DOI: 10.5061/dryad.wh70rxwkf
title: Dominance of endemics in the reef fish assemblages of the Hawaiian Archipelago

description: Aim: Species ranges provide a valuable foundation for resolving
 biogeographic regions, evolutionary processes, and extinction risks. To
 inform conservation priorities, here we develop the first
 bioregionalization based on reef fish abundance of the Hawaiian
 Archipelago, which spans nearly 10° of latitude across 2,400 km, including
 8 high volcanic islands in the populated main Hawaiian Islands (MHI), and
 10 low islands (atolls, shoals, and islets) in the remote northwestern
 Hawaiian Islands (NWHI).. Location: The Hawaiian Archipelago. Taxon:
 Fishes (276 taxa). Methods: We compiled 5,316 visual fish surveys at
 depths of 1-30 m from throughout the Hawaiian Archipelago. Geographic
 range (km2) for each species was measured as extent of occurrence (EOO)
 and area of occurrence (AOO). PERMANOVA and PCO were used to investigate
 drivers of fish assemblage structure. Distance-based multivariate analyses
 were used to evaluate the relationship between fish assemblage structure
 and predictor variables including latitude, reef area, temperature,
 chlorophyll-a, wave-energy, and human population density. Results:
 Distinct fish assemblages exist in the MHI and NWHI, with two additional
 faunal breaks driven primarily by endemic species abundance. Latitude
 explained 37% of the variability in fish assemblages, with reef area
 accounting for an additional 9%. EOO showed a significant correlation with
 latitude. Endemics comprised 52-55% of the numerical abundance at the
 northern end of the archipelago but only 17% on Hawai‘i Island in the
 extreme south. Maximum size and activity regime (day vs. night) explained
 the most variation in the abundance of endemics. Main conclusions: The
 Hawaiian fish assemblages are strongly influenced by endemic species,
 affirming the archipelago as a biodiversity hotspot of high conservation
 value. The higher abundance of endemics in the NWHI may represent
 preadaptation to oceanic (oligotrophic) conditions. Resolution of distinct
 bioregions across the archipelago provides a better understanding of reef
 fish macroecology, with implications for management at the archipelago
 scale.
description: Fish surveys were conducted throughout the Hawaiian Archipelago
 from 2007 to 2016 by the US National Oceanic and Atmospheric
 Administration’s Ecosystem Sciences Division, using a stratified random
 sampling design (Heenan et al., 2017). A total of 5,316 surveys were conducted
 at 2,108 locations, across a depth range of 1 – 30 m. Only
 forereef locations were used to control for differences in habitat types.
 Each survey consisted of 2 divers, collecting data at adjacent survey
 areas using a modification of the paired stationary point count (SPC)
 method (Heenan et al., 2017). For the SPC, the divers conducted
 simultaneous counts in estimated 15 m diameter cylinders extending from
 the substrate to the limits of vertical visibility. Each SPC consisted of
 two components: a 5-minute species enumeration period in which divers
 recorded all species present or moving through their cylinder, followed by
 a tallying portion, in which divers systematically recorded the number and
 size (total length to nearest cm) of each taxon on their list. The
 tallying portion was conducted as a series of rapid visual sweeps, with
 one species grouping counted per sweep. Heenan, A., Williams, I.D.,
 Acoba, T., DesRochers, A., Kosaki, R.K., Kanemura, T., Nadon, M.O.
 & Brainard, R.E. (2017). Long-term monitoring of coral reef fish
 assemblages in the Western central pacific. <i>Scientific
 Data</i>, <i>4</i>(1), 1-12.