Shining a light on the composition and distribution patterns of mesophotic and subphotic fish communities in Hawai‘i

Abstract

As agencies shift from single-species management to ecosystem-based fisheries management, ecosystem models are gaining interest for understanding species dynamics in relation to oceanographic and ecological processes and human marine uses. However, information on community structure or distribution of many species that occupy deep (> 30 m) waters is largely unavailable. We amassed a total of 24 686 fish observations of 523 species/taxa for the 30−410 m depth areas surrounding the main Hawaiian Islands (MHI). We also obtained estimates of geomorphological variables, including substrate type, slope, rugosity, and ridge-like features. Using these 2 data sources, we (1) identified distinct fish communities along the 30−410 m depth gradient, and (2) generated relative biomass maps for fish functional groups. We showed that the mesophotic zone ranges between 30 and 129 m, with a fish faunal break at 60 m. Beyond this zone, 4 subphotic zones were identified: upper rariphotic (130−169 m), mid-rariphotic (170−239 m), lower rariphotic (240−319 m), and upper bathyal (320−410 m). We assigned fish species to functional groups partly based on identified depth ranges and fitted general additive models (GAMs) integrating geomorphological covariates to the functional group relative biomass estimates to determine the environmental variables that best predict the probability of encounter and relative biomass of each fish functional group. Finally, GAM predictions were employed to map functional group relative biomass distributions. These distribution maps showed a high relative biomass of many groups in the center of the MHI chain. This study contributes to a better understanding of fish community structure around the MHI and will inform ecosystem model parameterization.

Fish biodiversity patterns of a mesophotic-to-subphotic artificial reef complex and comparisons with natural substrates

“…Depth did primarily control variations in species composition, including an apparent faunal break from 113-139 m (Fig 3). This finding is consistent with Pyle et al [8,14,38]. These faunal breaks have at times been speculated to be related to the depth at which light becomes insufficient for photosynthesis [9].…”

“…In certain areas, one major mesophotic split in reef fish communities has been identified between 50-60 m [9,10]. In Hawaii, though, perhaps due to the exceptionally clear waters [11], there are strong indications that another principal transition occurs between 110-140 m [8,13,14]. It is not known how these changes might affect artificial reefs, given that their physical structure is not dependent on available light, or whether artificial communities may exhibit faunal breaks that resemble those on natural substrates.…”

Environmental and Structural Drivers of Fish Distributions among Petroleum Platforms across the U.S. Gulf of Mexico

“…; Weijerman et al. ). As another conservative measure, we excluded species that were encountered on < 10% of survey events (i.e., rare species) to help ensure that the results were based on sufficient data.…”

“…2018a, ; Dance and Rooker ; Weijerman et al. ), we employed a standard collinearity analysis to exclude those environmental variables that are strongly correlated with others or with eastings and northings from horizontal and vertical distribution GAMMs (Leathwick et al. ; Dormann et al.…”

“…() and Weijerman et al. () and evaluated all horizontal distribution and vertical distribution GAMMs using the data sets internal to their development. For each study species, 1,000 bootstrap data sets were generated by resampling with replacement from the horizontal distribution data set and 1,000 other bootstrap data sets were generated by resampling with replacement from the vertical distribution data set, and horizontal distribution and vertical distribution GAMMs were then fit to bootstrapped data sets.…”