White shark Protection

Considering the incredible number of between 150 - 200 million sharks destroyed each year, we need to look at the natural biology of sharks to fully understand the potential threat of extinction to these species. Most sharks are slow growing, have late maturation and low fecundity and this is the shark's downfall. They cannot replace their stocks to keep up with human exploitation, such as say, sardines can. Lets look at the Great White Shark. The Great White Shark female takes approximately 15 years to become sexually mature, and the male about 8 years. At these ages the female will be around five meters long and the male around four meters long. The Great White Sharks' fecundity is low, so the female may possibly only give birth to several litters of pups in a lifetime and these litters are relatively small, ranging from about seven to eleven pups in a litter. The white shark is just an example, and if you look at all species, you find some which give birth to only one pup and some such as the Sandbar shark which only become sexually mature at about 25 years old. So due to the shark's inability to reproduce quickly, stock replacement is not occurring, and subsequently the populations of the world are fast diminishing. In fact they are being wiped out far quicker than most people realise, with many species critically endangered and some species literally on the brink of extinction. 

The Great White Shark is now protected in South Africa, California, South Australia and Tasmania, and although this is only one of almost 400 species of shark, its protection is a step in the right direction. The Great White is a key stone species on this planet and its protection, subsequent media attention and high public profile allows us to use it as a battering ram to push for the protection of other shark species. 

White shark

About the Great white shark

Great white sharks are at the very top of the marine food chain. Feared as man-eaters, they are only responsible for about 5-10 attacks a year, which are rarely fatal. Great whites are ultimate predators. Powerful streamlined bodies and a mouth full of terrifyingly sharp, serrated teeth, combine with super senses that can detect a single drop of blood from over a mile away. Hiding from a great white isn't an option as they can detect and home in on small electrical discharges from hearts and gills. Unlike most other sharks, live young are born that immediately swim away.

Scientific name: Carcharodon carcharias
Rank: Species

White shark

The great white shark, Carcharodon carcharias, also known as great white, white pointer, white shark, or white death, is a large lamniform shark found in coastal surface waters in all major oceans. The great white shark is very well known for its size, with the largest individuals known to have approached or exceeded 6 metres (20 ft) in length and 2,268 kilograms (5,000 lb) in weight. It reaches maturity at around 15 years of age and can have a life span of over 30 years. The great white shark is arguably the world's largest known extant macropredatory fish and is one of the primary predators of marine mammals. It is also known to prey upon a variety of other marine animals including fish, pinnipeds, and seabirds. It is the only surviving species of its genus, Carcharodon.
The best selling novel Jaws and the subsequent blockbuster film by Steven Spielberg depicted the great white shark as a "ferocious man eater". In reality, humans are not the preferred prey item of the great white shark.
  
Reproduction
 Little is known about great white shark behaviour in the way of mating habits. Birth has never been observed, but pregnant females have been examined. Great white sharks are ovoviviparous (eggs develop and hatch in the uterus, and continue to develop until birth). The great white has an 11 month gestation period. The shark pup's powerful jaws begin to develop in the first month. The unborn sharks participate in intrauterine-cannibalism: stronger pups consume their weaker womb-mates. Delivery is in spring and summer.
Almost nothing is known about mating behavior. Some evidence points to the near-soporific effect of a large feast (such as a whale carcass) possibly inducing mating.
Great white sharks reach sexual maturity at around 15 years of age. Maximum life span is believed to be more than 30 years.

