The world’s oceans are changing. Fishing and hunting have emptied the seas of many of its largest marine mammals, sharks and turtles. Warming waters are causing corals to bleach, and rising levels of carbon dioxide are turning our seas more acidic. If you were to ask what is responsible for these changes? And what can be done to reverse them? You might be surprised by the answer.
Dr James Barrett has a rather unusual job. He, along with his fellow archaeologists from the University of York, compile records of the fish bones and other food items found at archaeological dig sites. They discovered that fish bones from the earliest sites (around 600 AD) were composed solely of freshwater species taken from rivers and lakes. Species such as salmon, trout and eels. However, at around 1050 AD, they observed a sudden and dramatic shift to occur in the types of fish people were eating. Bones from herring, haddock, cod, and other species that spend their entire lives at sea suddenly started to appear in the record. By the 15th century, marine fish made up 60-80% of all fish bones found in archaeological deposits. So, why the sudden shift from land to sea? Research by Professor Callum Roberts suggests that technology lies at the root of our maritime revolution.
Before the plough, irrigation and other forms of modern agriculture, the forests were largely intact. Tree roots anchored the soil in place, and streams and estuaries ran clear. Migratory species like salmon, eels and sturgeon ran through these waters in their hundreds and thousands in order to reach important spawning and feeding grounds. However, the rise of agriculture caused many forests to be cleared, meaning soil was free to wash into streams and lakes. People also began damming streams and rivers to farm fish in man-made ponds, and draining marshlands to create new agricultural land. By the end of the 11th century, dams, weirs and water mills had been constructed across almost every watercourse in Britain. With growing human populations came increased levels of pollution and sewage, along with toxic effluents from tanneries, dying works and mines. Not only did all these developments block the routes of migratory fish, they also clogged our rivers and streams with silt causing freshwater fish to experience widespread declines. Consequently, fishermen throughout this time increasingly began to look to the sea as a means to boost dwindling catches.
By weaving natural fibres, fishermen have been using nets to catch herring, mackerel and other species that shoal close to shore for over a thousand years. However, between the 8th and 11th centuries, Viking invasions introduced Europeans to new technologies such as hooks and lines. This allowed for deeper water fish like cod, ling and haddock to appear on people’s plates for the first time. Further advancements were made in the late 1300s after sail vessels began towing large trawl nets across the seafloor, capable of catching huge quantities of flatfish and whitefish. The 18th century then saw some fishermen abandoning their single hand lines in favour of longlines armed with hundreds of baited barbs. Then, in 1870, the world’s first steam-powered trawler was launched. Much to the anger of those around them, these vessels did not have to wait for wind or tide, giving these new vessels the upper hand. Finally, in 1891, the invention of the diesel engine changed the world forever. Vessels could now sail further and for longer than ever before, pushing into new virgin fishing grounds. Fishermen on such vessels were rewarded with catches so large that they could stop the boat in its tracks, or even tear its nets.
Fast forward to the present day, and hydraulic winches are towing nets the size of football fields and hauling catches weighing hundreds of tonnes. Acoustic fish finders allow fishermen to target aggregations of fish with ever increasing accuracy. And some fishing gears are even able to electrocute and catch their stunned prey. All of these technological advancements have proven great at removing incredible biomasses of fish and other animals from the oceans, causing marine ecosystems to undergo dramatic changes that will persist for hundreds of years. Then again, fishing is just one of the many impacts technology is having on our seas.
It is widely agreed that our dependence on fossil fuels is causing carbon dioxide levels to rise at an unprecedented rate, trapping heat in the Earth’s lower atmosphere. As a result, the oceans are warming, causing corals to expel the photosynthetic algae contained within their cells (often leading to their death) and forcing many species to shift polewards. The oceans mop up some of our surplus carbon dioxide, making them more acidic in the process. Many scientists fear this will reduce the amount of carbonate available for plankton, molluscs, corals and crustaceans to form their protective skeletons, which would generate severe knock-on effects for food chains across the planet. Meanwhile, the widespread use of plastics combined with our throw-away culture and means even the deepest abyssal plains are now smothered in litter. Then again, although technology is clearly playing a key role in deteriorating of our oceans, some believe that technology could also help us pave the way for healthier, more sustainable seas.
