Vollen and Albert: Pelagic behavior of adult Reinhardtius hippog/ossoides 
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8 47 70 35 22 5 1 
Catch depth (m) 
80 
70 
60 
50 
40 
400 600 800 1000 1200 1400 
Bottom depth (m) 
0 200 400 600 800 
Distance from bottom (m) 
Figure 5 
Line plot of sex composition and box plot of length of Greenland halibut ( Reinhardtius hippoglos- 
soides) caught on vertical longlines, by catch depth, bottom depth, and catch depth in distance from 
the bottom (all in 100-m intervals). Data are from August 2005. The number of individuals is given 
above plots. The plots show median, inter quartile range, upper and lower fence, and outliers as 
defined in SYSTAT 11 (SYSTAT Software Inc., San Jose, CA). Note that % males and % females 
add up to 100%. 
time than during the day, indicating that 
many of the Greenland halibut in the upper 
300 m during night may migrate to deeper 
waters during the day. The higher number of 
observations early in the day in the 300-500 
m depth zone, and later in the day at depths 
below 500 m support this (Fig. 7). The verti- 
cal activity increased and the diurnal signal 
weakened with increasing depth. The num- 
ber of recaptures was not considered high 
enough to warrant analyses of individual and 
seasonal differences in the diurnal activity 
pattern. 
The larger-scale time-variability is illus- 
trated in Figure 8, which shows the depth 
trajectory of five tagged fish, together repre- 
senting the typical pattern seen in all tags. 
In most cases periods of high vertical activity 
began with a sudden descent to much deeper 
depths than those occupied at any time dur- 
ing the periods of low vertical activity. This 
pattern is clearly apparent from examples Al, 
A2, and Cl in Figure 8, where periods of low 
vertical activity at depth less than 500 m sud- 
denly changed to periods of high-frequency 
changes in depth between 500 and 800 m. 
Example A3 shows a trajectory from a tag 
that stopped recording after a sudden descent 
to depths greater than 1000 m, which is the 
depth limit of the tag. This cessation in re- 
cording happened to three of the 25 recovered 
time series. 
The degree of high vertical swimming activ- 
ity (VA) varied throughout the year (Fig. 9). 
The proportion of days with high vertical ac- 
tivity was greatest during August-October 
and least in January and February. 
15 
10 
5 
15 
10 
C 
<D 
O 
<5 
5 
15 
10 
5 
0 
20 30 40 50 60 70 80 90 100 
Length 
Figure 6 
Length-frequency distribution (2-cm length groups) of female and 
male Greenland halibut ( Reinhardtius hippoglossoides) caught by 
vertical longlines, conventional demersal longlines, and demersal 
trawl. Data are from August 2005. Bottom depths covered were 
451-1235 m for vertical longlines, 349-932 m for demersal long- 
lines, and 433-1325 m for trawl. 
