Baseline study of the seahorse Hippocampus reidi Ginsburg, 1933 population in a tropical hypersaline lagoon

The present study investigated the occurrence of seahorses in Araruama hypersaline lagoon using a combination of rapid assessment surveys and data from citizen science. We conducted transects at each of the six study sites, where we recorded a series of population parameters. Local citizen scientists also provided records of occurrence through social media. A female-biased population of Hippocampus reidi Ginsburg, 1933 occupies the lagoon, where it reaches high densities. Most of the seahorses were found attached to artificial holdfasts, and ammonia and nitrite concentrations were above the level recommended by environmental agencies. The reports provided by the citizen scientists represented a valuable contribution to the database on the occurrence of seahorses around the lagoon. Our findings provide new insights into the biological potential of seahorses to colonize new areas and tolerate extreme conditions, as well as the importance of partnerships with citizen scientists to expand ecological knowledge.