Tuesday, November 15, 2011

SPOT Tags - quod erat demonstrandum!

White shark displaying damage to the dorsal fin as a result of SPOT tag deployment breaks the water at Gansbaai, South Africa during a Marine Dynamics cage diving trip. Photo courtesy of Michelle Wcisel, Marine Dynamics.


We present 15 individual cases of sub-adult white sharks that were SPOT tagged in South Africa from 2003–2004 and have been re-sighted as recently as 2011.

Our observations suggest SPOT tags can cause permanent cosmetic and structural damage to white shark dorsal fins depending on the duration of tag attachment.

SPOT tags that detached within 12–24 months did not cause long term damage to the dorsal fin other than pigmentation scarring. Within 12 months of deployment, tag fouling can occur.
After 24 months of deployment permanent damage to the dorsal fin occurred.

Great white shark dorsal fin with SPOT tag present over 24 months after deployment.
(A and B) - tag is showing excessive fouling and fin is leaning to the left as a result of the weight; images taken in 2005 at Mossel Bay and without the tag (C and D) and with resulting hole and fin degradation after tag detachment; images taken in 2009 at Gansbaai.

A shark survived this prolonged attachment and there seems little compromise on the animal's long term survival and resultant body growth.
This is the first investigation detailing the long term effects of SPOT deployment on the dorsal fin of white sharks.

The paper is open access - read it!
Nothing to add to what I said here - fix the bloody gizmo!

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