Engineering - Royal Australian Navy

Naval Engineering Bulletin • June 2001
HMAS WALLER’s Brush with the
Cookie Cutter Shark
By LCDR Forbes PETERS, RAN
On the 14 May 00 a priority 3 defect signal was received
from HMAS WALLER. A 2.5cm ‘gouge’ had appeared on
the Intercept array protective moulding. Two other
‘delamination’ were observed that hadn’t penetrated the
surface of the moulding. Initial technical prognosis was
difficult without photographic evidence.
On the 31 May 00 several images arrived by e-mail. The
damage was immediately identified by the FEG technical
department as the bite marks of the Cookie Cutter shark.
One of our beloved steel sharks had fallen pray to a 50cm
long shark (Isistus brasiliensis or the Cookie Cutter Shark)
with eyes bigger than his stomach.
The Cookie Cutter Shark
The shark is named after the neat cookie shaped wounds
that it leaves on the bodies of larger fish and marine mammals.
The species has a small cigar-shaped body (up to 50
cm in length), a conical snout and two low, spineless dorsal
fins positioned posteriorly on the body. It is dark brown
dorsally, lighter below, and has a distinct dark collar around
the gill region. The entire ventral Surface is covered in a
dense network of tiny photophores (light producing organs),
which in life
produce an
even greenish
glow.
The shark
has small
erect teeth in
the upper
jaw and
Cookie Cutter Shark Bite from HMAS WALLER’s
Intercept Array Sonar Dome
larger triangular teeth in the lower jaw. The cookie cutter
shark attaches itself to its prey with its suctorial lips, and
then spins to cut out a cookie shaped plug of flesh from
the larger animal (In this case, quite a bit larger). The shark
lives below 1000m during the day and vertically migrates
at night into the surface waters. There have been numerous
reports from the USN on damage caused to submarine
sonar domes. Further information for the ichthyological
inclined can be found in www.austmus.gov.au/fish/species/ibrasil.htm
The moral of the story is “check your towed array” and don’t
always blame the RIB!
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