Trawling and fishing impacting underwater cultural heritage sites
Quantification of trawl damage to premodern shipwreck sites: case studies from the Aegean and Black Seas
Michael Brennan, University of Rhode Island, USA (Text)
The past four years of exploration by the E/V Nautilus off the Aegean and Black Sea coasts of Turkey have located 40 pre-modern shipwrecks, ranging from Archaic Greek to early 19th century. More importantly, these wrecks also range in their state of preservation, due in large part to the amount of damages to each site by bottom trawling activities. Analysis was conducted of the damage reflected by each wreck site, the extent and intensity of trawl scars visible in side-scan sonar mapping, and the proximity of each site to the coast and other areas of fishing restrictions. In the Black Sea, these results are correlated with evidence of anoxic events caused by internal wave activity at the oxic/anoxic interface, reflected by the preservation of wooden shipwrecks. These data show areas of the Turkish coast where sites are more severely threatened or where they may have already been eradicated. Damage reflected by the dispersal of wooden timbers or by broken ceramic cargos indicates areas that may be aided by additional establishment and enforcement of marine protected area.
The impact of the fishing trawling on the shipwrecks along the Italian coast of the North Adriatic sea
Carlo Beltrame, Università Ca' Foscari Venezia
The impact of the fishing trawling activity on the sea floor of the Italian coasts of the North Adriatic Sea is particularly devastating. It has been calculated that from the introduction of the fishing ships with engine, every square meter of the sea bottom has been covered at least three times. The impact of the fishing activity on the shipwrecks is similar to the impact of the agriculture on the land archaeological sites. The "rapido" and the "turbossofiante" are the tools used by the Adriatic fishing fleets. The first one is composed by four rectangular metal boxes with iron teeth on the bottom which are the entrance of the nets. These boxes are towed with chains and they drag on the sea floor impacting the sand for at least some centimeters deep. They are able to damage the obstacles and they are quite strong to move heavy objects for long distances.
The site of the shipwreck Mercurio, which is a brig sunk in the 1812 during the battle of Grado, lies 7 miles off the delta of the Tagliamento River 17 meters deep. It is a well preserved and coherent wreck when it was discovered in 2001, protruded from the sand with only a tumulus of concretions and some iron carronades all around it. The discovery of the site occurred thank to the "fishing" of a carronade, weighting one ton, which was recovered by one of the boxes of the rapido. Another box was lost because it got caught on another carronade. There is suspect that other carronades have been moved for some meters on the sea bottom by other fishing trawls.