Cold-water corals in the Cap de Creus canyon, northwestern Mediterranean: spatial distribution, density and anthropogenic impact

Abstract

The occurrence and density of 3 cold-water coral (CWC) species (Madrepora oculata, Lophelia pertusa and Dendrophyllia cornigera) were investigated in the Cap de Creus canyon (north- western Mediterranean) by conducting and analysing 22 video survey transects. Species distribution patterns were also investigated at 3 spatial extents (km, 100s of m and m) across 3 of the transects using spatial statistics. Additionally, the locations of snagged benthic long-line fishing gear were logged across these 3 transects. Video surveys were carried out by both remotely operated vehicles (ROVs) and the JAGO manned submersible. CWCs were present in 15 of the 22 survey transects, pre- dominantly those covering areas with hard substrate (boulders or hardrock outcrops). M. oculata was the most abundant CWC species in the survey transects, whereas L. pertusa and D. cornigera were much more sparsely distributed, with only isolated colonies observed in the majority of transects. M. oculata showed a significant contagious distribution pattern across the analysed transects, with sev- eral scales of spatial pattern and patch size being detected, whereas L. pertusa and D. cornigera were not found in sufficient numbers to apply spatial statistics. Different covariance patterns were found across the transects between snagged fishing gear and the presence of M. oculata. Further investi- gation of this relationship and the level of hazard posed by long-line fishing to M. oculata colonies is required prior to development of a protective management strategy.