Influence of environmental variables on activity patterns of the Dusky Grouper (Epinephelus marginatus) assessed through a novel acoustic telemetry approach

Abstract

[eng] The study of the influence of environmental factors on the activity patterns of marine species is considered a relevant issue for a deeper understanding of their ecology. The dusky grouper (Epinephelus marginatus) is one of the most emblematic species and one of the most important coastal predators in the Mediterranean Sea. Using a novel approach that combines acoustic telemetry and Hidden Markov Models (HMMs) in a Marine Protected Area, adult groupers were tracked to correlate changes in their activity with environmental factors such as lunar phase, day/night cycle, and temperature before and during the reproductive period. The new methodological approach was based on the use of a single receiver to differentiate between two behavioral states of activity (Resting vs. Active) based on the time of arrival of the signal from the transmitter to the receiver (TOA), the distance traveled by the individuals, and the application of HMM to estimate probability of transition between them. Results showed that E. marginatus is a predominantly inactive species. We found a direct correlation between its active phases and the reproductive periods, including environmental variables such as the temperature, although it seems that its effect varies greatly among individuals. Our results aim to deepen the understanding of the ecology of this important species, contributing to its conservation and providing management strategies for the MPA. The study highlights the importance of advanced telemetry techniques and sophisticated analytical models in marine research, offering valuable insights into the behavior of this species in relation to environmental factors.