In a world ruled by stock markets, photocopiers and café lattes, it’s easy to see why many consider the life of a fishermen to be romantic and free. However, fishermen’s lives are restricted by as much red tape as any overly bureaucratic office. Attaining a fishing license often comes with strict rules. Rules on the types of fishing gears you can use, the hours and days you can fish, what species you can catch, and how many you can keep. With the costs of operating a vessel ever-increasing, and the most regulated species reaching incredibly high values (a single blue fin tuna recently sold for a record $1.76 million), many fishermen fall to temptation and break the rules. Illegal and unreported fishing is estimated to remove 11 to 26 million tonnes of fish from the sea every year. Weighing more than the entire human population of the United States, this criminal activity is thought to be worth between $10 and $23.5 million yearly. However, technologists may have found a solution. Automatic Identification Systems (AIS) are installed on most ships greater than 15 metres in length. By electronically tagging and identifying vessels, AIS technology is primarily used to help captains avoid colliding with other ships. Now, projects such as Global Fishing Watch and Eyes on the Sea intend to use this satellite data for a very different purpose; to monitor where people are fishing. The new technology can help flag suspicious behaviours, such as fishermen turning off their AIS and turning it back on many miles later. The teams involved could then provide this information to port officials to help them decide whether to inspect the ship, bar it from entering, or even take legal action.
And it’s not just illegal fishing. Boats that fish within the confines of the law also generate environmental problems. Most fisheries generate some form of by-catch. That is, they accidentally catch fish that the fishermen either do not want, or are not allowed to keep. For instance, for every 1 kg of prawns generated by trawlers, anywhere between 9 and 20 kg of other species are captured. As most by-catch is discarded back to the sea dead or dying, it represents a colossal waste in resources. Whilst fishermen cannot choose which fish enter their nets, new technologies may allow unwanted species to escape capture before the nets are hauled on deck. Dan Watson, the young British creator of SafetyNet, sees ocean bycatch as more of a design challenge, rather than an inevitability. By fitting nets with flashing LED rings, he believes fish will view the lights as exit signs, allowing small fish to make their escape through the rings whilst keeping the larger ones in. Fishermen wouldn’t need to think about changing the batteries, or even switching them on and off, as the rings harvest their own energy from the nets’ motion and the lights are only activated at certain depths. Furthermore, as the rings are rigid, they keep the surrounding net meshes open, preventing the gaps from closing when the net is under heavy load – fish are often injured in traditional nets when this happens.
Technologists are also looking to remedy more than just the impacts of fishing. A Dutch Company is using 3D printing technology to create their own coral reefs. Taking 13 hours to print and built from real sand, these reefs have been specially designed by scientists to enhance colonisation by corals and other tropical species. On a similar vein, frames made of Biorock or Seament can be made into any shape. Passing an electrical current through the structure attracts carbonates, the same chalky skeleton that form the back bone of coral reefs. As a result, these frames prove exceptional at attracting settling corals and other species. Floating garbage collectors that can passively remove hundreds of kilograms of plastic from the oceans each day are to trialled for the first time this year, and could help control the rising levels of plastic in our seas. And fish farms that, in addition to fish, also cultivate filter-feeding organisms such as mussels, scallops, sea cucumbers and kelp. Not only can this increase the profits of the fish farm, but these organisms can directly feed on the farm’s effluent and toxic secretions, purifying surrounding waters.
Although these technological developments are a step in the right direction, many fail to tackle the root of the problem. Plastics will continue to be dumped into the sea, fishermen will still take catches illegally, and carbon dioxide levels will continue to increase. Then again, there is no cure-all solution. Meaning that, if we employ them together, these new technologies could indeed help pave the way for healthier, more sustainable seas.