Causes of Subsea Cable Outages
Academic studies generally suggest that ships cause anywhere from a plurality to a majority of subsea cable outages. The percentage varies over time due to natural variability. The number one villain among fishing boats are the bottom trawlers. Their nets scoop up fish and shellfish on the sea floor generally in shallow waters where sea life is more abundant due to higher oxygen and nutrient levels (plankton need light). It is in the range from 100 to 200 meters below sea level that trawlers cause the most damage. Frequently the otter boards that support the nets dig deep into the sediment cutting or damaging subsea cables. See the diagram below. The general consensus is that over the last 40 years fishing's relative contribution to subsea outages has been falling. This reflects depleted open sea fisheries (fish farming has largely replaced them) as well as deeper cable burial and more emphasis on prevention. Another reason is the rise in global shipping as exports grow relative