Falling foul of fishing by Dr Alex Rogers
While in transit from the Strait of Magellan to South Georgia, the RRS James Clark Ross ran over a long set of rope attached at the far end to a cluster of buoys, the remains of a set of static fishing gear, probably deep-water longlines but possibly from pelagic longlines or traps. This incident means that we have to divert the ship to Port Stanley in the Falkland Islands to check that none of the fouled fishing gear remains around the propellers or rudder of the ship and that they have not been damaged. Benthic longlines are set for fish such as Patagonian toothfish, Dissostichus eleginoides, in waters off the SE coast of South America, the Falkland Islands, South Georgia and elsewhere in the Southern Ocean. They comprise of lines of baited hooks weighed down to sit near the bottom and attract valuable large predatory fish.
We will arrive in Stanley during the morning of Friday 16th and a diver will inspect the propeller to make sure everything is OK, before we depart southwards again, towards South Georgia Island.
During today's navigation, we were surrounded by lots of marine birds, amongst which we saw Wandering and Black-browed Albatrosses, White Chinned, Giant and Wilson's Storm Petrels and Prions, which was a real delight!
Further information on fisheries in the high seas
After the second world war marine fisheries underwent a massive expansion and now account for a global trade worth between 80 to 90 billion US dollars per year. 2.6 billion people in developing countries rely on fish to provide more than 20% of animal protein in the diet compared to 8% in industrialized nations. Such levels of exploitation have come at a cost to the marine environment. Recent figures from the UN Food and Agricultural Organisation (FAO) show that 75% of marine fish stocks are now classed as fully exploited, overexploited, depleted or recovering. Many of the remaining 25% of stocks that are under-exploited or not exploited are low value species or those for which fishing may not be economical. These figures however, paint an overoptimistic picture of the state of marine fish stocks. Globally the trophic level of targeted fish species has declined over much of the oceans and iconic large predatory marine fish species such as tunas, sharks and billfish have declined by 90% or more in biomass over the last century with some species and stocks declining by more than 99%. In the pursuit of profit industrialized fishing nations employing sophisticated technology and powerful modern vessels have scoured the most remote parts of the oceans for new fish stocks. Fishing now takes place down to depths of 2000 m targeting species that have tremendously slow growth rates because of the small amount of energy that reaches their environment from the surface. For example, orange roughy, a deep-sea fish that frequently occurs on seamounts, may live for more than 200 years and they are unable to reproduce until they are 30-40 years old. Such species are highly vulnerable to overfishing.
As well as impacts on target fish species fishing can impact the marine environment in other ways. Removal of large predatory fish in combination with other human impacts, such as pollution, can change the structure of marine ecosystems, decreasing the value of marine goods provided by fisheries to humans but also damaging the ecosystem and affecting other services such as nutrient cycling critical for maintaining life on the Earth. Some types of mobile fishing gear, such as bottom trawls can devastate communities of delicate animals, such as corals, that have a poor ability to recover once destroyed. Even chemosynthetic communities, such as cold seeps, have been found to have been damaged by bottom trawling. Some static fishing gears can be lost and remain in the oceans fishing efficiently for years. Monofilament nets are a particular problem in this context and despite being banned globally are still in use in many regions of the world today. All sorts of debris that is deliberately or accidently discarded in the oceans can pose a threat to marine life. Plastic bags, for example, may be swallowed by turtles that mistake them for jellyfish, their natural prey. As we discovered today, such debris can pose a hazard to navigation!