What are some natural shark repellants
Great White Shark: Danger or Endangered?
Summary of White shark continues to pose many puzzles to science. Age and sexual maturity of the animals are just as unknown as their routes through the Oceans. Thanks to modern technology, such as satellite-based long-term transmitters, two puzzles could soon be solved: Where does the great white shark go when it leaves the coastal regions? And: How many animals are there exactly? These findings could help to protect the endangered animals - provided that humans accept the large predators off their coasts.
An encounter with a great white shark in the wild is - different. At first glance, he doesn't look like the wild beast you know from the media. He looks rather stout, not to say: fat. When he opens his mouth, soft bulges wobble on his cheeks - a fat, slightly stupid grin. Viewed from the side, one of the most feared predators in the world resembles a chubby buffoon.
This impression changes suddenly when the supposed clown turns to us. Suddenly we understand the fear, even panic, that this animal triggers in most people, and feel it firsthand. Seen from the front, the head looks like a pointed wedge with black eyes that fix us darkly. The sagging jaws and grins are gone. The only thing we notice at this moment are the multi-row, five centimeter long teeth.
The shark approaches slowly and confidently, turning its head first to one side and then to the other, seems to be wondering whether we are worth its time. If we're lucky, he turns away, becomes a clown again and disappears into the twilight.
Biologists distinguish between more than 500 species of shark, but the human imagination is really only concerned with one species: the great white. A good 40 years after Spielberg's “Jaws” ruined the beach vacation for an entire generation, the predatory fish is still one of the greatest movie stars of all. In the globally successful animated film "Finding Nemo", the second part of which will be released this fall, the role of the villain was neither cast with the aggressive bull shark nor with the tiger shark, which would fit much better into the coral reef setting. Instead, of course, the great white shark was once again seen with a snarling grin on movie posters and in film trailers.
Every toddler recognizes the great white shark, and yet we know little about him. Nobody has ever seen the predatory fish mate or give birth to young. Nobody knows when they will reach sexual maturity or how old they will be. We don't even know which routes they follow through the oceans or how many there are.
NG Video: How Brian Skerry Photographed Cape Cod's Great White Sharks
And what little we think we know is often wrong. The great white shark is not a merciless beast that tears up its prey in a bloodlust, but is surprisingly careful when attacking and is probably smarter than many experts had assumed. People fear the sea hunter not only because he is six meters tall and bites with a pressure of two tons, but because it is a maritime phantom. Because we know so little about animals, we feel insecure, disoriented and threatened. But the more we know about that Carcharodon carcharias find out, the better we can assess whether it represents a danger to people - or whether they have to be protected from people - fishing fleets, environmental pollution, sport fishing.
Should we fear the great white shark, the most famous killer on the planet - or should we feel sorry for him?
The great white shark makes it difficult for scientists to find answers to these questions. If there were a dangerous land predator hunting its prey along the coasts of California, South Africa or Australia, researchers would have long since carefully examined its mating habits, migration and behavior. In the ocean, however, different rules apply. Great white sharks appear and disappear, in deeper ocean regions it is almost impossible to keep track of them. The fish cannot be kept in saltwater aquariums, as they put themselves in danger or attack other tank inhabitants in captivity. Some sharks went on hunger strikes or kept ramming their heads against the wall. Several operators of seawater aquariums have had to release captured great white sharks.
Despite these difficulties, thanks to modern technology, scientists are on the verge of unraveling at least two of the great white shark's secrets. Which marine region does he retreat to when he leaves the coasts behind? And: How many animals are there exactly?
A beautiful summer afternoon on Cape Cod on the Atlantic coast of the US state of Massachusetts. There is a seven-meter fishing boat near the beach. The passengers - biologists, tourists, journalists - have made themselves comfortable on benches. Over the radio they listen to a pilot circling 300 meters above them. In a distinctive New England accent he says: "A damn pretty shark swims a little south."
The fisheries biologist Greg Skomal, who works in the Ministry of Energy and Environment, perks up and climbs onto a porch at the bow that protrudes over the railing by one and a half meters. However, he is not holding a harpoon or fishing rod in his hand, but a three-meter-long pole with a video camera. When the captain finally accelerates, Skomal grins in anticipation like a small child.
For a long time, the researcher had little opportunity to study the great white shark. On the east coast of the USA, the animals appeared very rarely - every now and then one got caught in a fishing net. But the east coast was not counted among the marine regions where great white sharks gather in greater numbers and hunt seals at certain times of the year: the Pacific coast off California and Mexico, the southern coasts of South Africa and Australia. When a single female swam through the shallow bays and inlets of Massachusetts for a long time in 2004, Skomal, who has been studying the fish with tracking devices for 20 years, was electrified: a great white! Right on the doorstep! “I just thought: What luck! I'll never get a chance like this again! ”He says. He stayed on the trail of the female shark for two weeks, christened her “Gretel” and shot an electronic tracking device under her skin with a small harpoon.
However, the station fell off after only 45 minutes. Skomal's chance to finally learn more about the mysterious migratory movements of the great white sharks was gone for the time being. Five years later, on the first Sunday of September 2009, a pilot spotted five great white sharks off Cape Cod. By the time the weekend was over, Skomal had tagged them all. “I totally freaked out,” he says. “The adrenaline lashed through my veins. That's what I've always dreamed of. ”By now, Skomal may have gotten used to it. Because the sharks have been visiting the US east coast every summer since then.
