A comparison of diver vs. acoustic methodologies for surveying fishes in a shallow water coral reef ecosystem

Studies show worldwide declines in coral reef community health and fish density, however, evidence of decline on limited spatial scales may mask reef-wide patterns. New methods are necessary to investigate reef communities at greater spatial and temporal scales. We examined fish densities derived by concurrent diver and acoustic surveys on a series of linear relict reef lines in southeastern Florida, USA. Fish density estimates displayed differences in magnitude, but similar patterns across independent sampling units. Estimates of fish lengths derived by both methods suggest that a seasonal increase in size occurred across the surveyed reefs. The efficacy of diver-based surveys declined with increasing visibility, while acoustic survey results remained insensitive to changes in water column visibility. Results between survey methods correlate statistically, suggesting that studies may utilize combined methods to investigate fish density distributions on large spatial scales not typically examined.