Invasive poisonous fish on the rise in the Mediterranean

The predatory lionfish has already become a major threat to Atlantic reef ecosystems - now conservationists warn it's spreading in the Mediterranean. An effective way to control the fish? Put them on our plates.

A poisonous tropical fish with the potential to kill humans may be spreading in the Mediterranean, alarming conservationists who fear the creature could decimate other species in the ecosystem.

Global Ideas | 19.04.2016

The predatory, highly invasive lionfish - armed with poisonous barbs and a painful sting that can even prove deadly to humans - has been spotted in waters around Turkey and Cyprus in the eastern Mediterranean, warns the International Union for the Conservation of Nature (IUCN).

Maria del Mar Otero of the IUCN said: "The fish is spreading - and that's a cause for concern."

The species, also known as the devil firefish, is native to the South Pacific and Indian Ocean. It mysteriously reached the Atlantic some decades ago, where it has been wreaking havoc on marine ecosystems there - including in the Caribbean.

Nature and Environment | 20.02.2018

Environmentalists fear that the arrival in the eastern Mediterranean of the fish - whose stings can cause extreme pain, vomiting and respiratory paralysis - could have knock-on effects on the rest of the marine environment.

Reverberating impacts

Despite their conspicuous colors and slow movements, even sharks won't go near lionfish - meaning they have free rein to feed on and wipe out other species, including those that would normally keep algae under control.

This can attract the arrival of new invasive species, due to weakening of the local fauna and flora, said Carlos Jimenez, a marine biologist at the Cyprus Institute.

For this reason, lionfish "could have a heavy negative impact on the ecosystems as well as on local economies" in the Mediterranean said Jimenez.

The arrival of lionfish could impact local economies in the Mediterranean, as they often depend on the sea

Rise of the lionfish

The first sightings of the fish in the Mediterranean were near Israel in 1991. More recently, they have been seen in Lebanese and Tunisian waters, according to the IUCN.

The fish could have been introduced by aquarium enthusiasts who let them loose, experts say - or via the Suez Canal from the Red Sea, which can act as a channel for nonnative species.

According to the National Oceanic and Atmospheric Administration (NOAA), a US government agency, lionfish are a major threat in Atlantic reefs, and are now established along the southeast coast of the United States, the Caribbean, and in parts of the Gulf of Mexico.

Experts are still baffled as to the how the fish reached the Atlantic - but like in the Mediterranean, they believe humans lent a helping hand, and speculate that people have been dumping unwanted lionfish from home aquariums into the ocean for up to 25 years.

Cargo ships' ballast waters are also an ideal hiding place for invasive species.

The NOAA added that colder water temperatures constitute another environmental factor that controls the species' distribution on a large scale. As ocean waters warm as a result of climate change, lionfish and other invasive species may expand their range and begin affecting presently untouched ecosystems, the agency said.

Lionfish probably reached the Atlantic after being dumped as pets

Overarching problem of overfishing

But when it comes to the lionfish's spread in the Mediterranean, experts believe climate change isn't as significant as factors like overfishing.

Carl Gustaf Lundin, director of IUCN's Global Marine and Polar Program, told DW: "The Mediterranean has been severely overfished for the last 2,000 years - so climate change is the last in a long row of very bad things we have done in that sea."

Ken Collins, a marine scientist and senior research fellow at the University of Southampton, told DW that the presence of predatory grouper "controls the lionfish population in the Indian Ocean and the Australian Pacific."

But grouper "has long since dried up in the Mediterranean and the Caribbean, as they are easy to catch," Collins said.

Cumulative ocean impacts

Lundin said another factor is how marine ecosystems were already vulnerable when lionfish arrived: "Sometimes the ecosystem is disturbed, so it's not as robust as it could be."

"In the Caribbean, there should be 90 percent corals, but it's 14 percent coral now, and in some places it's even 4 percent - so that shows the ecosystem is really sick there," Lundin said.

Although the Mediterranean suffers from overfishing, catching lionfish could be beneficial

NOAA researchers warned that invasive lionfish populations will continue to grow, and cannot be eliminated using conventional methods. Marine invaders are nearly impossible to eradicate once established.

Eating for ecology

In places like Cuba, Colombia and the Bahamas, governments have encouraged their populations to start eating the fish to keep down numbers.

