A survey of fishes associated with Hawaiian deep-water Halimeda kanaloana (Bryopsidales: Halimedaceae) and Avrainvillea sp. (Bryopsidales: Udoteaceae) meadows.

Ross C Langston,Heather L Spalding

doi:10.7717/peerj.3307

Ross C Langston, Heather L Spalding

Open Access

https://doi.org/10.7717/peerj.3307

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Abstract

The invasive macroalgal species Avrainvillea sp. and native species Halimeda kanaloana form expansive meadows that extend to depths of 80 m or more in the waters off of O‘ahu and Maui, respectively. Despite their wide depth distribution, comparatively little is known about the biota associated with these macroalgal species. Our primary goals were to provide baseline information on the fish fauna associated with these deep-water macroalgal meadows and to compare the abundance and diversity of fishes between the meadow interior and sandy perimeters. Because both species form structurally complex three-dimensional canopies, we hypothesized that they would support a greater abundance and diversity of fishes when compared to surrounding sandy areas. We surveyed the fish fauna associated with these meadows using visual surveys and collections made with clove-oil anesthetic. Using these techniques, we recorded a total of 49 species from 25 families for H. kanaloana meadows and surrounding sandy areas, and 28 species from 19 families for Avrainvillea sp. habitats. Percent endemism was 28.6% and 10.7%, respectively. Wrasses (Family Labridae) were the most speciose taxon in both habitats (11 and six species, respectively), followed by gobies for H. kanaloana (six species). The wrasse Oxycheilinus bimaculatus and cardinalfish Apogonichthys perdix were the most frequently-occurring species within the H. kanaloana and Avrainvillea canopies, respectively. Obligate herbivores and food-fish species were rare in both habitats. Surprisingly, the density and abundance of small epibenthic fishes were greater in open sand than in the meadow canopy. In addition, species richness was also higher in open sand for Avrainvillea sp. We hypothesize that the dense holdfasts and rhizoids present within the meadow canopy may impede benthic-dwelling or bioturbator species, which accounted for 86% and 57% of individuals collected in sand adjacent to H. kanaloana and Avrainvillea sp. habitats, respectively. Of the 65 unique species recorded in this study, 16 (25%) were detected in clove oil stations alone, illustrating the utility of clove-oil anesthetic in assessing the diversity and abundance of small-bodied epibenthic fishes.

Highlights

Macroalgal meadows constitute important habitats for reef- and nearshore fish species
Few studies have investigated the fauna of mesophotic macroalgae, despite the fact that several meadow-forming species occur at depths of 50 m or more in tropical and subtropical waters (Huisman, Abbott & Smith, 2007; Spalding, 2012; Pyle et al, 2016)
We describe the fish fauna associated with two deep-water macroalgal species, Avrainvillea sp. and Halimeda kanaloana, from Hawaiian waters

Summary

Introduction

Macroalgal meadows constitute important habitats for reef- and nearshore fish species. Relative to surrounding habitats, which are often sandy and of low-relief, macroalgal meadows constitute highly-complex and rugose habitats which may afford protection to juvenile and small-bodied reef fish species alike. Recent work has focused on the mesophotic zone, which extends from 30 to 150 m (Hinderstein et al, 2010). Much of this work has focused on coral reef habitats and their associated fauna. Few studies have investigated the fauna of mesophotic macroalgae, despite the fact that several meadow-forming species occur at depths of 50 m or more in tropical and subtropical waters (Huisman, Abbott & Smith, 2007; Spalding, 2012; Pyle et al, 2016)

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