Assessing the hidden threat of removing abandoned fishing gear from coralligenous habitats: a new monitoring protocol

Fishing gear poses a serious threat to coralligenous habitat, causing several damages both during fishing activities and when lost on the seafloor. Further impacts can arise during the removal of abandoned, lost or otherwise discarded fishing gear (ALDFG). The slow growth rate of the coralligenous species suggests a reduced ability of this habitat to recover after an extensive damage. This work proposes a protocol to assess the impact of ALDFG removal on coralligenous habitat. Seven coralligenous reefs in the Capo Carbonara Marine Protected Area affected by ALDFG were compared with nearby unaffected reefs in three time-periods (before the ALDFG removal, immediately after, and one year later), applying the BACI (Before-After/Control-Impact) design. Data collection followed the STAR protocol (STAndaRdized coralligenous evaluation procedure) to apply the COARSE index (Coralligenous Assessment by Reef Scape Estimate) for the assessment of the ecological status of these habitats. Results showed a decline in ecological status only at two impact stations immediately after the ALDFG removal, followed by a recovery one year later. The intermediate layer of the coralligenous reefs was the most affected due to the loss of fast-growing species that colonized the ALDFG and were removed with them. The proposed protocol proved effective in assessing the impact of ALDFG removal on coralligenous habitat. Considering the importance of maintaining the seascape integrity, which includes the cleaning of ALDFG, this study highlights how the ALDFG removal is recommended only after careful evaluation and carried out in a manner that does not create further damage to sessile communities.