The white shark, or more commonly known as a great white, has peaked the interest of humans maybe more so than any other species in the ocean. Shark week, which has almost become a television holiday at this point, centers much of the content on the great white.
The interest in great whites has also helped increase the ability for researchers to study them and we have begun to learn more about breeding habits, feeding habits, populations, and distances traveled. As new technologies are introduced, researchers are finding new ways to track and monitor these amazing animals.
For the first time, new research has estimated the total number of adult sharks across the Australian region to be around 2,210 and the total Australian number, including juvenile, to be around 8000-10,000 white sharks. The researchers do point out that they were lacking data on juvenile sharks in one region so a estimate was made based on the findings from other regions.
The data was compiled from CSIRO researchers working with Australian and New Zealand scientists in the National Environmental Science Program though genetic analysis to determine the populations.
The new method of genetic analysis is widely considered much more efficient and effective than old methods. Previously, to determine populations, researchers had to rely on sources such as historical catch data or electronic tagging for some species.
Genetic Analysis works by using close-kin mark-recapture which takes a tissue from a sample shark, alive or dead, obtaining a genetic profile of the shark, and then compares that tissue to all the other sharks to determine if they are related and if they are, how?
The researchers compared the genetic data from juvenile white sharks to look for half-sibling pairs which are animals who shared either a mother or a father. The half-siblings are the close-kin side of the problem. The chances that the researchers find this information is determined by the size of the adult population and the survival rate of adult sharks.
The higher number of sharks, or sharks with low survival rates, make it less likely to find siblings in the samples and the connection researchers are able to make allows them to make a much more clear estimate of the population.
In Australia, white sharks have been protected since 1999 under the Federal Environment Protection and Biodiversity Conservation act. Even under this protection, researchers found that the population growth or decline of the white shark has been flat.
Given that, when looking at specifics, the population growth for juvenile white sharks is much more uncertain. Whites take 12-15 years to mature and assuming the protection of the species reduce juvenile mortality rate, any protection efforts will not be apparent in the adult population until the next 5-10 years.
With the ability to monitor white sharks through tagging and estimating populations more accurately through genetic analysis, researchers will be able to monitor the population health of whites. Based on findings, we will be able to learn if current protections are working as we hope and hopefully, incorporate new methods to better stabilize such an important animal in the eco-system.