12 November, 2008
NOTE: No new positions have been recorded for the white sharks since
February 25, 2005.
Why are no new white shark positions being reported?
The satellite tags are expected to operate for a
period of about six months, but this depends on how often the tags
transmit, which in turn depends on how often the sharks surface.
The tags attached to white sharks at The Neptunes
in November 2004 transmitted frequently for four months. Their
batteries may be nearly exhausted.
Another possibility is that the lack of transmissions
reflects the swimming behaviour of the white sharks.
Three of the tagged sharks were last heard from in
Spencer Gulf, SA. When in the shallow waters of Spencer Gulf or
Gulf St Vincent the sharks commonly swim along the bottom for prolonged
periods, probably while feeding on bottom-dwelling fish and rays.
Satellite tags may also fail to transmit due to battery
passivation (deposits on the electrodes), or tag failure.
A break in transmissions is an anxious time. What
are the sharks doing that may reduce the transmissions? Have the
tags failed? Only time will tell. |
