesser et al, 2019), but also because of their potential to act as refugia for shallow-water species from anthropogenic disturbances (Bongaerts et al, 2010). It was widely assumed that MEs have a reduced vulnerability to threats because of their remoteness and depth and could therefore sustain fish populations that are eroding on surface reefs (Eyal & Pinheiro, 2020;Laverick et al, 2016;.…”

The Bird's Head Seascape Marine Protected Area network—Preventing biodiversity and ecosystem service loss amidst rapid change in Papua, Indonesia

“…While remote Indonesian reefs generally have higher fish biomass (Campbell et al, 2020), remoteness is unlikely responsible for BHS MPA outcomes. Fishers from other Indonesian provinces and neighboring countries travel large distances to access the rich fishing grounds within the BHS (e.g., Jaiteh et al, 2016), and some more remote sites within the BHS have lower fish abundance than those closer to major cities (Andradi‐Brown et al, 2021). Our results suggest that, overall, MPAs are leading to positive coral reef outcomes, and can help inform adaptive management for ongoing regional fisheries challenges for the BHS.…”