spy hopping

SMF Article : All about Great White Shark

Who are the great white sharks ?

 

Super predator, the white shark fascinates as much as it scares. Victim of the bad image of sharks in general, it is all the more because of the erroneous label of the « man-eating beast ». An image that is unfortunately well anchored, sometimes supported by cinema. Its large size, giving an impressive character to its attacks, makes it all the more spectacular. However, the man is not part of his diet and the white shark is, of course, much more than that. Studied by researchers and specialists from all over the world, he has not finished delivering all his secrets.

 

Great white sharks biology

 

The white shark (Carcharodon carcharias) can exceed six meters, the males are smaller than the females. Although variations are possible by geographical area, sexual maturity is around 8 or 10 years for males and 12 or 18 years for females. These are viviparas aplacentaires. In other words, the eggs, then the embryos, develop inside the genital tract and are nourished by their yolk sac. So there is no placenta. Embryos also feed on oophagy: absorption of unfertilized eggs overproduced by the mother. The physical aspect of the species is easily recognizable. Their body is fusiform and massive on the front part. It has a color that can vary between individuals, ranging from a more or less dark gray to a gray brown. The underside is white, which creates a contrast of color with the upper part. The snout of the white shark is conical and quite long. As for its jaws, objects of many fantasies, they contain teeth that are renewed and whose total size can reach 6.4 cm. They are, as it were, stored in rows in the jaws of the shark (5 to 6 rows of which 1 or 2 are functional). Life expectancy is estimated between twenty years to 73 years.

 

Geographic distribution and eating habits

 

The white shark is a cosmopolitan species, present in all oceans except the polar regions. The latter still prefers cold, shallow, and warm waters. If their presence sometimes prevents some to enjoy a swim, it is worth noting that no, the human flesh is not on the menu of white sharks. The attacks produced are rare and have occurred under circumstances that led the animal to some confusion. Most injuries involve one to two bites. The shark « tastes » but does not like it. Only, given the power of the animal, the injury in question is often serious and can be fatal. It is important to keep in mind that if white shark attacks on humans are very rare, man’s attacks on him are much more frequent and contribute to the decimation of the species.

In fact, the diet of adults is varied. It includes for example other sharks, turtles, dolphins and small cetaceans as well as pinnipeds (sea lions, seals …), sometimes also crabs and seabirds, squid … Their diet also includes the ingestion of carcasses. An advantageous solution that allows them a major energy input and minimal expenses. Young specimens eats mostly fishes.

 

The Mediterranean Great White Sharks

 

In order to collect and analyze the information available on the great white sharks living in the Mediterranean, the Italian shark specialist, Dr. Alessandro De Maddalena began research in 1996 on the recordings of this great predator found in these waters. He named this research program « Italian Great White Sharks Data bank ». Today, it includes information from 593 recordings of great white shark encounters throughout the Mediterranean Sea, representing the most comprehensive study ever conducted on the great white sharks of this region. We can read that this sharks were undoubtedly much more abundant in the Mediterranean than they are today, explains Alessandro de Maddalena. On October 13, 1959, a 589cm female was caught ff Maguelone, South of France, landed at Sète. This specimen is the largest preserved, available to see at the Zoological Museum in Lausanne, Switzerland. « Of the 593 records of great white sharks, 81 were reported to be measured or estimates as being larger than the 589 cm, the size of the Maguelone specimen. In most cases, the reliability of the reported size is impossible to verify and cannot be accepted or refuted ». Indeed, several cases considered reliable are reported, such as a shark caught off Paliouri, Chalkidiki, Greece circa 1985, which was estimated at 601-618 cm or a female captured in Marseilles on October 15, 1925, which was estimated at 667-687 cm. As for their presence, the specialist explains: « Today, depending on the area, the presence of the great white shark is considered rare or very rare. Having an extensive coastline, Italy is the nation with the highest number of records. Moreover, Italy borders the highest number of seas and includes the highest variability in habitat […] In the Mediterranean, as in other areas of the world, this predator frequents the area close to banks, islands, straits, and channels where prey is more abundant In the study area they can be found in depths ranging from the surface to at least 130 m (maximum depth was recorded off Marzamemi, Italy) ». As for the attacks, Alessandro de Maddalena explains that « The data collected from the Mediterranean, just as elsewhere in the world, demonstrates that white sharks are typically not naturally aggressive toward people ».He also explained : « In total, 55 white shark attacks on humans were recorded in the Mediterranean, including 13 that must be considered doubtful because there is some doubt over the exact identity of the species or because the case itself is considered doubtful […] Human beings are not a usual part of any shark diet, great white shark included. It is presumed that the great white sharks do not regard humans as food and that the large majority of attacks are clearly not motivated by hunger ».

