What happened to the USS Indianapolis
Ocean whitefin shark: the last of its kind?
Summary: They were considered the most common type of shark in the open sea, ruled the oceans and the nightmares of seafarers: the deep-sea white fin sharks. Today the two to four meter long fish often end up as bycatch on longlines or perish in trawls. Nevertheless, neither conservationists nor the public are interested in the animals that are threatened with extinction. It is questionable whether recent protective measures such as fishing bans can prevent the sinking of the great sea predators.
“What we were allowed to see then will probably never happen again. At least not in our lifetime. Maybe our offspring will be lucky, but I don't think so. ”With these words, diver Valerie Taylor reports on an encounter with a school of deep-sea white-fin sharks.
The drama took place during the making of the documentary "Blue Water, White Death," which was released in 1971. The film was sensational for two reasons: On the one hand, the divers filmed the animals for the first time outside of protective shark cages 150 kilometers off the South African coast. On the other hand, a whale carcass attracted so many sharks "that they could no longer be counted," as Taylor reports.
The film scene is the oceanic counterpart to the few black-and-white photos from the 19th century that show huge herds of buffalo roaming the North American prairie. The last great appearance of a species. A natural history document. Deep-sea white-fin sharks (also known as white-tip deep-sea sharks) were once the most common type of shark in the open sea. Today the animals are rarely seen. White-fin sharks, which can grow to be two to four meters long, often end up as unwanted bycatch on longlines or perish in trawls.
A 2004 study by marine ecologist Julia Baum found that the population in the Gulf of Mexico has shrunk within 50 years. Other studies show similarly dramatic declines in the Atlantic and Pacific. Given such numbers, it is amazing that neither conservationists nor the public are facing extinction from Carcharhinus longimanus pay close attention so far. One of the few researchers interested in the white fin shark is Demian Chapman of Stony Brook University in New York State. He says: "When I talk about the animal, people often have no idea what I'm talking about."
And whoever has heard of the rare predatory fish is mostly afraid of it.
In the middle of the last century, the diving pioneer Jacques Cousteau once described the deep-sea white fin shark as “the most dangerous of all sharks”. The bad image of the species was also cultivated in the horror film "Jaws". In a famous monologue, the experienced captain Quint, who is supposed to hunt down the sea monster, tells how he survived the sinking of the US warship “USS Indianapolis” in World War II: “1,100 men went into the water, 316 were rescued, the rest was for the sharks. "
The film scene is a mixture of historical reality and fiction: Of the almost 1200 men on the "Indianapolis", only 317 were actually rescued. It is also true that large numbers of sharks were sighted back then, most of which were probably white-fin sharks. If you talk to survivors like the now 92-year-old Texan Cleatus Lebow, who was rescued after a long five days in the sea, you don't get the impression that the sharks were his biggest problem at the time: “The worst thing was thirst. I would have given anything for a cup of fresh water. ”And the sharks? “Sometimes they swam around us. But they left us alone. ”Lyle Umenhoffer, who was the same age and died in autumn 2015, had similar experiences:“ You had to be on your guard when sharks were around. If they got too close, we kicked them. But I wasn't afraid of them. We had other worries. "
In order to be able to classify the stories of contemporary witnesses, one must take into account that the survivors of the doom were spread over an area of more than 250 square kilometers and therefore experienced very different things (and a man who is killed by a shark can too do not tell about the fact that sharks are actually quite harmless).
But when 14 of the 31 surviving soldiers of the "USS Indianapolis" met in the summer of 2015, none of them described the sharks as the greatest danger. In a sense, however, the film captain Quint was right when he said "the rest was for the sharks".
White-fin sharks also eat carrion and have certainly not spurned the almost 1,000 human corpses. Detailed analysis of the reports is important if one is to refute the image of the white fin shark as a voracious killer and to save the species. But it may be too late for that. Because if a large ship were to sink today and thousands of people would be floating in the sea, they would only see a few sharks. That might sound reassuring, but it's not good news.
What happens on land when dominant predators disappear is well known: a biological chaos arises. The decline of species at the top of the food chain, according to a report that was published in 2011 in the specialist magazine “Science”, “is probably the most pervasive human intervention in nature”. In parts of Africa, for example, dwindling lion and leopard populations have resulted in baboons multiplying uncontrollably - and with them their dangerous intestinal parasites, which are now increasingly affecting humans. In the "Science" article, the scientists warn of pandemics that could spread in this way. White-fin sharks play a role in marine ecosystems similar to that of the big cats of prey on land. What changes there when they become extinct? We have no idea. Zero.
The disappearance of the sharks is possibly more dangerous for humans than the predators themselves. Valerie Taylor had experiences similar to those of the survivors of the “Indianapolis” during the filming of “Blue Water, White Death”: White-fin sharks are not shy; when you approach people, you bump into them. As long as the divers stay in the group and keep their hands and feet at a distance, they usually do not attack seriously. “The sharks examined us closely,” says Taylor. "At some point they must have come to the conclusion that we were not worth the effort and disappeared."
But that does not mean that the white fin shark does not pose a threat to humans. After all, the high seas are an ecological wasteland, the sharks rarely encounter potential prey here, which is why they waste neither time nor energy when they finally have a delicacy in front of their huge mouths. If you discover a school of tuna, a dead whale or a group of castaways, swim there immediately to check the opportunity. So if a diver is the only protein supplier within a hundred nautical miles, the white fin shark becomes a potentially dangerous attacker. Otherwise, it will only scare you.
