Vollen and Albert: Pelagic behavior of adult Reinhardtius hippoglossoides 
459 
greater than 1000 m, a drifting ver- 
tical longline with no anchor was 
used. Soak time ranged from 3 to 
33 hours. During the main survey 
in August 2005 mean soak time was 
12.6 (±6.1 standard deviation [SD]) 
hours. 
The vertical longlines were rigged 
to optimize the vertical stability. 
During the main survey in August 
2005 the anchor settled on the sea- 
floor within 10-15 minutes, and the 
vertical longline settled at the proper 
depth after about 30 minutes. Once 
settled, depth of the lowest hook 
typically had a 2SD of 15-45 m. 
Stability increased for hooks high- 
er up in the water column (Fig. 2). 
With the exception of the few deep- 
est hooks, which at some settings 
may have been close to the seabed 
for a few minutes, hooks were at a 
pelagic depth throughout the soak 
time. During earlier cruises the 
vertical stability was more variable, 
with 2SD ranging from 2 to 150 m. 
The hauling process was completed 
in approximately 30 minutes in all 
experimental periods. 
All fish caught on vertical long- 
lines were classified to species, and the catch 
depth D c was calculated as follows: 
D= D,+(D, - D.)HJH mn „, 
100 
200 
300 
400 
500 
600 - 
700 
Surface 
Anchor (bottom) 
*- r- <M 
Time 
Figure 2 
Depth profile of a vertical longline from August 2005. One archival tag was 
attached to the anchor and another three to the vertical longline at differ- 
ent intervals. Depths were recorded every 3 minutes from time of setting 
to hauling. Vertical movements of this longline were larger than those for 
most longlines from August 2005 (2 standard deviations of mean depth for 
the lowest hook=51 m, versus 15-45 m for most August 2005 longlines). 
where D h and D t 
H„ = 
H„ 
= the mean depths of the 
highest and lowest hook 
as measured by archival 
tags; 
the hook number of the 
catch; and 
the total number of hooks 
on the hooked section. 
10 
15 
Soak time (h) 
Figure 3 
20 
25 
30 
Observed relationship between mean catch (in number) of Green- 
land halibut (Reinhardtius hippoglossoides) and soak time (1-hour 
groups) for vertical longlines. n = 221. The solid line represents the 
saturation model used. All means were based on groups of nine or 
more vertical longlines from August 2005. 
For all Greenland halibut a standard bi- 
ological sampling was performed (length, 
weight, sex, maturity, and stomach fullness). 
Stomachs with contents were frozen and an- 
alyzed in the laboratory. Prey items were 
counted, weighed, and determined to the 
lowest possible taxonomic level. The diges- 
tion status was noted according to a five-point scale: 1) 
fresh, 2) digestion just started, 3) moderately digested, 
4) highly digested, and 5) digestion almost complete. 
Longline bait was easily recognized and excluded from 
the analysis. 
According to data from August 2005, the catch rate 
of vertical longlines increased with soak time until 
saturation was reached after approximately 15 hours 
(Fig. 3). Fishing effort, E :jk , generated by a single ver- 
tical longline k during setting time T k within a given 
combination of fishing depth interval i and bottom depth 
interval j was thus defined as 
Eijk ~ T 'k x Hij k /100, 
where T' k = T k if T k < 15 hours; 
T' k = 15 hours if T k > 15 hours; and 
H ijk = the number of hooks. 