Cuba now holds an annual fishing tournament for the species. Restaurants have begun serving its juicy white flesh, which is enjoyed as a delicacy in Japan.

Lundin thinks encouraging people to eat lionfish around the Mediterranean would also be a good move.

"Either we do eradication, or we do control - but we can forget about eradication," he said.

In light of how overfished the Mediterranean already is, encouraging more fishing generally is not a good idea, Lundin said. "But in this case, we can make an exception."

Deep secrets of the Mediterranean

Fried egg jellyfish

With such a culinary name and its astonishing appearance, sea lovers probably do not need any further argument to be amazed. To top it off, it seems that this jellyfish's sting has very little or no effect on humans. In contrast to most jellyfish, this one can move on its own, and, surprisingly, it is one of the most common jellyfish in the Mediterranean Sea.

Deep secrets of the Mediterranean

A vast fauna down there

When you feel something unfamiliar touching your toes, it might be comforting to think it's just plants - but that's not always the case. One of the plant-like creatures living on the bottom of the sea is this yellow cluster anemone, whose polyps can have up to 36 tentacles each. In the Mediterranean, this species often appears in dense agglomerations close to sponges, tunicates and algae.

Deep secrets of the Mediterranean

Look but don't touch

Although it's very attractive for divers, this marine worm of about 15 centimeters - which can reach up to 35 centimeters - does not like to be disturbed. If so, its bristles can penetrate flesh and produce an intense irritation to the skin. Its vivid combination of colors is a warning for those in the know, but in case the message is still unclear, its name spells it out: bearded fireworm.

Deep secrets of the Mediterranean

Flying under the water

The 'wings' of the flying gurnard are, in reality, very large pectoral fins, which enable the fish to glide above the water for short distances. Disappointingly, the flying gurnard does not fly as such; it is mainly a bottom-dwelling fish and only extend its fins when troubled or in need of scaring predators. This produces a beautiful spectacle of bright and fluorescent colors.

Deep secrets of the Mediterranean

Would you guess that?

This three-centimeter flatworm is one of the enigmatic wonders that nature has to offer us. Its oval, flat body has a blue tone, a yellow central longitudinal band and dozens of white stripes - it can also appear in pink. Two tentacles on its head are reminiscent of a small mammal's ears or to a snail's horns. Its diet, sexuality and regeneration methods are also part of its unusual features.

Deep secrets of the Mediterranean

The charming, but foolish, turtles

Some of the creatures living here are far more famous - but no less outstanding. The loggerhead is the most common sea turtle in the Mediterranean - but tourism and getting caught in fishing nets mean it's endangered. Their large heads, which support powerful jaws and enable them to feed on hard-shelled prey, justify their name. But in some languages they are known as the 'foolish turtles'.

Deep secrets of the Mediterranean

'Turbot' is watching you!

Even with newly purchased professional goggles, it would be hard to notice this fish. But it is somewhere there, just under our feet. The turbot is a flat fish with both eyes on the left side of its - surely flat - head. It likes blending in with the sand and mud on the sea bed, but despite its camouflage, it is sought by fishermen around the world, as it is considered a highly-prized species.

Deep secrets of the Mediterranean

Much more than a scary presence

There are not many natural dangers in the coastal areas of the Mediterranean Sea, and that might be the reason why jellyfish create such a panic. But despite the bad rap these annoying bathing companions receive , they are actually remarkable animals. As an example, the compass jellyfish has 24 impressive tentacles and, upon maturity, it changes sexual functions from male to female.

Deep secrets of the Mediterranean

Here comes the star

The spiny starfish can reach an impressive diameter of 70 centimeters, even though the central disk is relatively small. Each of its five arms has three longitudinal rows of purple spines, each surrounded by a white cushion. Despite being native to the eastern Atlantic Ocean, its habitat range extends from Iceland to the Mediterranean Sea and the Azores.

Deep secrets of the Mediterranean

Aquatic scorpions

Not everything is peace and love under the Mediterranean Sea. The small red scorpion fish is a very venemous species due to its sharp spines coated with mucus. It is mainly found in rocky littoral habitats, even though sometimes it can be found up to 700 meters under the sea. It is carnivorous and feeds on small fish and crustaceans - of course, one would expect no less from a scorpion fish!