Thursday, 02 June 2016 11:22

Great White Shark Sightings

Winter in the Southern Hemisphere is known as the best season to view Great White Sharks. Here in Gansbaai, we have sharks all-year-round, but Winter is still traditionally considered as the best season. There are a few contributing factors, such as the fact that there are more sharks hanging around Shark Alley during Winter, the water visibility improves and the water temperature is a few degrees warmer than in Summer. Thanks to the Great White Shark’s rete mirabile, they are able to raise their body temperature about 10’C warmer than that of the surrounding water, which in layman’s terms relates to the sharks being a little lazy when the water is cold and when the water is warmer, they feel a little friskier. The big males make their appearance in winter, just in time for the Cape Fur Seal pups to take their first plunge into the Atlantic and test their aquatic skills. Generally, we see more females than males during Summer and more adult males during Winter.

Published in Latest News
Monday, 09 February 2015 08:19

What colour is the Ocean?

Great White Shark Gaudalupe

If you were to ask someone what colour is the ocean, chances are that they would answer that it is blue. For most of the world's oceans, their answer would be correct. Pure water is perfectly clear, of course - but if there is a lot of water, and the water is very deep so that there are no reflections off the sea floor, the water appears as a dark navy blue. This is due to the absorption and scattering of light; the blue wavelengths of light are scattered. In water, absorption is strong in the red and weak in the blue, thus red light is absorbed quickly in the ocean leaving blue light to be reflected.

Particles suspended in the water will increase the scattering of light. In coastal areas runoff from rivers, re-suspension of sand and silt from the bottom by tides, waves and storms and a number of other substances can change the colour of the near-shore waters. Great White Shark GansbaaiFine mineral particles like sediment absorb light in the blue part of the spectrum, causing the water to turn brownish in case of massive sediment load.There are other substances that may be found dissolved in the water that can also absorb light. Since these substances are usually composed of organic carbon, researchers generally refer to these substances as coloured dissolved organic matter, CDOM for short.

Phytoplankton can also contain substances and pigments that absorb certain wavelengths of light, which alters its characteristics. Phytoplankton are very small, single-celled plants, generally smaller than the size of a pinhead that contain a green pigment called chlorophyll. All plants (on land and in the ocean) use chlorophyll to capture energy from the sun and through the process known as photosynthesis convert water and carbon dioxide into new plant material and oxygen. Phytoplankton preferentially absorb the red and blue portions of the light spectrum and reflect green light. Accordingly, as the concentration of phytoplankton increases in the water, the colour of the water shifts toward the green part of the spectrum. The basic principle behind the remote sensing of ocean colour from space is this: the more phytoplankton in the water, the greener it is....the less phytoplankton, the bluer it is.

Coccolithophorids are phytoplankton which create microscopic spheres composed of calcium carbonate plates (called coccoliths). The bright white calcium carbonate spheres are excellent at reflecting light and produce the milky turquoise-blue colour of a coccolithophorid bloom.

Then there’s Zooplankton which feeds on the Phytoplankton and the pigments are then absorbed by the Zooplankton. Viruses, believe it or not play a role in the colouring of the ocean too. Viruses selectively infect and kill certain plankton which has a chain reaction affect on the colour of the ocean.

 

And at this stage you may be thinking to yourself: how is it possible that organisms so tiny can affect the ocean which is so vast? Well then I’ll leave you with this fact to ponder upon: More than 90% of the living biomass of the ocean is invisible to the naked eye!

By: Inge Altona-de Klerk

Published in Latest News
Wednesday, 11 February 2015 08:26

I’m FINished with FINS

Love, that curious, chemically charged emotion which we feel towards our favourites, will be celebrated again on Valentine’s Day, this coming Saturday. (And yes, it is my pleasure to have reminded you . . .) If you are reading this, then there is no doubt in my mind that you are a shark lover! And so why not combine the two? Valentine’s Day with Sharks as the emphasis? How preposterous, right?! Shark lovers will probably find this idea adorable but really, what’s the relationship between sharks and couples? 

Well, we all know that shark fin soup is usually a must-have core dish served at Chinese weddings. The team from wedding.com.my aims to raise awareness under their platform to encourage their fans to not feature shark fin soup at wedding banquets. Co-founder of Wedding.com.my, Petrina Goh, told Vulcan Post said that “The whole idea came about when we were thinking… What will be a better way for couples to celebrate their love while doing a good cause at the same time?”

