## 4 Discussion  
The present study has compared the conservation state of rhodoliths beds in four areas of the Site of Community Importance Menorca Channel, subjected to different levels of bottom trawl fishing effort. The results have shown clear differences in the composition and diversity of epibenthic communities, as well as in the size and morphology of the rhodolith species analyzed, due to the impact of bottom trawl fishing activity. Areas located in the central part of the Menorca Channel (Non-impacted and Low effort history) showed differences in seafloor bathymetry, sediment type, and velocity of bottom currents compared to areas located in the southern part (Medium effort history and High effort). Light is considered one of the most important environmental factors influencing the distribution of benthic organisms on the continental shelf [29; 51; 52], to \begin{table}
\begin{tabular}{c c c} \hline \hline
**Low Effort History** & \(\boldsymbol{n/30^{\prime}}\) & **se** \\ \hline _Ophitura ophitura_ & 5.7 & 2.9 \\ _Paguridae_ & 5.2 & 4.6 \\ _Echinaster sepositus_ & 2.8 & 1.4 \\ _Ascidia mentula_ & 2.3 & 1.1 \\ _Dardanus arrosor_ & 2.3 & 1.6 \\ _Pagurus prideauxi_ & 1.7 & 1.7 \\ _Parastichopus regalis_ & 1.3 & 0.6 \\ _Aplidium spp._ & 1.0 & 0.5 \\ _Subertrics domuncula_ & 0.7 & 0.3 \\ _Aequipcetn opercularis_ & 0.7 & 0.4 \\ _Molgula appendiculata_ & 0.7 & 0.7 \\ _Inachus thoracicus_ & 0.7 & 0.4 \\ _Marthasterias glacialis_ & 0.5 & 0.3 \\ _Phallus maummilata_ & 0.5 & 0.5 \\ _Pleurbranchia neckeli_ & 0.5 & 0.5 \\ _Botrylins schlosseri_ & 0.5 & 0.5 \\ \hline \hline
**Medium effort history and High effort** & \(\boldsymbol{n/30^{\prime}}\) & **se** \\ \hline _Dardanus arrosor_ & 14.8 & 2.7 \\ _Spatangus purpureus_ & 9.9 & 3.1 \\ _Sphaerechinus granularis_ & 8.3 & 4.3 \\ _Subertrics domuncula_ & 8.3 & 2.3 \\ _Pagurus prideaux_ & 5.7 & 4.8 \\ _Echinaster sepositus_ & 2.8 & 0.6 \\ _Ascidia mentula_ & 2.4 & 1.1 \\ _Paguridae_ & 1.9 & 0.8 \\ _Inachus spp._ & 1.5 & 0.9 \\ _Ascidia virginia_ & 1.0 & 0.7 \\ _Aequipcetn opercularis_ & 0.9 & 0.4 \\ _Phallusa mummilata_ & 0.8 & 0.4 \\ _Polycarpa mammilaris_ & 0.8 & 0.5 \\ _Ophitura ophitura_ & 0.7 & 0.3 \\ _Parastichopus regalis_ & 0.6 & 0.4 \\ _Diazom violacea_ & 0.5 & 0.3 \\ _Aplidium spp._ & 0.5 & 0.2 \\ _Ophitura spp._ & 0.5 & 0.3 \\ _Luidia ciliaris_ & 0.5 & 0.4 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Average values of abundance, in terms of individuals (\(n\)) per 30 min of fishing, of the main epibenthic species caught in commercial hauls, estimated from the sampling of scientific observers on board the trawling fleet in the Low effort history area, as well as in the Medium effort history and High effort areas, considered in the present study. gether with sediment type [53; 54; 55; 56; 57; 58; 59; 60]. In fact, the decreases in light irradiance and bottom currents velocities with depth have been argued as factors explaining the morphology and distribution of rhodolith species [20; 22; 61]. Burial and reduction of live rhodoliths increase in substrates with a high proportion of fine sediment [62; 63]. On the other hand, the effects of bottom trawling on epibenthic communities lead to changes in community structure and biodiversity [20; 64; 65; 66; 67], also changing the composition and morphology of rhodoliths beds [20; 21; 22]. The comparison of all the areas between them could mask the effect of bottom trawling, due to the strong variability that causes the environmental conditions on the epibenthic communities analyzed. In order to block it, we compared similar environmental scenarios: (i) Non-impacted was compared to its adjacent Low effort history area; and (ii) Medium effort history was compared to its adjacent High effort area. The higher similarity among samples within Medium effort history and High effort areas than among the Non-impacted and Low effort history areas also points to a homogenization effect of bottom trawling on epibenthic communities.