Great White Shark Research Dives to New Depths
False Bay’s famous Great White Sharks are still patrolling Seal Island in the hope of catching this season’s young seals unawares. Their presence at Seal Island at this time of the year provides an ideal opportunity for in-depth research and scientists at the Save Our Seas Shark Center are taking this literally….
Great white shark research in False Bay is diving to a new level this month as a scientific research vessel, the M.Y Save Our Seas, arrives to assist Save Our Seas Foundation scientist Alison Kock with her work on great white sharks around Seal Island.
The boat, which is owned by the Ocean Research Group, is being made available for the Save Our Seas Foundation (SOSF) to conduct marine conservation research around the world. A three-person submersible is supplied with the ship. The submersible provides a unique platform and rare opportunity to try to gain a better understanding of the interactions between white sharks and their prey at Seal Island.
Great white sharks patrol Seal Island because it hosts a large breeding colony of Cape fur seals. Their general hunting strategy involves swimming at depth to launch spectacular attacks on the seals above, whose dark bodies are silhouetted against the light of the ocean’s surface. False Bay is the only known place in the world where white sharks predate at such a high frequency on seals. One of the reasons proposed for this extraordinary high predation rate is the topography of the island, which may provide the ideal landscape for these tactics. Sonar has allowed for some mapping of the area, but the submersible will allow for a detailed inspection of the white shark’s hunting ground.
A second objective of the research is to do a survey of the potential prey for white sharks around the island. Previously it was thought that white sharks only visit the Island to predate on Cape fur seals, however, recent unpublished data has revealed that white sharks also predate on fish in these waters.
Alison’s tagging studies and observations of predations on seals have shown that many sharks do not respond to chumming and do not visit the research or cage diving boats even though they are in close proximity. The submersible will allow Alison and her SOSF team to count more accurately the numbers of sharks in the area and compare these findings to counts of sharks taken from the surface.
The ship will spend much of its time anchored a few hundred metres away from Seal Island, so not to disturb the seals, natural predations, cage diving operations or Alison’s standard SOSF research boat. No chumming or baiting will take place from the ship.
For more information about SOSF projects please visit www.saveourseas.com
Cheryl-Samantha Owen of Save Our Seas
That there is still much to be learnt about how sharks and their prey interact, is evident from new research reported on by Monique Fallows of Apex Shark Expeditions in their July 2010 Newsletter, Shark Bytes. She describes research that shows how seals are able to detect the vortices of fish they are hunting with their whiskers. This greatly enhances the seals ability to hunt. Monique and Chris Fallows suspect this same ability could enable seals to detect when they in turn are about to be preyed on by a charging shark. On numerous ocassions, Chris and Monique have documented seals leaping out of the water split seconds before an attacking shark hurtles through a group of seals. For nearly five years now Chris has hypothesized that the seals are detecting the approaching pressure wave ahead of an attacking shark. The action happens so fast that it is invisible to the naked eye. But the repeated observations of a seal leaping out of harms way, has made them think that the seals are able to detect the pressure wave of water as the Great White propels itself into the middle of a group. This split second warning may make a huge difference between life and death. As with so much in life, timing is everything.