Fishing vessels share the waters around the UK with the oil and gas industry. This has led to interaction in the past, with several instances of fishing vessels colliding with surface installations, and snagging their gear on subsea equipment. This latter risk in particular has resulted in tragic consequences, and is the main focus of this discussion.

To assess the risk of fishing vessel interaction with subsea equipment, information is firstly required about the fishing intensity within the area of interest. In general, no single data source is sufficient for this task, and Anatec studies combine data from several sources, including AIS, Government statistics, surveillance data, survey data and liaison with local fishermen’s organisations.

AIS is now the most accurate method of tracking fishing vessel activity in offshore areas in the EU, as it is mandatory for fishing vessels of 15m length and over to broadcast their position, normally several times per minute. Anatec has a unique, comprehensive database of fishing vessel activity in UK waters and reliable data for many other regions. 

Once the fishing activity data has been collected, assessment work may be performed to quantify the level of risk. The frequency of interaction may be estimated based on the fishing effort, types and sizes of gear used and seabed structure dimensions. The consequences, which could range from initial impact, pull-over load and snag load, will depend on the vessel size and power, fishing method (warp arrangement, gear mass, speed, safety devices, etc.), crossing angle and design of the seabed structure.

Experience gained from the risk assessment should allow appropriate risk mitigation measures to be identified, for example, trenching or burying pipelines, surveying for spans and designing manifolds and wellheads to be over-trawlable.

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