What future for fish?
Fish in a wine glass
© International Polar Foundation
On their way from the Mediterranean Sea to the Spitzberg, the crew of the Alcyon meet fishing boats of all types and sizes, from the smallest fishing boat to the big trawler. For many people, fishing is a nice afternoon, lazily spent by a lake or a riverside. But fishing, with all its linked activities, is, above all, the profession of 200 million people throughout the world! And all these lives depend on fish's future.
Marine environments are often vulnerable and the human influences might break, in some cases, a fragile balance that will be very hard to restore afterwards. It is therefore a crucial question for many people: at present time, with our scientific knowledge, can we predict fishes' future?
Back in 1946...
In 1946 already, the question of overexploitation of marine resources was mentioned for the North Sea during an international conference in London.
The practice of an intensive fishing really began after the Second World War, especially in the North Atlantic. From then on, with all the technological progresses (sonar, synthetic fibres, on-board freezing, etc.) fishing quantities always kept increasing. Boats got bigger and bigger, going always further and fishing always deeper. The "factory ships" outreached everything: these boats stay at sea nearly all the time, and all the necessary supplies and exchanges pass through other boats that come to meet them.
Another extreme fishing practice is trawling. These boats drag an enormous net, which rakes the bottom of the sea. In the Gulf of Gascogne, for instance, every square meter is "scraped" six times per year!
When consequences began to show
Different species of fish reproduce at different speed. Some get more offsprings at once than others. Anyhow, if fishermen catch fishes faster than they can reproduce, this specie will slowly disappear. This phenomenon is called "over fishing".
Back in the 70s, some areas already observed a serious depletion of certain species: the anchovy in Peru, and the cod in the North Atlantic. Things only got worst, as the number of fishing boats kept increasing. From then on, politics tried to set up laws for fishing practices.
Fishing is not the only cause
In the 70s, while these legal controls were being set up, scientists tried to understand what was happening.
Most fishes live near the coasts because their food concentrates, mostly, in shallow waters. Human activities also concentrate in coastal areas, having therefore great impacts on the environments where these fishes live.
Progressively, three main causes have been identified:
- The over fishing (which is the first cause of fish stock depletion)
- Coastal planning (which modifies the living environment of fishes)
- Pollution (80 % of the marine pollution comes from the continents!)
More than 30 years after the first awakenings, we are still discovering new impacts of human activities on the marine environment and, therefore, on fishing:
"Dead zones"
For instance, in 2004 the UN published a report revealing that there were 146 zones throughout the oceans of the planet that are, at least seasonally, totally devoid of oxygen. They result of an excess of nutriment in the water (mainly nitrogen, coming from agriculture, car and industrial pollution, and wastes).
The excess of nutriment causes tiny marine organisms (called phytoplankton) to multiply.
When they die, their decomposition will absorb great quantities of the oxygen contained in the water. This phenomenon is called "eutrophication". Fish flee these suffocating zones. Other animals, that cannot move quickly enough or cannot move at all, dye (clam, crayfish, oyster, etc.).
The number and the size of these zones are increasing since the 60s. Some reach the size of 70 000 square kilometres! The biggest of these zones are found in the Gulf of Mexico (which collects the waters of the Mississippi river), in the Baltic Sea, in the Black Sea, in some Scandinavian fjords, but also in China, Japan, South America and Australia...
The UN report concludes that these " dead zones " threaten the fish stocks and the human population depending upon them.
The water of the Gulf of Gascogne warms up
Just a few weeks ago, a study was published by IFREMER (the French Institute of Research for the Sea Exploitation) raising our awareness to a new phenomenon: the water warms up!
They measured that the water of the Gulf of Gascogne warmed up of a mean 1.5°C since 1970, near the surface; and of 0.8°C at a depth of 200 meters!
Of course, fish reacts to these changes, but not necessarily in a bad way: different species of fish (that like warmer waters) will simply become more abundant. Unfortunately for fishermen, it seems that these are not always the best ones to eat!
Fishes' future
Some species are already extinct. But in spite of this gloomy situation, nothing is decided yet. The future of the remaining species will depend on the concrete actions that men will set up to protect them.
Conventions and Codes of Practice already exist since many years. Even if their application is not always easy, their use by a majority of the world's countries would be a fantastic progress.
Local initiatives do take place. For example, the countries bordering the Rhine river committed themselves to diminish their nitrogen production (one of the causes of eutrophication and "dead zones") by half, and, in that way, lowered the amount of nitrogen going into the North Sea of 37 %! Let's hope such initiatives will be more and more numerous!
And finally, it would be wise to encourage preliminary studies before any public works on the coast, which would avoid some quite stupid mistakes:
To allow an easier access for windsurfers, a section of the coral reef of an island of the Caribbean was blowed up. This modified the local marine currents in such a way that all the sand of the beach was removed, which not only seriously compromised the touristic activity of the island, but also caused the erosion of the island's coastline! Of course, the fish that used to be protected by the reef disappeared when waves and strong currents invaded the lagoon.
