Position and monitoring of anti-trawling reefs in the Cape of Trafalgar (Gulf of Cadiz, SW Spain)

Abstract

Illegal trawling was perceived in protected areas of the Gulf of Cadiz (southwest of Spain). A method of studying the nature of the seabed and identifying the paths taken by the illegal trawl ships is hereby described. So, the shape and minimum number of indispensable barriers necessary to guarantee an inoperative status for these illegal trawling vessel are defined. A new type of artificial reef is presented which is both more efficient and cost effective in terms of its construction and installation. This model has been under experimentation in the area of Cape Trafalgar, where 610 units, grouped in 11 barriers were deployed. Side-scan sonar has been used over 1.5 yrs to test the status of these barriers after their implementation. The final results of this experiment indicate that, after the first 6 mo, all illegal trawling activity had disappeared. Although the displacement of some reefs was established, these movements were not enough to reopen new trawling paths. Nevertheless, in spite of these good results, the damage to the benthic diversity is not yet resolved.