Fróðskaparrit - 01.01.1991, Síða 36

40
STUDIES ON THE LONG-FINNED PILOT WHALE
readings were also made with the help of V.
de Buffrenil, Paris, while some from Klaks-
vík, on January 29, 1985 were read with the
help of C. Lockyer, Cambridge.
Later studies have found that by reading
only the dentine, cemental layers in the teeth
of animals older than about 13 GLG’s tend
to outnumber those seen in the dentine
(Lockyer, Desportes and Waters, 1987;
Bloch, Lockyer and Zachariassen, in print,
c), and the age will thus be underestimated.
A reexamination has been made of the
material from New Foundland by reading
both the dentine and the cementum (Kasuya,
Sergeant and Tanaka, 1988b). This has
changed the original readings made by Ser-
geant (1962), such that the older group of
whales now has a higher estimated age. An
attempt was also made to reexamine the
teeth included in the present study following
the technique described by Kasuya and Mat-
sui (1984), using both dentine and cemen-
tum. Two teeth, which had been stored in
glycerine, were cleaned in hot tap water and
70% alcohol. One was then etched in 5%
formic acid for 2-4 hours, and the second
one was decalcified, cut and stained with
haematoxyline. The former process of boil-
ing and storing in glycerine made the stained
tooth totally opaque and impossible to read
again. And the etched tooth was not easier
to read than the original half.
Because of this, age determination of
whales older than about 10-15 years must be
taken with cautious. It must be remembered
that each year class (n) is placed at year n on
the curves, but contains all animals from age
n to age n + 1, so each year class ought, in
fact, to be placed in (n+0.5) year (Fig. 5).
Oddly, some of the schools turned out to
be much more difficult to read than others;
the school from Fuglafjørður, August 21,
1984 was one of them. This phenomenon is
also observed in the material sampled from
1986 to 1988 (Lockyer, in print, a; Bloch et
al, in print, c).
Reproduction. For reproductive study, both
ovaries and at least 1 of the testes were sam-
pled. In all, gonads were taken from 215
whales from 7 different schools (see Table 1).
The testes were weighed, fresh, in the
laboratory, and a slide of testes and epididy-
mis was fixed in 10% buffered formalin for
histological examination, which was per-
formed by G. Desportes (unpublished data).
The ovaries were fixed in 10% buffered
formalin. After weighing, they were sliced at
a thickness of 1 mm in order to find and
count corpora and follicles. The corpora lu-
tei were measured in 3 directions at right an-
gles to each other to the nearest mm and
weighed to the nearest 0.1 g. Corpora al-
bicantia and larger follicles were measured in
2 directions at right angles to each other. The
ovaries have been read by C. Lockyer and G.
Desportes in collaboration with the author.
Contamination. To determine levels of con-
tamination by Hg, Se and persistent or-
ganochlorines, samples of about 10 g each
were taken of muscle, kidney, liver and blub-
ber. Examinations of heavy metals were car-
ried out by the Hygienic Institute, Tórshavn
(Julshamn, Andersen, Ringdal and Mør-
køre, 1987; 1988; Julshamn, Andersen,
Svendsen, Ringdal and Egholm, 1989), while
a few persistent organochlorines were exa-
mined for the Faroese Fisheries Laboratory
(Bloch and Hoydal, 1987; Bloch, Hanusar-
dóttir, Davidsen and Kraul, 1987). Samples