In March 2014, Shark Savers Malaysia (SSMY) was launched and powered by Malaysian volunteers with the support of corporate pro bono resources and local NGO partners. The Malaysian government instituted a ban on shark fin soup at all official state level dining and entertainment in October 2014. 

The wedding.com.my team planned a 3-part event for Valentine’s Day – the main event being the Shark Savers Couple Challenge where they aim to raise public awareness and hand out pledges which says “I’m FINished with FINS”. As an online wedding marketplace, they feel that they have a strong social responsibility to bring awareness to their 200,000 bridal community, since shark fin soup is mostly consumed at wedding banquets.

According to the latest reports, Malaysia is globally ranked 8th for shark catchment and 4th for shark fin imports. Hopefully the efforts of wedding.com.my and Shark Savers will filter through the Malaysian population and help to reduce the above mentioned statistics. 

Conversely, what will you and I be doing to show our love for sharks this Valentine’s Day?

Well, let’s look at what we can do:

  • Take your loved one for a walk on the beach, clean up some debris and then enjoy a lovely romantic picnic on the beach at sunset.
  • Buy your lover a t-shirt or jewellery from a shark conservation organisation.
  • Adopt a shark as a gift for your Valentine!
  • Donate funds to a shark NGO on behalf of your Sweetheart.
  • Spend a day volunteering together at a shark organisation.
  • And on Valentine’s Day, as with every other day of the year, be the best Shark Ambassador you can be! Say no to shark products!

 Wishing you all a very Happy Valentine’s Day!

Published in Latest News
Thursday, 12 March 2015 08:12

White Shark Projects

Published in Latest News
Wednesday, 27 May 2015 08:50

Great White Shark Pups

Very little is known about the location of mating and pupping of Great White Sharks. A Great White Shark birth (and mating) has yet to be photographed/filmed/or otherwise documented anywhere in the world!  They are ovoviviparous, give birth to 2-14 live pups, and may only produce 4-6 litters in a lifetime. The size of newborn pups can be up to 1.5m, and they are highly mobile from birth, further complicating our understanding of where they are born.

Due to the warmer waters brought on by this year’s El Niño, baby shark season has officially begun off the Southern California Coast. White sharks throughout the world move inshore during certain seasons. It is very rare to see adult Great Whites along the Californian coastline. However, the presence of large adult females and then the immediate presence of young pups (<1.5m) strongly suggests that these waters are also a white shark pupping ground from spring – early summer

In Southern California, white shark pups favour many of the same coastal fish species that humans do, like halibut.  So it should come as no surprise that white shark pups are often caught accidentally by coastal fishermen as bycatch.     

Dr Chris Lowe and his students took advantage of this great opportunity to work with local fishermen in the area in order to study baby white sharks.  From their catch/tag/release study, the Lowe Lab found that these white shark pups follow fairly predictable behaviours inshore, staying shallower than the “isotherm” at 60m depth.  Isotherms are boundaries in the water column between warm surface waters and cold deep waters. White shark pups don’t stray deeper than the 60m mark, whether they are in relatively shallow waters or in the deeper waters of the continental slope.  This shows that their choice in habitat relates to water temperature. 

Dr. Lowe and his team release a juvenile white shark back to its inshore waters.

Fewer large predators and an abundance of food, like stingrays and flatfish, draw sharks to the shallower waters

The great white shark is most commonly associated with the coasts of Australia, California and South Africa, but there have been occasions when this increasingly rare animal has been spotted in the Mediterranean. Some experts believe that the Mediterranean is a nursery where great white sharks give birth. The Sicilian channel, near the Italian island of Lampedusa, is the only location in the Atlantic region where both pregnant females and newly born great whites have been sighted. The warm waters of this particular area of the Mediterranean are high in nutrients and attract large pelagic fish, dolphins and turtles which form the staple diet of great whites. This area is a shallow shelf area which keeps the young in warm water throughout the year and reduces competition from blue and mako sharks.

Interesting facts obtained from Dr Lowe and his team:

While it’s rare for white sharks to become stranded on the shore, baby salmon sharks, a close cousin to the white shark, will often strand themselves because of a bacteria that infects their brain and causes them to die, according to Dr Lowe.

85% of all the great white sharks that are by-caught in their study area were <1.75m in length 

These sharks were often found alive when the soak time of the fishing nets was less than 20hr

When released, 92.9% of the pups survived - those are some tough babies!

Published in Latest News
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