Voilen and Albert: Pelagic behavior of adult Remhardtius hippoglossoides 
469 
The cephalopod G. fabricii and the shrimps Pasiphaea 
spp. and P. borealis, all important prey species, may 
also have been encountered in the pelagic zone. Gonatus 
fabricii juveniles are distributed in the surface layers, 
living gradually deeper as they become older. As adults, 
G. fabricii are largely benthic at depths of 200—3000 m, 
performing upwards migrations at night (Kristensen, 
1983; Bjqrke, 2001). The mesopelagic shrimp Pasiphaea 
spp. is widely distributed in the Norwegian Sea and 
have the highest biomasses around 200-600 m depth 
(Dalpadado et al., 1998), whereas the shrimp P. bo- 
realis is known to perform diurnal vertical migrations, 
ascending in the water column in the evening and re- 
turning to the sea bottom in the morning (see Garcia, 
2007). 
In our study, Greenland halibut larger than 65 cm 
were the only ones feeding on demersal species such as 
eelpouts and other flatfish, but they also fed on epipe- 
lagic species such as herring. This finding differs from 
that of previous studies where the diet of large Green- 
land halibut was dominated by large groundfish, even 
when smaller size individuals fed heavily on smaller 
pelagic fish such as capelin (Yang and Livingston, 1988; 
Bowering and Lilly, 1992; Solmundsson, 2007). 
Because their pelagic distribution is supposed to be 
linked to foraging activity, the presence of suitable pe- 
lagic prey should be expected to influence the pelagic 
behavior of Greenland halibut. Important prey species 
such as cephalopods, capelin, and herring have strong 
seasonal migration patterns, and the abundance of these 
within any given geographic area is prone to seasonal 
and annual variations. One example would be herring, 
which was found to be prominent as prey on the conti- 
nental slope in October 1997, whereas in January 1998 
it was not identified as prey at all (Hovde, 2002). Heavy 
feeding on capelin, another migratory small pelagic 
species, has also been observed for Greenland halibut 
(Smidt, 1969; Bowering and Lilly, 1992). 
The vertical activity level of individual Greenland 
halibut showed a clear seasonal pattern, being highest 
in August-October. This is the period preceding the 
main spawning season, when mature Greenland halibut 
gather in the slope area (Albert et ah, 2001). It is also 
the period when annual surveys are made for popula- 
tion monitoring of the Northeast Arctic stock. 
Concluding remarks 
This is the first published account of adult Greenland 
halibut being caught in pelagic waters in considerable 
quantities in any part of its distribution area. In the 
present study, adult individuals were found to be widely 
distributed in the water column. Pelagic activity was 
related to fish size and dial and seasonal cycles and 
was influenced by variability in the distribution of prey 
species. Variations in availability to the survey trawl 
could be biasing the length- and sex-distribution of 
these catches as well as obscuring trends in population 
abundance and structure as derived from stock assess- 
ment. The methods used in our study are not suitable for 
quantifying pelagic behavior, but both diet composition 
and vertical activity from archival tags indicate that 
use of the pelagic zone may be significant. In order to 
improve abundance estimates, and thereby the basis 
for management decisions, it is important to develop 
methods to estimate the availability of adult Greenland 
halibut to bottom sampling trawl. 
Acknowledgments 
Four anonymous reviewers and the journal editor are 
thanked for valuable comments and suggestions on an 
earlier version of the manuscript. 
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