California has more experience with animals. Scot Anderson has been observing the sharks off the Californian coast since the mid-1980s - initially the researchers followed the fish with the naked eye, later they used acoustic tracking transmitters and now state-of-the-art satellite technology. Over the past 30 years, Anderson and colleagues have documented thousands of shark sightings. The experts identify individual animals based on the shape and drawing of their caudal fins or describe the line between the gray body and the white belly. Today, at least for the marine region off California, biologists can say how many sharks there are and where they can be found.
To determine the total population, the biologists use a statistical formula based on the so-called catch-recapture method. To do this, the number of sharks that are sighted in an area in a certain period of time is compared to the individuals who have already been sighted there before and to those who appear for the first time, and thus conclusions about the total population are obtained.
In 2011, a team of researchers calculated using this method that only 219 adult great white sharks live off California. The low result shocked experts and the public alike - and soon came under fire. Another team of researchers reevaluated the data but made different assumptions and estimated the number of sharks for the marine region to be more than 2000 (including the juveniles that were not included in the first calculation).
A little later, a working group in South Africa estimated the population there at around 900 animals. Another 120 specimens live off the Mexican island of Guadalupe. The interpretation of the shark census is difficult: how are these numbers to be assessed? And when is a population considered stable?
The international environmental organization IUCN describes the great white shark as an "endangered species". This classification sounds understandable if one follows the highest estimates, which assume a global population of 25,000 animals. According to the lowest estimates, however, there are only about 4,000 great white sharks in the world - as many as wild tigers that are officially "critically endangered". The Australian statistician and shark expert Aaron MacNeil sees reason for cautious optimism - also because of the regular shark sightings off Cape Cod. “Historically, there are fewer great white sharks today than in the past,” says MacNeil, “but the species is not critically endangered. Presumably their number is even increasing very slowly at the moment. "
A positive development is that, unlike related species, great white sharks are rarely hunted by commercial fishermen. Sport fishermen hungry for trophies and trawls in which the great whites end up as bycatch continue to threaten the species. Since the great white shark is at the top of the food chain, it plays an important role in the ecological balance of the oceans.
To clarify whether the great white shark is a species in need of protection, it is important to find out more about its migration routes. Unfortunately, sharks move less predictably than migratory birds: Instead of moving from region A to region B at a certain time of the year, the sharks behave erratically: some stay on the coast, others zigzag hundreds of kilometers through the open sea. Many sharks - but not all - seem to migrate between warm and cold water depending on the season. And males, females and young animals are on different routes.
For some time now, satellite-based long-term broadcasters have been providing research with informative information. It is known that adult great white sharks leave the coasts of California and Mexico in late autumn and move to the deeper ocean regions in the middle of the Pacific, which some marine biologists call the "desert of the ocean". “What on earth are they doing there?” Asks the Californian shark researcher Salvador Jorgensen. He suspects that the sharks reproduce there, which would also explain why a diver or submarine has never observed a shark mating. The "desert of the ocean" is huge, the water several thousand meters deep. The analysis of the satellite data showed that females move straight into the area, while the males migrate back and forth between different sea depths - looking for mates?
Later, the males swim back to the coast while the females stay on the high seas for another year, possibly to give birth to their offspring in an unknown location. What is certain is that the young animals will appear at some point in the feeding areas of the middle latitudes, where they will eat fish until they are big enough to go seal hunts further north and south with their conspecifics.
The puzzle is far from complete. It is still unclear where the boys will be born. And so far only the population off California has been examined in more detail. Australian sharks are believed to swim along the south coast in search of food, but it doesn't look like there are any particular migratory movements or mating encounter there. Even less is known about the conditions in the Atlantic. Greg Skomal says, “There are hikers and there are coastal residents. But I have no idea what it is based on. "
What he does know is that the great white shark has a long history on the US east coast. In his study in New Bedford, he shows documents that prove that the indigenous people were already seal hunting. Analysis of bones found at archaeological sites suggests that the seal populations in what is now New England collapsed as early as the 17th century - and that is why the sharks stayed away. Only recently have there been larger seal colonies in the region thanks to strict nature conservation laws. And the sharks came back with the prey.
On a patrol flight over the east coast, Wayne Davis, an experienced pilot who helps marine biologists track down great white sharks, spots seven of them in just 30 minutes of flight. The fish swim in front of beaches where seals forage for food. The beach is only one and a half kilometers away. The people of New England have so far accepted the newcomers. There are t-shirts and posters for sale, on which the sharks are mostly shown from the side - as happy pranksters. But experts assume that somebody will get to know the sharks from another side at some point - and face a shark and its countless teeth head-on.
It is true that shark attacks on humans are very rare. According to a new study by Stanford University, one shark attack comes to 738 million beach visits. The last fatal shark attack off New England occurred in 1936. In 2012, a swimmer was bitten in both legs, and in 2014, two canoeists were thrown from their canoes and escaped in terror. How long does happiness last?
At the latest when another person is killed by a great white shark off Massachusetts, in the Mediterranean or in the South Atlantic, it becomes clear where we really stand: Can we overcome our fears and give the great white shark - the legendary killer, the clown with the black eyes - one Give a Chance?
(NG, issue 7/2016, page (s) 96 to 119)
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