 Adaptions
Great white sharks, like all other sharks, have an extra sense given by the Ampullae of Lorenzini, which enables them to detect the electromagnetic field emitted by the movement of living animals. Every time a living creature moves it generates an electrical field and great whites are so sensitive they can detect half a billionth of a volt. Even heart beats emit a very faint electrical pulse. If close enough the shark can detect even that faint electrical pulse. Most fish have a less-developed but similar sense using their body's lateral line.
To more successfully hunt fast and agile prey such as sea lions, the great white has adapted to maintain a body temperature warmer than the surrounding water. One of these adaptations is a "rete mirabile" (Latin for "wonderful net"). This close web-like structure of veins and arteries, located along each lateral side of the shark, conserves heat by warming the cooler arterial blood with the venous blood that has been warmed by the working muscles. This keeps certain parts of the body (particularly the brain) at temperatures up to 14 °C (25 °F) above the surrounding water, while the heart and gills remain at sea-temperature. When conserving energy the core body temperature can drop to match the surroundings. A great white shark's success in raising its core temperature is an example of gigantothermy. Therefore, the great white shark can be considered an endothermic poikilotherm, because its body temperature is not constant but is internally regulated.

http://en.wikipedia.org/wiki/Great_white_shark

Global range highlighted in blue

White shark at Isla Guadalupe, Mexico

 

conservation  status

Rasprostranjenost Bele ajkule

Gotovo sve velike bele ajkule žive u obalnim i priobalnim vodama koje imaju temperaturu između 12 i 24 °C (54 ° do 75 °. Najviše ih ima pri obalama južne Australije, Južne Afrike, Kalifornije, ostrva Gvadalupe, a ređe su u Sredozemnom i Jadranskom moru, kao i oko Novog Zelanda gde su zaštićena vrsta. Takođe se ponekad mogu naći u tropskim vodama, kao i na Karibima, te su primećene i u vodama Mauricijusa, Madagaskara, Kenije i Sejšelija.

Status ugrozenosti ove vrste

Može se naći i na dubinama do 1280 metara, ali obično ne živi tako duboko. Najčešće živi do dubine od 900 metara. Živi u slanoj, ali i u braktičnoj vodi.

Moze se naci u svim morima sveta. Vise voli tople do umerene vode . Pojedine jedinke zive i u hladnim vodama oko Juzne Australije , Nove Skotske i Islanda.

Na slici su crevenom bojom prikazana podrucija rasprostranjenosti belog morskog psa

http://tehnika.krstarica.com/l/nauka/ajkula-remek-delo-evolucije/

Bela Ajkula

 

Sistematika:

RED: Morski psi      
PORODICA:Laminidae    
ROD I VRSTA:Charcharodon charcharias 

Belu ajkulu  nazivaju i ljudozder ili bela smrt. Ovom putniku po svetskim morima, mozemo pripisati veliki broj napada na kupace i manje camce.

Telesne mere: duzina oko 3-6 m, moze da bude i duza  ,  tezina prosecno od 700 kg do 1200 kg

Razmnozavanje: O njenima osobinam prilikom parenja se zna jako malo. Poznato je da radjaju zive maldunce i da zenka okoti jedno mladunce.

Nacin zivota: Ponasanje- samotnjak koji mora stalno da bude u pokretu

Hrana: jede sve vrste riba i toplokrvnih zivotinja , koje moze da ulovi

Zivotni vek: Nepoznat

Staniste: Moze se naci u svim morima sveta. Vise voli tople do umerene vode . Pojedine jedinke zive i u hladnim vodama oko juzneAustralije , Nove Skotske i Islanda.

Zastita vrste: Beli morski pasje stalno u pokretu , sto je razlog da se tacan broj jedinki ne moze utvrditi. Pretpostavlja se da nije brojna vrsta.

Beli morski pas napda tako , sto podigne vrh svoje njuske. Celjusti isturi napred i otvori ih , pa hvata svoju zrtvu kao u zamku.

Ishrana i nacin lova

Skoro svako zive bice u okeanu moze biti zrtva belog morskog psa. Ukoliko je veca , utoliko je zadovoljniji. Tune , ribe nalik na skuse i sabljarke su njegova najomiljenija hrana, dok morski lavovi, foke i delfini za njega nisu nista drugo nego prihvatljivija "uzina'', iako ih pojede.
Beli morski pas lovi pojedinacno, mada se ponekad oko mrtvog plena moze skupiti i veci broj jedinki i to zato sto razlivena krv primami i ostale bele ajkule koji su u blizini.
O kolicini dnevnog obroka ove ribe , nema podataka, jer je kolicina koju pojede zavisna od temperature vode i plena koji mu je u blizini. Pretpostavlja se da beli morski pas prozdire novi plen bez obzira na to , sto je kratko vreme pre toga pojeo veliku kolicinu hrane. Ako je to potrebno, moze da provede duzi period vremena bez hrane.