 

Protection of the species

 

Great white shark fishing has been banned for more than 20 years in Australia, Florida and California. The same has been true of South Africa since 1992 and Namibia in 1993. Great white sharks have been included in CITES Appendix II since 2005, after having been included in Appendix III since 2001. The Convention on the International Trade of Endangered Species (Convention on International Trade in Endangered Species of Wild Fauna and Flora), or the Washington Convention, entered into force on 1 July 1975. The latter is an intergovernmental agreement ensuring that international trade in specimens of wild animals and plants does not threaten the survival of the species to which they belong. Thus, CITES controls and regulates the international trade of these specimens, listed in its Appendices according to the degree of protection required. Appendix-III, in which great white sharks were then listed, covers species already listed at the request of a Party that regulates trade and needs the cooperation of other Parties to prevent its illegal or unsustainable exploitation. International trade in specimens of listed species is permitted only on presentation of previously issued permits or certificates. Appendix-II, corresponding to the situation today, concerns species that, although not necessarily threatened with extinction, could become so if trade in their specimens wasn’t closely controlled. International trade in Appendix-II registrations may be authorized and must be covered by an export permit or a re-export certificate. Authorities issuing these permits should do so only if the established conditions are met and if they are satisfied that this will not affect the survival of the species in the wild.

The protection of the species is also effective and legal from a European point of view. The following information comes from the Official Journal of the European Union, concerning Council Regulation (EU) 2019/214 of 30 January 2019. According to the European Regulation, Article 14: « Union fishing vessels shall be prohibited from to fish, to keep on board, to tranship or to land the following species … (b) the great white shark (Carcharodon carcharias) in all waters « . Article 50 also states: « It is prohibited to keep on board, to tranship or to land the species listed below when they are in Union waters […] the basking shark (Cetorhinus maximus) and the great white shark (Carcharodon carcharias) in Union waters.

 

Recent discoveries

A team led by scientists from the Save Our Seas Foundation’s Shark Research Center, Nova Southeastern University (NSU) and the Guy Harvey Research Institute (IRSH), the University’s College of Veterinary Medicine of Cornell and the Monterey Bay Aquarium completed the genome (set of chromosomes and genes) of the great white shark. It was then compared to the genomes of a variety of other vertebrates, including the whale shark (Rhincodon typus) and humans. The work was published in the Proceedings of the American Academy of Sciences, PNAS. The genome has no less than 41 pairs of chromosomes, against 23 pairs for humans. Another result of this study is the very good quality of the gene, which plays a role in both the stability of the genome, but also in the repair of DNA. The findings uncovered many of the great white shark’s incredible abilities, including their genetic adaptability, their ability to heal effectively, and the reasons why great white sharks are more resistant to cancer.

 

 

Another study from Monterey Bay and partner institutions published on April 16 shows that great white sharks would avoid Orcas (Orcinus orca) and would retreat from areas where they came. « When confronted by orcas, great white sharks will immediately vacate their preferred hunting ground and will not return for up to a year, even though the orcas are only passing through » said Dr. Salvador Jorgensen, principal investigator Monterey Bay Aquarium, author of the study. To arrive at the final results, shark electronic tags data were compared with the orc field observations. These tags show that all white sharks began to leave the area a few minutes after brief killer whale visits. Scientists were able to analyze interactions with data from 165 white sharks tagged between 2006 and 2013. One species took advantage of this situation: the elephant seals (Mirounga). In fact, the data showed four to seven times less predation on this species by white sharks, the latter being no longer in this area. It is important to note that the study did not concluded whether those orcas hunted white sharks bullied their competition, to benefit from seals and elephants that are high in calories. Given these results, it is necessary to emphasize that the situation depicted here corresponds to a specific site. The relationship between orcas and white sharks may vary or even be non-existent on other sites. The behavior and diet of killer whales also vary according to the region and the different populations of these cetaceans.

 

MH