Journal de biologie marine et d'océanographie

Human-Driven Effect on the Escape Responses of Two Commercially Important Coastal Fish Species

Gabriele La Mesa, Sabrina Agnesi, Eva Salvati and Leonardo Tunesi

Human-Driven Effect on the Escape Responses of Two Commercially Important Coastal Fish Species

Objective: In this study we investigated the behavioral responses of two coastal Mediterranean sea breams (Diplodus sargus and Diplodus vulgaris) to the potential threat represented by an approaching diver. Methods: Fish reaction to diver presence was assessed using flight initiation distance (FID) as behavioral metric. During each scuba diving trial, we also recorded i) fish size and group size, ii) fish behavior before and after the flight, iii) the abiotic context (depth and bottom slope) at the sighting location. Results: Our results indicated that FID of D. sargus, which is more heavily targeted by spearfishers, was higher than that of D. vulgaris. In both species, no significant linear relationships between FID and body size, group size and depth were detected. The preflight behavioral patterns exhibited by these species were quite similar. “Tacking” was the most common behavior observed where fish halted activity and slowly swam away from the observer. The escape in open water was the most frequently adopted post-flight behavior by both species. The proportion of fish hiding into a shelter after fleeing was higher in D. sargus than D. vulgaris. Conclusion: The knowledge of the human-driven modifications in the behavior of sea breams and other exploited species using FID measurements is a valuable tool to inform management about the impact of certain anthropic activities (e.g. spearfishing) on these resources and to assess the effectiveness of enforced protection measures.