Abstract

The current state of biodiversity remains largely enigmatic for most species and regions on Earth due to a severe lack of long-term ecological monitoring data. Citizen science programs could substantially contribute to resolving this biodiversity data crisis, but there are noted concerns regarding whether analytical methods can overcome the biases and imprecision inherent to aggregated opportunistic ecological data. We explicitly test this question by examining the congruence of population time-series estimated from data collected through an opportunistic citizen science program and a rigorous fishery-independent survey that concurrently sampled populations of coral reef fishes (n = 87) in Key Largo, Florida, USA, over 25 years. We used a multivariate state-space modelling framework to explicitly measure the correlation in year-to-year changes in abundance between species’ population abundance time-series from each survey. While congruence between survey time-series varied considerably among species, we found an overall positive correlation between surveys (median ρ = 0.38). Our findings demonstrate that citizen scientists can be effective sentinels of ongoing ecological change, and that there may be substantial value in leveraging their observations to monitor otherwise data-limited populations of marine species.