Abstract

Permanent revision and adaptation of existing monitoring protocols are crucial to collecting data at the highest sampling precision with reduced cost, particularly during periods of rapid change and high losses driven by epizootic events. Different monitoring networks have used live coral cover, coral recruit density, fish abundance, and invertebrates as relevant indicators of coral reef health. Here, we focused on recruit density and the invertebrate community to answer a fundamental question: What is the best decision to sample with the highest precision and lowest time invested? Increase the size of the sampling unit, increase the number of sampling units, or both. For this, we conducted a field test with different observers repeating the same transect lines and varying the size and the number of sampling units usually used to determine the density of recruits and abundance of invertebrates. Our results indicate that doubling the size of recruit quadrats to 50 cm x 50 cm, and keeping the same number suggested by AGRRA, does not increase the time invested in the field and provides a more precise estimate of recruit density. Likewise, we demonstrate that doubling the transect length used to determine the density of invertebrates using the same width that AGRRA and the GCRMN propose, renders better estimates without significantly increasing time in the field. We conclude that pilot field studies to determine the best cost/effective sampling strategies will improve the precision of estimates of relevant variables used to determine the status of coral reefs in our current local context.