Assessing the value of citizen scientist observations in tracking the abundance of marine fishes

The state of biodiversity for most of the world is largely enigmatic due to a lack of long-term population monitoring data. Citizen science programs could substantially contribute to resolving this data crisis, but there are noted concerns on whether methods can overcome the biases and imprecision inherent to aggregated opportunistic observations. We explicitly test this question by examining the temporal correlation of population time-series estimated from opportunistic citizen science data and a rigorous fishery-independent survey that concurrently sampled populations of coral-reef fishes (n = 87) in Key Largo, Florida, USA, over 25 years. The majority of species exhibited positive temporal correlations between population time-series, but survey congruence varied considerably amongst taxonomic and trait-based groups. Overall, these results suggest that citizen scientists can be effective sentinels of ecological change, and that there may be substantial value in leveraging their observations to monitor otherwise data-limited marine species.