Od zivotnog znacaja za beog morskog psa je njuh. To je najznacajnije culo, kojim pronalazi plen u vodi. Na vrhu gubice ima hiljade sitnih otvora , koji oblikuju vazan nervni centar.
Zbog svog izuzetnog dobro razvijenog njuha moze da nanjusi i najmanje kolicine krvi u vodi.



Beli morski pas i covek

Pokazalo se da je za veliki broj napada morskih pasa na coveka , odgovoran upravo beli morski pas. O tome svedoce duboki tragovi zuba na rastrganim daskama za jedrenje i camcima, kao i mnogi oziljci na ljudima koji su preziveli napad.

Povrede nastale ujedom belog morskog psa

 Beli morski pas je omiljeni plen sportskih ribolovaca, koji ovakav ulov smatraju najvecimdostignucem u svojoj ribolovackoj karijeri. Belog morskog psa prepoznajemo po izrazenom trouglastom lednom peraju i snaznom repu u obliku polu meseca. Love ih uglavnom iz sporta jer im meso nije narocito ukusno. Meso mirise na urin i izlucevine.
O belom morskom psu se zna neverovatno malo. Posmatranje belog morskog psa u njegovoj prirodnoj sredini su bili neuspesni. Beli morski pas je stalno u pokretu. U akvarijumu ga je vrlo tesko drzati jer ce u tom slucaju tesko preziveti.
 

 Nacin zivota


Vecina naucnika pretpostavlja da kada beli morski pas dostigne odredjenu proporciju izmedju svoje duzine i tezine , promeni svoje zivotne navike. To izgleda kao kad bi zivotinje koje su bile ''zadovoljne'' zivotom uz povrsinu mora , promenile svoje navike i lovista i zauvek nestale u dubinam okeana. Tako se predpostavlja da beli morski pas isto kao i usnaca, posto dostigne odredjenu velicinu , promeni pol i umesto muzijaka postane zenka. Mozda je ovo nacin na koji priroda omogucava prezivljavanje ogranicenom broju jedinki.
Tako samo velika i zdrava riba moze na svet da donese maldunce i doprinese opstanku vrste. Morski psi koji polazu jaja imaju drugaciji nacin zivota.

Karakteristicno ledjno peraje koje viri iz povrsine prilikom plivanja

Posebnosti

Zube ima kao trakasta testera.. Dugi su oko sedam do osam santimetara i trouglastog oblika. Nazubljeni su po rubovima pa im je zbog toga lakse da zgrabe plen. Poput ostalih morskih pasa i beli morski pas, odlomljene ili slomljene zube zameni novim. Zubi su mu poput trakaste testere , stalno rastu i ostaju u celjusti sve dok nije potrebno da zamene stare ili istupljene. Kada beli morski pas izgubi zub , ''traka'' se pokrene i pojavi se nov zub.

Zub belog morskog psa

 Da li ste znali?

Ugriz morskog psa ima snagu od nekoliko tona po kvadratnom santimetru.
Beli morski pas moze da nanjusi kap krvi u 4.6 miliona litara vode.
Ako bi belog morskog psa vukli kroz vodu u ornutom pravcu uggusio bih se ubrzo.
Neki morski psi radjaju zive mladunce a neki polazu jaja.

Beli morski pas mora da pliva 24h dnevno brzinom od 3.5 km/h da bi dobio dovoljno kiseonika u svoj krvotok.

http://en.wikipedia.org/wiki/White_shark
http://animals.howstuffworks.com/fish/great-white.htm