Fróðskaparrit - 01.01.2007, Síða 165

BOTNDÝR í BLEYTBOTNI Á FØROYSKUM FIRÐUM
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had three replicates while KA05 had two
replicates. The diversity measures are in-
ternally very different and a summation of
all samples must be taken with caution.
Average species number for all samples
was 16 (1 - 38) and average abundance
was 240 (13 - 707). The average ratio be-
tween number of individuals and number
of species was 8.2 (2 -20.6). Species num-
bers are a little less compared with the
present investigation (Table 1) but both
abundance and N/S ratio were about the
same. The average Shannon diversity
index was 2.86 (0.28 - 3.65) and the aver-
age Pielou evenness index was 0.68 (0.46 -
0.84) which is a little below the values
found in this paper (table 1). The most
common species were Abra nitida, Thya-
sira sp., Mediomastus fragilis, Ampharete
baltica and Scalibregma inflatum.
Nørrevang (1988) analyzed samples
from Tórshavn harbour for macro fauna.
These samples are not fully comparable to
the other data mentioned in this paper be-
cause of a different sample size. The sam-
ples are also heavily impacted from harbor
activity and sewer outlets. From the refer-
ence station (about 20 m) Nørrevang iden-
tified Thyasira flexuosa, Ennucula tenuis,
Thyasira gouldii, Praxillella praetermissa,
and Cirratulis cirrata as the most common
species.
Josefson (2001) collected samples from
two soft bottom localities on the Faroese
shelf. Thirty-one grab samples were sam-
pled on Skeivibanki (south west of Suð-
uroy) and 15 grab samples were sampled
from a locality east of Suðuroy. All sam-
ples were 0.1 m2. It is not possible to see
exact numbers from the report but from the
fígures it is clear that the abundance is
about 25-30% lower than the other data in
mentioned in this paper. The total species
number was above 200 which is a little less
coinpared to the present investigation. The
distribution among the major taxonomic
groups seems to be a little different from
shallow water samples. The usual heavy
dominance by polychaetes is less pro-
nounced, about 40-50%. Molluscs and oth-
ers are about equal in total abundance.The
most abundant species on Skeivibanki
were Onchnesoma steenstrupi, Thyasira
ferruginea, Thysasira obsoleta, Caudo-
foveata sp. and Paramphinome jeffreysii
and the most abundant species east of
Suðuroy were Onchnesoma steenstrupi,
Golfingia sp., Lumbrineris sp., Paradiopa-
tra quadricuspis and Paramphinome jef-
freysii. Compared to the species from shal-
low waters none of the species are the
same.
Conclusion
The main purpose with this paper has been
to get a general picture of the macro fauna
composition in Faroese íjords and their
connected diversity measures. We investi-
gated species composition and found a
clear dominance of a few species (Scolop-
los armiger, Mediomastus fragilis, Thya-
sira flexuosa and Abra nitida) which is
only partly comparable with other investi-
gations, Nørrevang (1990), Jørgensen
(1993), Sakarisson (2000). We gave an
overview of species numbers, abundance,
abundance ratio, Shannon index, Pielou