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Page added on May 7, 2013
Boom in Jellyfish: Overfishing Called Into Question
Will we soon be forced to eat jellyfish? Since the beginning of the 2000s, these gelatinous creatures have invaded many of the world’s seas, like the Japan Sea, the Black Sea, the Mediterranean Sea, etc. Is it a cyclic phenomenon, caused by changes in marine currents or even global warming? Until now, the causes remained unknown. A new study conducted by IRD researchers and its partners, published in Bulletin of Marine Science, exposes overfishing as the main factor.
Jellyfish have free rein
Jellyfish predators, such as tuna and sea turtles, are disappearing due to overfishing. However, jellyfish are primarily taking advantage of the overfishing of small pelagic fish. Just like these cnidarians, sardines, herring, anchovies and more feed off zooplankton. Thus, they represent their main competition for food. In areas where too many of these fish are caught, they free up an ecological niche. Jellyfish now have free rein and can thrive. Furthermore, small fish eat the eggs and larvae of jellyfish. Therefore, under normal conditions, they regulate the population. In their absence, there is nothing to stop the proliferation of these gelatinous creatures.
Comparison as proof
In order to demonstrate the major role played by overfishing, researchers compared two ecosystems belonging to the same ocean current, the Benguela, which flows along the south of Africa. The first ecosystem is located off the coast of Namibia. Here, fish stock management measures are not very restrictive. The stocks are barely restored before fishing activities start up again. Jellyfish are currently colonising these coastal waters. The second ecosystem is located 1,000 km further south, off the coast of South Africa. Here, the opposite is true: fishing has been tightly controlled for 60 years. The jellyfish population has not increased.
Fisheries suffer the effects
A vicious circle is developing in affected areas. Under the water, the links in the food chain are much more flexible than on Earth: prey species can feed off their predators. As such, jellyfish devour larval fish. Their proliferation prevents the renewal of fishery resources. This invasive species in turn threatens fisheries. In Namibia, some 10 million tonnes of sardines in the 1960s made way for 12 million tonnes of jellyfish.
Jellyfish are the pet peeve of tourists. The sting of their poisonous filaments — although seldom deadly — is very urticant. Therefore, they put economic activities in many regions across the world at risk. This is particularly true in countries which depend on these resources, such as several developing countries.
This research work underlines the necessity of an ecosystemic approach towards the exploitation of the sea. In other words, the implementation of management measures which take into account all levels of the trophic network. According to scientists, this is the only way to prevent jellyfish from landing on our plates in the near future.
Did you know?
Jellyfish are made up of 98% water. They have neither a brain, nor a heart or teeth… And yet, they are fierce predators! They immobilise their prey with their poisonous tentacles.
The boom in jellyfish is observed across the entire planet. To date, however, there is no hard data on the increase in their global population.
There are hundreds of species of jellyfish which come in a great variety of colours, shapes and sizes, ranging from a few millimetres to several metres in diameter. The majority of them are carnivorous.
3 Comments on "Boom in Jellyfish: Overfishing Called Into Question"
BillT on Tue, 7th May 2013 1:07 pm
When will it be too dangerous to swim at the beach? Sounds like we are destroying everything we touch with our greed. After all 7,000,000,000 carnivores are loose on planet earth.
GregT on Tue, 7th May 2013 2:51 pm
The Dean of the Scripps Institute for Oceanographic Research said back in 2005, that once oceanic CO2 levels reached a tipping point, the earth’s oceans would essentially be devoid of life. All that would remain would be cyanobacteria and jellyfish. His prediction was for sometime between 2020 and 2030.
Kenz300 on Wed, 8th May 2013 12:31 pm
Around the world we have a declining fish stocks crisis, a water crisis, a food crisis, a Climate Change Crisis, a financial crisis, a JOBS crisis and an OVER POPULATION CRISIS.
Access to family planning services needs to be available to all that want it.
Worst Environmental Problem? Overpopulation, Experts Say
http://www.sciencedaily.com/releases/2009/04/090418075752.htm