Abstract
Gelatinous organisms are key players of marine ecosystems, however underlying processes of their dynamics and behaviour are still to be cleared up. Understanding the areas of production, where the blooms go and what they become are therefore of major interest in marine ecosystem management. We used floating electronic tags developed in our laboratory for jellyfish live tracking. A special attention was put on the welfare of the organisms as the tag was floating and simply attached with a fishing line around the manubrium. In situ experiments were carried out in Bages Sigean lagoon (France) where a perennial population of the Mediterranean jellyfish Rhizostoma pulmo is established. Up to 47 deployments, from 20 min to 28h, took place in 2022 and 2023 summers. Live tracking indicated that the floating device did not influence the jellyfish trajectory nor its speed. A 28-hour trajectory showed that jellyfish movement can be influenced by the wind but also by other environmental factors. The relatively small area covered by the jellyfish compared to the control float one, suggests that movements significantly influence its trajectory as a response to the environment. Jellyfish were successfully recovered suggesting in a near future repeated individual measurements processes over longer deployments.