Trans-Atlantic Study of Calanus: Calanus in different light and predatory regimes

The objective of this subtask of the Trans-Atlantic Study of Calanus programme
was to assess mortality risk of Calanus with respect to visual predators (fish)
along a latitudinal gradient in the Norwegian Sea and how this impacts plankton
vertical distribution and life history traits.

Studies on zooplankton vertical distribution will be done by MOCNESS, Multinet,
WP2 net, Juday net or by pump. Fish will be assessed acoustically (SIMRAD EK
500, 38 Khz), and by Harstad trawl. Studies on the impact of midnight sun will
be performed on cruises with "Jan Mayen" in May and July 1996, and on a cruise
with "Haakon "Mosby" from waters off Bergen to north of the polar circle the
summer of 1997. Studies on migration and feeding by mesopelagic fish will be
carried out along the same transects. Egg production measurements (by
incubation) will be done along the same transect. Animals for gut fluorescence
measurements will be sampled day and night. Size fractionated chlorophyll
measurements will be performed to assess field feeding conditions. Studies on
the vertical distribution of Calanus along a latitudinal gradient during winter
will be done in cooperation with the Institute of Marine Research, Bergen,
using their research vessels. The flexibility in selection of overwintering
habitat will also be addressed by comparative studies the vertical distribution
of Calanus in fjords with, and without mesopelagic fish. Two-day cruises with
the research vessel "Hans Brattstroem" will be carried out each month (budget
permitting) from the summer 1996 to spring 1997, complemented by cruises with
RV "Haakon Mosby" spanning several days. We will synthesize data on herring and
mackerel abundance, distribution and feeding to get a rough estimate on their
potential pedation impact on Calanus.

Cruises:

Jan 4-11, 1996 RV Hakon Mosby
Feb 10-17, 1996 RV Hakon Mosby
Nov 6-10, 1996 RV Hakon Mosby
Jun 19-Jul 16, 1997 RV Hakon Mosby