As fish stocks decrease, fishing methods become increasingly extreme. Destructive fishing practices devastate the marine environment and include bottom trawling, bycatch, the use of poison and explosives and ghost fishing.
When fishing techniques are universally recognized as destructive, the only solution is to ban them. National legislations have identified and banned many of these practices. However, the temptation to break the law is very high both for factory ships on the hunt for huge profits and small-scale fishermen facing reduced fish stocks. Clearly, the larger and better-equipped the boats, the more devastating the impact of illegal fishing techniques is.
One of the most harmful techniques is bottom trawling, an industrial method which uses enormous nets weighed down with heavy ballast which are dragged along the sea floor, raking up or crushing everything in their way, from fish to ancient coral.
Many species, including those at risk of extinction, are accidentally caught and then thrown back into the sea, often already dead. These collateral losses, known as discards, can reach up to 80% or even 90% of the total catch.
Large areas of the seabed, the habitat where fish find food and shelter, are crushed and flattened. The biggest nets used for bottom trawling have a mouth the size of a rugby pitch and leave scars on the seabed more than 4 kilometers long. The damage caused to the ecosystem can be permanent. Bottom trawling also churns up sediment (sometimes toxic), creating turbid water inhospitable to life. This type of fishing obliterates the natural environmental features where marine animals would normally live, rest and hide.
Often used by industrial boats in the high seas, sometimes regulated in territorial waters, this practice, accused of having contributed heavily to overfishing, is a striking illustration of the lack of global fisheries management.
Seabed ecosystems are characterized by exceptional biodiversity. Over the last 25 years, scientific studies have identified very rich marine environments at depths greater than 400 meters, down to 2,000 meters and more. Despite almost complete darkness, strong pressure and very weak currents, a huge number of species can be found in these deep waters.
Living in extreme conditions, deepwater fish grow very slowly and have a long life expectancy and a late reproductive age. As a result, they are particularly vulnerable to disturbances in their environment. At-risk marine ecosystems are not only in the high seas; bottom trawling on underwater mountains and the steep continental slopes on the edge of the shelf can also cause serious damage.
The scientific community and many NGOs are calling for an international moratorium to protect the seabed from bottom trawling, but government efforts to support this have so far been minimal.
Bycatch: One of the most shocking aspects of ocean pillaging
Bycatch refers to all the forms of marine life caught unintentionally while catching other fish. Bycatch can include the wrong size of the target species, other species that are not eaten or for which there is no market and banned or endangered species such as certain birds, turtles and marine mammals. Some fish are discarded because the fishing boat is not licensed to bring them to land, because there is no space on the boat or because the captain has decided not to catch that species. The great proportion of bycatch, millions of tons each year, is thrown back into the sea dead or wounded.
A 2009 WWF report estimates that bycatch represents 40% of global marine catches, and that in many cases the fish discarded are juveniles. It is easy to grasp what dramatic consequences such devastation has on the ability of a species to reproduce and regenerate stocks.
Beyond the pressure on marine species, bycatch represents a monstrous waste of food, for both humans and marine predators. Experts emphasize that while industrial fishing boats throw millions of tons of undesired fish back in the sea each year, artisanal fishing discards are very small .
Poison and Explosives
The use of poison to kill or stun fish is very common, in both fresh and salt water, including coastal lagoons and coral reefs. Cyanide fishing, for example, is used on the now-devastated reefs of the Philippines – where an estimated 65 tons of cyanide are poured into the sea each year – and those in eastern Indonesia and other western Pacific countries.
In many places the use of poison to catch fish is a traditional technique, but negative effects have multiplied since plant-based substances were replaced by chemical poisons. These kill all the organisms in the ecosystem, including the corals forming the reef.
The use of explosives for blast fishing has also been around for centuries and is on the increase. Explosions can produce very large craters, devastating between 10 and 20 square meters of the sea floor. They kill not only the target fish, but all the other surrounding fauna and flora. In coral reefs, reconstruction of the damaged habitats can take decades.
Explosives are easily and cheaply purchased and often come from the mining or building industries. In many regions, explosives are extracted from old munitions from past wars or current conflicts. Elsewhere, fishermen buy them through illegal arms trade.
Ghost fishing is the result of nets and other fishing materials that are accidentally or intentionally abandoned in the sea. These nets continue to senselessly trap fish and shellfish and even large marine mammals, which die of exhaustion or suffocation after struggling to get to the surface to breathe. The problem of abandoned or lost equipment has been amplified by increased fishing activity and the introduction of nets and line made from long-lasting synthetic material.