Fróðskaparrit - 31.12.2000, Blaðsíða 87

NØRINGIN HJA TOSKINUM A LANDGRUNNINUM:
GÝTINGARØKI, EGGSPJAÐING OG FØÐIN HJA LARVUNUM
91
Hydrography
Temperature and salinity were measured
with a SeaBird CTD (model 911 plus) at 50
stations at the central and northern shelf re-
gions and slopes in 1995 during the period
10-14 April, and at 55 stations in 1999 dur-
ing the period 22-27 April. The salinity
was calibrated against water bottle sam-
ples, which were analysed on an Autosal
(model 8400A) salinometer.
Calanus fintnarchicus egg production
Egg production rates of Calanus fmmarchi-
cus were measured on three cruises: 25-29
April 1997 (50 stations), 17-25 April 1998
(73 stations), and 22-27 April 1999 (53 sta-
tions).
Live Calanus finmarchicus were collect-
ed with a WP2 net, equipped with a 1.1 litre
plastic bottle at the cod end. Healthy fe-
males were transferred into 1.1 litre incu-
bation chambers equipped with false bot-
toms (mesh size 400 pm) to separate eggs
from females. They were incubated at the
in situ temperature for 24 hours. Usually
10-12 females were incubated per station
and two females were held in each incuba-
tion chamber. After incubation, the cham-
ber content was filtered through a 30-pm
mesh net and the eggs counted.
Zooplankton
In April 1995 and 1999, cod eggs, cod lar-
vae, and C. fmmarchicus females were col-
lected for enumeration on the central and
northern shelf regions and slopes during
10-14 April 1995 (50 stations), and 22-27
April 1999 (55 stations). In 1995, the sam-
ples were collected with a WP2 net on ver-
tical hauls from a 50 m depth to the surface.
The net had a mesh size of 200 pm and a
towing speed of 0.3-0.5 m sec1. In April
1999, the samples were collected with a
Bongo net (diameter: 0.6 m) with a mesh
size of 200 pm. The net was slowly low-
ered down to approximately 50 m depth
and hauled up again to the surface, while
towing with a speed of about 2.5 knots.
The volumes filtered by the net were mea-
sured with a Hydro Bios flow meter, which
was mounted in the mouth of the net.
In May 1995, cod larvae were collected
with a MIK net. The circular opening had
a diameter of two metres. The mesh size
was 1.5 mm in the net and 0.5 mm at the
cod end. The net was lowered down to 10,
20, and 30 m depths while towing with a
speed of about 2.5 knots. The volumes fil-
tered by the net were measured with a Hy-
dro Bios flow meter, which was mounted in
the mouth of the net.
The zooplankton used for enumeration,
cod larval length measurements, and food
content investigation samples were pre-
served in 4% formaldehyde. In the labora-
tory, the larvae were identified and counted
and their gut content was identified. The
only cod eggs counted were those that were
so well developed that the characteristic
pigmentation pattern of cod embryos could
be recognised inside the eggs. Thus, the
cod egg enumeration only included those
embryos in the latest developmental stages.
To see whether or not the mean cod lar-
val length in April 1995 differed signifi-
cantly from that in April 1999, a Welsch’s
approximate T-test for two samples with
unequal variance was conducted.