Trends and Developments of Trawling Capabilities and How They Relate to the Design Load Regulations for Subsea Structures

Master's thesis in Offshore Technology : Subsea technologyEver since oil has been extracted on the Norwegian continental shelf, fishing activities and oil and gas retrieval has had to coexist. One of the interactions between fishers and that can be hard to avoid are the interactions between bottom trawling and subsea installations. This thesis has researched regulations relevant to the overtrawling of subsea structures and pipelines, as well as previous research relevant to these. Interviews were done with experts on trawl fishing from both the authorities and the two aforementioned industries. The answers were used as theory background help, as well as for the analysis. A data set was compiled of ships that are currently in use or were very recently in use for trawling, with a focus on bottom trawling. The collected data set was then used in a data analysis and plotting process to identify trends and developments in the fishing industry, particularly regarding the dimensions of vessels and their gear in relation to their build year. Expert opinions and data analysis partly coincide, where it was seen that developments were heading towards larger ships and larger fishing gear. Future research was recommended by the extension of the ship data set, AIS data evaluation and trawl tests on subsea structures. It was concluded that for regulations on subsea structures to be up to date and at a level of the existing regulations for subsea pipelines, modern ship and gear capabilities have to be researched and used in the development of new tests to keep up with trends in the industry