AUTHOR=Spatafora Davide , Gristina Michele , Quattrocchi Federico , Pierri Cataldo , Lazic Tamara , Palma Jorge 

TITLE=Different behavioral strategies of two sympatric seahorses: habitat availability and increased density of Hippocampus guttulatus alter the behavior of Hippocampus hippocampus

JOURNAL=Frontiers in Marine Science

VOLUME=Volume 10 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2023.1138296

DOI=10.3389/fmars.2023.1138296

ISSN=2296-7745

ABSTRACT=Ocean warming and habitat fragmentation are becoming increasingly stressful upon coastal fishes. Therefore, fishes must adjust their physiological and behavioural traits to face the combined effect of global warming and ecological interactions. Seahorses (Hippocampus spp.) are charismatic fishes with peculiar life cycle traits which makes them vulnerable to several anthropic pressures and natural disturbances. In this study, we investigated the behaviour of two sympatric seahorse species, the long-snouted Hippocampus guttulatus (Cuvier, 1829) and the short-snouted Hippocampus hippocampus (Linnaeus, 1758). Specifically, we carried out two manipulative experiments to assess i) the effect of temperature and habitat availability on both H. hippocampus and H. guttulatus behaviour, and ii) the effect of temperature and an increased density of H. guttulatus (by 3X) on the activity level of congeneric species H. hippocampus. Our results showed that +3 °C warming did not affect seahorse behaviour in both experiments suggesting greater behavioural tolerance to thermal variation. However, a significant reduction of the active behaviour of H. hippocampus was observed when the artificial habitat was introduced in the tank, while H. guttulatus maintained its activity. Furthermore, a significant decrease of the H. hippocampus activity was observed with an increased relative dominance of H. guttulatus. Our results suggest that both increased density of H. guttulatus and habitat availability, but not ocean warming, will affect the behaviour of H. hippocampus. Therefore, different interspecific behavioural strategies may occur thus affecting the distribution of the two species among shallow habitats when they occur in sympatry.