Appraisal of visual assessments of habitat complexity and benthic composition on coral reefs
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Visual assessments of topographic habitat structure and benthos on coral reefs were appraised using quantitative data collected from 16 replicate surveys within each of 21 sites on Seychelles reefs. Results from visual assessments of reef benthos were similar to those obtained using techniques frequently used to assess benthic complexity and composition. Visual estimates of habitat topography were correlated with rugosity, reef height and holes of 10–70 cm diameter, whilst visual estimates of benthic composition were very similar to those obtained from line intercept transects. Visual estimates of topography correlated strongly with species richness of fish communities and explained 42% of the variation in these data. The relationship between visual estimates of topography and species richness is strongest with fish 10–30 cm total length (TL), abundance of fish within this size category also correlating positively with topographic visual assessments. Visual techniques are prone to observer bias, however with regular training they can be used to quickly provide a reliable and effective means of assessing habitat complexity and benthos on coral reefs.
KeywordsCoral Reef Fish Community Coral Cover Complexity Measure Habitat Complexity
We thank the Seychelles Centre for Marine Research and Technology-Marine Parks Authority, Seychelles Fishing Authority and Nature Seychelles for logistical support and M. Chang-Leng, A. Cheal, M. Emslie, I. Miller and F. Ravina for their assistance in the field. Early drafts of the manuscript were improved by comments from M. Emslie and R. Fisher. S. Delean and R. Fisher provided statistical advice. This work was supported by grants from the Leverhulme Trust and the Western Indian Ocean Marine Science Association (WIOMSA).
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