Few researchers have been lucky enough to see deep-sea white fin sharks hunting. When fishery biologists examined the stomach contents of some predatory fish in the Gulf of Mexico in the mid-20th century, they found, to their surprise, tuna weighing five to nine pounds. The sharks are actually much too slow to hunt small tuna. One day the researchers observed a group of sharks swimming through a school of tuna with their mouths wide open. "The sharks did not try to hunt them or to snatch at them," reported the scientists, "they just waited for a fish to swim in their mouths."
It is not without irony that the researchers who documented the spectacle contributed indirectly to the fact that we can no longer experience something like this today and that the shark population declined sharply in the following decades. “The researchers wanted to find out which forms of fishing would be profitable in American waters,” says California marine ecologist Julia Baum. “It was for this purpose that longlines were laid out for catching tuna at the time,” explains Baum. The predatory fish ate the tuna that were already hanging on the hook and were then caught themselves. Baum says: "There were so many sharks that one had to doubt whether commercial tuna fishing would even be possible."
The fishermen were not discouraged and found two solutions to the problem: On the one hand, they shot sharks before they could eat the tuna on the hook. On the other hand, they laid out their own lines for shark fishing because they soon realized that a lot of money can be made by selling shark fins in Asia.
These methods and factors are responsible for the decline of all shark species - but the white fin sharks have been particularly hard hit. In 2010, the five largest international fisheries associations that control sword and tuna fishing completely banned their vessels from catching white fin sharks. No other shark species has so far enjoyed similar protection. The Washington Convention on Endangered Species also enacted rules in 2013 that are intended to make the legal trade in shark fins even more difficult.
It remains to be seen whether these protective measures are sufficient or whether they are already too late. There are fish species that recover quickly from temporary overfishing because the individuals quickly reach sexual maturity and the females produce many thousands of eggs. Most shark species, on the other hand, are only able to reproduce when they are a few years old and only give birth to a few young every one or two years. In the case of the high seas whitefinned sharks, "we're not even sure whether they reproduce every year or less," says marine biologist Edd Brooks. Even if strict environmental protection rules are introduced, the population therefore takes a very long time to recover from overfishing.
Edd Brooks is part of a research team at Stony Brook University that has been providing white-fin sharks with tracking transmitters off Cat Island in the Bahamas since 2010 in order to systematically research the way of life and behavior of the animals for the first time. "How are you supposed to protect a species you hardly know about?" Asks Brooks. According to Brooks, Cat Island is the only island in the world where the sharks are found in large numbers off the coast.
The island lies on the edge of the American continental shelf. The Atlantic deep sea stretches right up to the coast - an ideal habitat for deep-sea fish species such as blue marlin, tuna and white fin sharks. "It was like a dream," says the marine biologist Lucy Howey, who leads the research team, which also includes Brooks and Demian Chapman, about her work in the Bahamas. “We no longer believed that we would find larger numbers of white-fin sharks anywhere.” The scientists took advantage of the opportunity and equipped around a hundred white-fin sharks with tracking devices to record their movement data. It turned out that although the sharks travel long distances in the open Atlantic, they spend a large part of the year in the sheltered waters of the Bahamas.
The scientists also discovered that white fin sharks spend 93 percent of their life between the surface of the water and a depth of 100 meters. In this marine zone, fishermen also hunt tuna and other species - this explains the decline in the number of sharks. One way to protect the species is to re-regulate fisheries in these areas. Longline fishing has been banned in the waters of the Bahamas since the 1990s, and all shark species have been banned from trading since 2011. Such sanctuaries are essential if the shark population is ever to recover.
But also around Cat Island the species is rarer than the scientists originally thought. In total only 300 white fin sharks live there. Lucy Howey's researchers came to this conclusion because in the five years in which they tagged sharks, a large number of individuals went online several times. This means that in the scene of the documentary "Blue Water, White Death" mentioned at the beginning, more white-fin sharks crowded around a whale carcass on a single day than can be observed over a whole year in their most important habitat today.
The researchers do not know whether there are any other large stocks anywhere in the oceans. Deep sea white fin sharks are commonly spotted in the Red Sea, off the Cayman Islands, and around Hawaii. But they are mostly single animals or small groups. To protect the sharks, Howey's team now wants to solve another riddle: Many females off Cat Island were pregnant, but there is no evidence that they will give birth to their young there. "We have never seen boys in the Bahamas," Howey says. “If we know the breeding areas, we can try to put the areas under protection. That would be an important step to preserve the species. "
Time cannot be turned back, the relatively intact seas and the abundance of fish that still existed in the 1950s are almost unimaginable for us. One of the few regions that are excluded from this development is the sea around Cuba. The trade embargo that the US had imposed on the socialist Castro regime for fifty years not only hindered the island's economic development, but also the exploitation of natural resources off its coasts. The marine protected areas off Cuba have therefore largely remained untouched.
The Cubans are currently working on a plan to protect sharks even after the blockade is over. Cuban biologists have been studying catches of deep-sea fishermen since 2010. The results astonished scientists all over the world: White-fin sharks were not only the third most common species, there were also adolescent and very young specimens. So maybe it won't be long before the nursery of the deep-sea white fin shark is found and placed under protection.
Read all the articles in our shark series here.
(NG, issue 08/2016, page (s) 64 to 75)
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