Page 4 - Carcharodon2001

ANNALES · Ser. hist. nat. · 11 · 2001 · 2 (25)
Alessandro DE MADDALENA et al.: AN ANALYSIS OF THE PHOTOGRAPHIC EVIDENCES OF THE LARGEST GREAT WHITE SHARKS, ..., 193-206
TOT
PP2-PP1
PP2
Fig. 1: Measurements of the white shark Carcharodon
carcharias (Linnaeus, 1758) used in this work, based on
Compagno (1984) and Mollet et al. (1996): totallength
with caudal fin in depressed position (TOT), total
/ength with caudal fin in natura/ position (Tln), pre-
caudal /ength (PRC), prepelvic length (PP2), pre-first
dorsa/length (PD1), prepelvic-prepectoral space (PP2-
PP1). (Drawing: A. De Maddalena)
SI. 1: Mere belega morskega volka Carcharodon car-
charias (Linné, 1758), uporabljene v tem delu na osnovi
Compagna (1984) in Molleta et al. (1996): ce/otna iz-
tegnjena dol.iina (TOT), celotna dol.iina v naravni legi
(Tln), predrepna doltina (PRC), dol.iina do trebusne
p/avuti (PP2), doliina do korena prsne p/avuti (PD1),
razdalja od zaéetka prsne p/avuti do zaéetka trebusne
p/avuti (PP2-PP1). (Risba: A. De Maddalena)
ing the girth of the body (Casey & Pratt, 1985), but pre-
cise girth was never reported by the sources. For these
reasons we commented on the weight reported only in a
few cases.
The mode! of a white shark preserved in the Museum
of Zoology in Lausanne, Switzerland, is a mould recon-
structed via casts from the originai body of the specimen
caught in Sète, France, on 13'h October 1956: this is the
largest white shark specimen whose complete mor-
phometrics (made following Compagno, 1984) are
available world-wide (De Maddalena et al., 2002). Con-
sidering that the size of this specimen is very dose to 6
metres (583 cm TOT, 565 cm Tln and 458 cm PRC), its
measures can be utilised as a useful reference to effect
precise estimates of the size of other specimens within
5-7 metres length range (Tab. 2).
For every specimen we estimated three lengths (from
Compagno, 1984 and Mollet et al., 1996): the total
length with the caudal fin in the depressed position
(TOT), which is also the maximum length, the total
length with the caudal fin in the natura! position (Tln),
and the precaudal length (PRC) (Fig. 1). To effect the es- some cases, being very old photos, the mean height of
196
timates we proceeded as follows. First of ali we chose a
reference of the valuable size, as is the height of a man
(estimated by comparison with other persons near him)
very dose to the shark. On this basis we then estimated
the length of a segment of the shark that was in the
photo not or just slightly distorted by the perspective,
choosing the most suitable one from the parameters in-
dicated by Compagno (1984), depending on the case :
the prepelvic length (PP2), the pre-first dorsal length
(PD1 ), the space between the ori gin of the pectoral an d
the origin of the pelvic fin, corresponding to the differ-
ence between prepelvic length and prepectoral length
(we called it the prepelvic-prepectoral space, and we
indicated it as PP2-PP1) (Fig. 1). Finaliy we m ade a ratio
between this partial length to the same partial length of
the Lausanne specimen reported in De Maddalena et al.
(2002), and thus obtained the three lengths TOT, Tln
and PRC (Tab. 2).
The problems encountered at the moment when an
accurate estimate of the size of a large white shark from
photographic evidences was effected were severa!.
Greater difficulties occurred due to the foliowing factors:
a) position of the photographer not exactly latera! in re-
spect to the shark; b) distance subject-photographer
much too short; c) excessive doseness of the subject to
the edges of the field of vision; d) difficulties in the
evaluation of the size of the reference; e) different dis-
tances between shark and photographer and between
reference and photographer; f) the smaller the segment
of the shark that can be correctly estimated, the greater
the possibility of an errar.
Ali these factors made it impossible to use, in this
work, the numerous photos coliected in the ltalian Great
White Shark Data Bank, and thus included herewith
only some of those that seem suitable for this kind of
study. The necessity to choose correctly the longer seg-
ment not distorted by the perspective for the estimate
has emerged clearly. We saw that the prepectoral length
(PP1) could be noticeably deformed and shortened
when the shark was suspended in vertical position.
Namely, the reference has to be large, such as the entire
height of a man or at least a large part of him, and it has
to be placed exactly on the same piane as the shark: that
is particularly important when a dose-up was made.
Evaluating the height of the man by comparison with
other persons in proximity, we also considered that in
the persons had to be somewhat smaller than today. Ali
the estimates of the men's height indicated herewith in-
clude the heels of their shoes and hats, if present. The
estimates presented herewith are not the maximum sizes
possible for these specimens, but are the sizes that, in
our opinion, are doser to the real ones.