White Shark Projects is a renowned global research organisation which was founded in 1989 and is dedicated to Great white shark conservation. During this time we have had the pleasure of meeting many of these ocean predators. Some of which we have come to recognise as they have visited the Gansbaai area on multiple occasions over the years. One of the Great white sharks that we have come to know is a 3.5 metre male that was nicknamed “Mini Nemo”. This shark has a very distinct pectoral deformity so was fondly named after every marine biologist’s favourite film, Finding Nemo. We have observed “Mini Nemo” for at least the past five years from our cage diving vessel, Shark Team.

“Mini Nemo” – Photo taken by one of White shark Projects on-board Marine Biologists, Tom Slough.

The fact that so many Great white sharks repeatedly come back to Dyer Island, Gansbaai got me wondering……. How long do sharks live?

Well, in recent years scientists have been able to analyse radiocarbon levels in the tissues of marine animals to estimate an age range…… What this basically means is scientists look at pretty stuff and it tells us how old the animals are. They are able to do this because nuclear bomb testing between 1955 and 1963 doubled the amount of carbon-14 in the atmosphere. This carbon-14 fell from the atmosphere into the oceans and was taken up by marine animals that were around at the time. Therefore, tissue from that time period shows a distinct rise in carbon-14 levels when analysed.

Photo shows nuclear bomb testing at the Nevada Test Site, 1955 –Photo credit U.S Air Force.

In 2014, a team at Woodshole Oceanopgraphic Institution in Massachusetts analysed the radiocarbon from the vertebrae of four male and four female Great white sharks captured in the Atlantic Ocean from 1967 – 2010. The results showed an age estimate up to 40 years old for the largest female (5.26 metres) and an incredible 73 years old for the largest male tested (4.93 metres). These findings may indicate that the Great white shark has a similar life course to us and if so these animals may mature slowly like we do (Hamady et al, 2014).

However, the Great white shark has an age rival…… The Greenland shark (Somniosus microcephalus) whose latin name translates to sleepy small head due to its sluggish behaviour (cruising speed of 0.3 m/sec).

Greenland shark – Photo ©Jeffrey Gallantǀ GEERG.ca

The Greenland shark is the second largest carnivorous shark after the Great white and can grow up to a massive 7 metres in length. However, the average size of the animals is usually between 2.5 to 4.5 metres. It is a deepwater species and habitat range extends from the Arctic Ocean and Northern Europe to parts of the Atlantic Ocean. Despite being called a sleepy small head it is now thought that this shark can be an ambush predator, capable of short bursts of speed and may even hunt live seals (Gallant, 2016).

In 2016, a research team at the University of Coppenhagen also used radiocarbon dating to measure carbon-14 absorbed in the eye tissue of 28 sharks caught as bycatch. They revealed an extraordinary life expectancy of at least 272 years and that sexual maturity may not be reached before 156 years. They estimated the life expectancy of the largest shark they tested (5.2 metres) at 392 +/- 120 years old. There is still much debate on the accuracy of using radiocarbon dating to estimate the age of marine animals. However, even the lowest age estimate of 272 years is incredible and makes the Greenland shark the oldest living vertebrate known to science (Nielsen et al, 2016).

Greenland shark in the Saint-Lawrence Estuary, Quebec. Photo© Jeffrey Gallantǀ GEERG.ca

Sharks are slow growing and mature late which means that it is harder for them to recover their populations. This makes them even more vulnerable to the overfishing and environmental pressures they are facing.

It is wonderful to think Great white sharks can live as long as humans and some of them have repeatedly come back to visit Gansbaai over the years. We believe that education is vital in aiding the conservation of these spectacular apex predators globally. We encourage people to come learn more about and experience these magnificent animals for themselves – shark cage dive with us. #WhiteSharkProjects.

You can also learn more about sharks in our last blog.

Great white shark – Photo taken on board Shark Team, White Shark Projects cage diving vessel.

Ready to see Great white sharks yourself? Get in touch.

Written by Georgie Pendell
 August 2018