Sidebar: the impact of offshore activities and fishing on underwater cultural heritage

Discussions on the environmental impact of offshore operations, as for instance, drilling for oil-wells, pipe- or cable- laying, date way back. Impact studies and mitigation have been identified as the most adequate answer to the environmental impact of offshore operations. These impact studies address the potential presence of archaeological sites and heritage of significance with the same logic as other environmental factors. Although there is certainly room for improvement, this approach works relatively well for heritage located at the bottom-surface, while deeply buried cultural heritage is difficult to detect and can only be predicted. Nevertheless, these development projects at sea and the associated impact studies have resulted in major development-led research projects and it is a great challenge for archaeologists to make the most of this development-led research, also in relation to the construction of offshore islands and the dredging for aggregates that make landfills and reclamation possible.

Fisheries are yet another matter. In contrast to offshore development projects, their impact is not negotiated on a project-to-project basis but general policies have and can be developed. In the past, the impact of fishing on the sea-bottom was not recognized as a problem. Ships engaging in seabed-impacting fishing used to be wind-propelled or had limited engine power, while larger industrial factory ships all use so-called benthic techniques, catching fish in the water column, rather than at the sea-bottom. With the increase in engine power, shallow water trawlers with ground-tackle have also upgraded their equipment to 4000 hp and even double this in more specialized instances. The severe impact of this development has made it a major concern for environmentalists. As a consequence, many countries have devised policies to ban these fisheries, or limit them to less powerful ships. The fishing techniques themselves have also changed. Ground tackle that literally ‘ploughs’ through the bottom-surface with great energy and force is being gradually out-phased in favour of tackle of a more hovering kind. The main driving force is certainly to economise on fuel, but the reduction of impact on the sea-bottom is a welcome side effect.


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The impact of fishing on underwater cultural heritage


Concern about fisheries

So far, concern about the impact of fisheries has focused on the ecosystem and neglected the underwater cultural heritage as illustrated by the UN General Assembly Resolution 61/105 of 8 December 2006 on sustainable fisheries.

The discussion on the impact of fisheries in the context of underwater cultural heritage has, however, begun. This crucial debate is marked by assumptions.  Moreover, it is often diverted, leading at times even to a misuse of the threats posed by fisheries as an excuse for even more destructive activities. These complications are not very helpful for putting the real impact of fisheries into perspective.

Fishing techniques' impact

Large scale industrial fishing techniques are benthic and do not affect Large-scale industrial fishing techniques are benthic and do not affect underwater cultural heritage. Stationary fishing techniques are not very intrusive either. It is, however, undeniable that fisheries using ground tackle have an impact on the sea-bed, all bottom life and by extension on those archaeological phenomena that occur right at the sea-bottom surface. Apart from the side effect of important discoveries through trawlers catching artefacts in their nets or by losing their nets after collision with a site, ground tackle has had effects on archaeological sites that have become ever more detrimental with increased engine power.

Litter deriving from fishing has systematically affected the bottom of large tracts of shallow seas and the heritage located there. Lost fish tackle, including hooks and small anchors, dating from all periods subsequent to the first formation of the site, are a standard feature of all archaeological sites at sea. Today’s durable synthetic netting materials, which are not necessarily a sign of trawling, litter the sea bottom and tend to collect especially around surface irregularities such as archaeological sites at the bottom surface.

Most fisheries however, no longer use ground tackle at all. And for those that do, destroying archaeological sites is not the result of responsible and informed economic practice but rather due to negligence or bad information. Responsible local fishermen with detailed knowledge of sea bottom conditions try to avoid direct contact with sites that destroy their equipment as ground-tackle gear is expensive and sustains their livelihood. These fishermen will map with utmost accuracy anomalous bottom features such as archaeological sites or offshore installations but nonetheless trawl as closely to them as possible because they feature a different and richer marine life than elsewhere. Fishermen using more stationary non-intrusive tackle will even more purposefully seek out hotspots of stationary fish and bottom crawlers.


Situations negatively impacting archaeological sites can be avoided through mutual dialogue and information. It is vital to consider fishermen as natural allies in heritage protection. Fishermen’s interests are not – in principle – at odds with heritage protection. With their local knowledge they can be important informers on changing marine conditions and on discoveries of heritage. If sites are subject to a management plan, one should consider what fishing techniques, if any, one would want to allow on-site. Many techniques, however, are more harmful in combination with other uses, such as recreational diving, or functioning as a breeding ground for specific species, than they are for the physical properties of a site as such.

Allies in the management of underwater cultural heritage

In many countries, fishermen are already important allies in the management of underwater cultural heritage. They are invited to share their information with the competent national authorities and thus contribute to the establishment of inventories. Archaeologists benefit from consulting them as much as possible, both on the general conditions of the marine environment and on the whereabouts of irregular features at the bottom surface. Conversely, they should inform them about areas that should be avoided, in order to prevent endangering submerged archaeological sites. If fishermen act as bad partners in heritage management, this is often due to negligence in communication with them. It is the responsibility of those who care for heritage to make sure that fishermen are well-informed and conscious of the importance of heritage protection. It is vital for all stakeholders to establish a mutual understanding between heritage managers and the fishing industry.

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