Fróðskaparrit - 31.12.2000, Blaðsíða 166

170
INDIVIDUAL ANALYSES OF MERCURY AND ORGANOCHLORINES
IN MARINE MAMMALS FORM THE FAROE ISLANDS
concentration of Sum DDT is similar for
the adult male groups of the two whale
species. In both whale species o,p’-DDE
were found in the lowest concentration of
the six DDT isomers analysed.
Of the toxaphene compounds, the parlars
26, 32, 50, 62, and 69 were analysed, but of
these parlars 32 and 69 were not detected in
any sample. The parlars 26 (T2) and 50
(T12), the former an octa- and the latter a
nonachlorbomane, are both present in tech-
nical toxaphene in small percentages (less
than 1%), but known to be persistent in ma-
rine biota (Buser and Miiller, 1993; Vetter
et al., 1993). In a study of biotransforma-
tion in harbour seals, it was found that the
chlorinated bornanes 32 and 62 were fully
metabolised (Boon et al., 1996).
The concentration of toxaphene in the
groups of grey seals is shown with those for
white-sided dolphins in Table 13 and plot-
ted vs. age (Fig. 13). As with the grey
seals, there were no measurable concentra-
tions of Parlars 32 and 69 in the white-sided
dolphins. Parlar 62, which was only found
in one adult male grey seal (the 21 year
old), is abundant in the white-sided dol-
phins and this correlates well with the me-
tabolism observed to occur in white-beaked
dolphins (Boon et al, 1996). What is most
remarkable about the toxaphene results is
perhaps that the mean value for Sum
toxaphene for the adult females is merely a
factor of one-tenth that of the mean for all
the white-sided dolphins (Fig. 14).
The results of the toxaphene analyses in
pilot whales are shown in Table 14 and Fig.
15. The two highest toxaphene concentra-
tions in both pods, equal to 13 and 12
mg/kg lipid, were found in juvenile fe-
males, but Fig. 15 shows that also among
the males, the juveniles carry relatively
high concentrations.
Discussion
The results of this study reveal that essen-
tially the concentration of the organochlo-
rines analysed was always lowest in the
adult females of a species. The one excep-
tion was that of the grey seals: the adult fe-
male group had higher concentrations than
the juvenile females of some of the POPs
like Mirex, hexachlorobenzene, and a-
chlordane. An explanation for this may be
that the juvenile female seals on average
are very young, only two years, whereas the
average age of the juvenile female pilot
whales is probably around four years.
The Tórshavn 24 September 1997 juve-
nile pilot whales were in general larger than
those of the Sandavágur pod. The average
body length of the young females and
males of the former pod was 277 cm and
406 cm, respectively. The females and
males of the latter pod were 270 and 372
cm, respectively. The mean body length of
the 54 juvenile females and 104 males
analysed in the full screening was 297 cm
and 387 cm, respectively (Dam and Bloch,
2000).
The present study confirms the results
from an earlier study of pilot whales and
grey seals (Larsen and Dam, 1999) in
which the concentration of CB 153 was
found to be higher in adult male seals than
in adult pilot whale males. The concentra-
tion in the adult females and young were,
however, lower in the seals than in the