Case study in two seahorse sub populations in tropical estuaries
Channel: Encontro Recifal Brasileiro
Date: 2020-07-01

Tatiane Fernández do Carmo; Natalie Villar Freret-Meurer, Áthila Bertoncini Andrade, Luciano Neves dos Santos

Estuaries have many ecological importance to organisms and are characteristically dynamic environments. This characteristic could influence organisms and understand its consequences is extremely important to investigate if there are population patterns, especially for species that are threatened as the seahorse Hippocampus reidi. In that way, this study aimed to evaluate and compare the seasonal variation on the seahorse Hippocampus reidi subpopulations structure in two Rio de Janeiro coastal bays. Samplings were performed monthly during one year at rocky shores through free dives along four fixed transects. Seahorses detected were registered, measured and had their sex, reproductive stage, behavior and holdfast of occurrence identified. The results showed on dry season there was low precipitation, low temperature and high salinity, while in the rainy season it was the opposite. Despite this, there was no population structure response variation associated to these water variables. H. reidi exhibited low densities. The sex ratio varied on beaches, with males generally larger than females and larger Urca individuals than Duas Irmãs island. Females were found at similar depths as males at both sites, but on Urca seahorses were found deeper than Duas Irmãs. There were more adults relative to juveniles and males were more capture than female. Depth was the only factor which had seasonal variation, while there were not on other populations parameters analyzed on both areas. H. reidi were rare on beaches, which could indicate that these locations could have a passage function to this fish. All seahorses were reproductively active year around with spikes at rainy periods; also, were more recorded resting and seemed to anchor themself at seaweeds at both sites. This study demonstrates the water variables analyzed do not appear to be related to H. reidi populations. The subpopulations had similar population structures, with depth seasonality, contrasting with other population parameters.