Reef complexity as a driver of fine scale patterns of reef fish communities in Utila, Honduras

Abstract

The habitat variables of structural complexity and benthic composition are known to influence the health and biodiversity of coral reef ecosystems. In the past, these metrics were traditionally measured on site using highly invasive methodologies such as the chain and tape measure of rugosity. With anthropogenic disturbances threatening both the ability for coral to survive and for their structure to persist, this study employs the non-invasive and cost-effective tools of videography to assess the benthic composition and complexity of large sections of reef on the Caribbean island of Utila, Honduras. By building large-scale, detailed three-dimensional models it is possible to assess complexity using not only simple surface rugosity but also fractal dimensions at multiple resolutions. This research aims to: 1. Explore the correlations between benthic composition, structural complexity, and multiple fish community metrics with the aim of better understanding guild or scale-specific habitat preferences and 2. Assess the effectiveness of rugosity versus fractal dimension as measures of reef complexity using the methodology of three-dimensional structure-from-motion photogrammetry. This study succeeded at the large-scale three-dimensional modelling of six reef sites surrounding Utila, Honduras. Results showed a superior ability for fractal dimension measurements of reef complexity to characterize reef fish communities, with significant relationships between fractal dimensions at the scales of 15-5cm, 30-15cm, and 60-30cm to the metrics of total abundance, scale-specific abundance, biomass, herbivore biomass, and species richness. This study showed no significant correlations between rugosity or benthic cover to inhabiting fish communities.