Grootwithaai gedissekteer

On Friday the 26th of June, a local fisherman Pikkie Smal contacted the Dyer Island Conservation Trust (DICT) to report the carcass of a Great White Shark (Carcharodon carcharias).

The shark was found washed up at De Gruis, Franskraal. On arriving, Wilfred Chivell and the team managed to confirm that the shark was an adolescent female. The specimen quality was very decomposed and had likely been dead for a number of weeks given that her skin pigmentation was badly bleached. She measured at 3.2meters, pre caudal length.  Interestingly  the  tail was missing, with it she would have measured closer to 3.5m (TL).

The shark was moved to the International Marine Volunteer (IMV) lodge in Kleinbaai. I joined the team at this point and on first inspection of the shark, three bites were visible on the underside as well as a large propeller injury towards the tail region. The shark would have degraded considerably in any attempt to transport her to Cape Town and freezing was not an option.

The Department of Environmental Affairs therefore permitted Meredith Thornton, DICT research and IMV co coordinator and myself to perform the necropsy on site. Marine biologists Georgia French and Simone Rizutto from Sussex and Stellenbosch University assisted considerably in both the retrieval and dissection. The first organ exposed when cutting into any shark, is the enormous liver.  Aside from being the main detoxification unit, the liver is both a buoyancy aid and an ener-gy reserve. This female sharks liver weighed 59kgs and was almost liquefied- it was by far the most grueling component to remove and weigh! The Necropsy was completed in five hours. All measurements and necessary samples were collected, including the stomach which had the remnants of seal carcasses inside of it. The impressive jaw was cleaned down to the cartilage. The information collected from this female specimen will go towards several crucial studies improving our knowledge in areas such as genetics, diet, age/growth and toxicology.

The DICT also successfully retrieved a deceased male white shark back in June 2012. The 3.8m (TL) male washed ashore on Dyer Island. The government necropsy revealed no obvious cause of death despite 6 cape fur seals in its stomach! With the latest female shark, the propeller laceration could have caused a fatal blow- although this is only speculation and we will never truly know if the propeller and bite wounds occurred before or after death.

The other possibility is transient Killer Whales (Orchinus orca) which have been documented to bite the fluke from dolphins when hunting.

The DICT are exceptionally grateful for Pikkies’ vigilance and quick contact; we encourage the local public to phone in at any time if they sight something of interest along our coasts. Phone: 082-907-5607 or 082-801-8014.

Alison Towner, DICT Marine Biologist

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