Static nets in motion: Evaluating seabed interactions of trammel nets deployed in two Mediterranean artisanal fisheries

Static fishing gears, such as trammel nets, are traditionally considered to have minor physical impact on benthic habitats and communities. However, some studies suggest notable but poorly quantified interactions with the seabed. This fact can be especially concerning when fishing occurs over complex and sensitive habitats, as is the case of fisheries targeting spiny lobster ( Palinurus elephas ) in the Mediterranean. Understanding these interactions is crucial for assessing ecological impacts and promoting sustainable practices in small-scale fisheries. This study evaluated the interaction of the trammel nets targeting cuttlefish ( Sepia officinalis ) and spiny lobster with the seagrass Posidonia oceanica and rhodolith bed (i.e., formed by nodules of coralline red algae) habitats, respectively, using underwater time-lapse cameras, motion sensors, GPS, and catch data. The results confirmed that nets remained static during the soaking, but caused considerable displacement and collapse over the seabed during hauling. These processes increased the contact surface, leading to organism displacement and entanglement. Interaction area between nets and seabed significantly increased with the depth and net length; however, shorter nets generated larger interaction areas when standardized by netting walls. Entanglement of P. oceanica in cuttlefish fishing increased with interaction area, while no such pattern was observed for rhodoliths in lobster fishing, likely due to habitat heterogeneity. The acquired knowledge in this study about the interactions between trammel nets and sensitive benthic habitats facilitates the assessment of fishing impacts and the development of mitigation measures in conservation-focused areas. • Using underwater cameras, motion sensors, and GPS to study mobility in static nets. • Nets remain static during the soak time, without displacement caused by currents. • Nets displace considerably and collapse over the seabed during the hauling process. • Sensitive habitats as Posidonia seagrass and rhodolith beds may be affected by nets. • Knowledge of nets interactions helps fisheries coexist sustainably with habitats.