Fróðskaparrit - 01.01.1992, Side 16

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THEINTERNATIONAL RESEARCH . ..
IWC Scientific Committee, May 1989 (unpublished). 1-
20.
Raga, J.A. and Balbuena, J.A. In press. Parasites of the
long-finned pilot whale, Globicephala melas (Traill,
1809), in European waters. Rep.int.Whal.Commn
(Special Issue 14).
Age determination and tooth structure
The deposition rate of dentinal and cemen-
tal layers is one growth layer group (GLG)
per year. Five types of mineralisation
anomaly were recognised. Their incidence
varied according to age, sex and state of
maturity and they are at least partly of sys-
temic origin.
The pattems of occurrence of some of
these anomalies (cemental disturbance and
dentinal resorption) were significantly dif-
ferent between pilot whales landed in the
Faroes and pilot whales stranded on the
Icelandic coast.
Comparison of tooth mineralisation
anomalies between different regions of the
N.E.Atlantic - Iceland and the Faroes - con-
tinues, mainly from increasing numbers of
Icelandic animals from mass strandings
(Lockyer, pers. comm.).
Lockyer, C. 1989. Preliminary report on pattems of deposi-
tion of dentine and cement in teeth of pilot whales,
genus Globicephala. Paper SC/41/SM4 presented to the
IWC Scientific Committee, May 1989 (unpublished). 1-
17.
Lockyer, C. In press. A report on patterns of deposition of
dentine and cement in teeth of pilot whales, genus
Globicephala. Rep.int.Whal.Commn (Special Issue 14).
Growth, mortality and survivorship
The mean size at birth was estimated to be
177.6 cm and 75 kg, with no significant dif-
ferences between sexes. Males grow faster
and become larger than females. They
attain a maximum size of 625cm in length
and 2320kg in weight, and females 512cm
and 1320kg respectively. The mean length
for whales older than 25 yrs was 570cm for
males and 446cm for females. Growth
appeared to fall into four phases: early
post-natal, juvenile, young adult, and pre-
physically mature adult, with a rapid
growth rate in the first phase and a declin-
ing rate as physical maturity was
approached. The growth curve in both
sexes was uncomplex with no obvious sec-
ondary pre-pubertal growth spurt. Physical
maturity was reached at a length of c.
570cm and between 25 and 30 years of age
in males, and c. 425cm and c. 30 years of
age in females.
Longevity was greater in females, which
reached over 59 yrs, while males reached
46 yrs. The mean age of females was 15.6
years and of males 11.8 years. Overall mor-
tality rates were higher in males, and mean
estimates ranged from .0745-.0817 in
males and .0622-.0737 in females. The
females exhibited a high mortality in the
juvenile phase, followed by a period of rel-
atively low mortality during mid-life, and
finally a steeper mortality in the older age
classes. The males also showed highest
mortality in the juvenile phase, followed by
a steady decline with age. Part of the high
mortality in mature males may be related to
mating-related competition and fighting, as
suggested by the significantly higher
occurrence of tooth scars in bulls (Bloch,
1992).
Three schools exhibited a growth pattem