Siwicke et al.: Spawning behavior of Reinhardtius hippoglossoides in the Bering Sea and Aleutian Islands 59 
generally coincided with data for males and females during 
January and February (Suppl. Fig. 1) (online only). Upon 
closer inspection, numerous spawning rises were identified, 
with 2 distinct patterns that mostly varied with sex: 1) a 
singular rise with a sharp ascent and descent for females 
and 2) more sporadic, often prolonged periods of rapid 
ascents and descents for males (Fig. 2). Maximum ascent 
rates ranged from 8.1 to 31.0 m/min, with maximum descent 
rates between 10.5 and 28.0 m/min (Table 1). 
Females 
Three of the 5 female Greenland halibut had spawning 
rises and were 84-88 cm FL at release; the 2 that did 
not were 68 and 71 cm FL at release. The females that 
exhibited spawning behavior did so for all winters at lib- 
erty (Fig. 3). The dates of the singular rises by females 
ranged from 12 January to 12 February, with individuals 
having almost exactly a 1-year interval between rises 
(Table 1). Individual females initiated spawning rises 
from relatively similar depths across years (Table 1). 
The shallowest depths recorded for females at the apexes 
of their rises ranged from 229 to 420 m, and the nar- 
rower estimates from interpolation were between 217 
and 326 m (Fig. 4). The elapsed time of singular rises 
ranged from 0.5 to 2.5 h. The duration of spawning rises 
generally lengthened with increases in the bottom depth 
Male (Tag no. 4122) 
0 
at which ascents were initiated. No consistent pattern 
for the time of day at which fish reached an apex was 
observed (Table 1). Recorded temperatures were 2.8— 
3.8°C before spawning rises and 3.7—4.1°C at the apex of 
ascents. Because the tags were internally implanted and 
the ascents and descents were steep, tag sensors were 
unlikely to have adjusted to the ambient water tempera- 
ture and the actual apex temperature was likely to have 
been warmer than tag data indicate. The movement of 
one fish (tag no. 386, with no spawning rises identified) 
is unique in that, during the winter, the fish moved to 
relatively shallow water, presumably to the continental 
shelf. 
Males 
All 6 male Greenland halibut exhibited spawning behavior 
during at least 1 winter for an average of 20 d. Four of these 
males were at liberty only for the winter of 2003-2004; 
for these males, spawning behavior occurred for 27-41 d 
between 2 January and 13 February (Table 1). One male 
was at liberty for 3 consecutive winters, and the data from 
its tag provides evidence of spawning behavior occurring 
in each year. In the third winter, this fish inhabited waters 
that were substantially deeper (depths of ~1200 m) than 
in the previous 2 winters (depths of 600—700 m), and it 
had a single, brief spawning rise to a depth of 508 m on 
17-18 January 2004 
0 
500; 
1000; 
1500+ 
_ 250; 
5004 
750; 
1000; 
J 
Jan 2004 
Time 
Jul 2003 Oct 2003 
Apr 2004 
17.0 17.5 18.0 18.5 19.0 
Time (day of year) 
17-18 January 2004 
Jul 2004 
Female (Tag no. 5282) 
0 ar 
2507 
5001 
750} 
1000+ 
~~ Jul 2003 Oct 2003 Jan 2004 
Time 
Apr 2004 
17.0 17.5 18.0 18.5 19.0 
Time (day of year) 
Jul 2004 
Figure 2 
Examples of 1 year of depth data for a male (top left) and female (bottom left) Greenland halibut (Reinhardtius hippoglossoi- 
des) tagged and released in June 2003 in the eastern Bering Sea. The vertical black dashed line in each left panel indicates the 
change in year from 2003 to 2004, and the black parts of lines indicate the timing of putative spawning. The right panels focus 
on depth data for 2 d (17 and 18 January 2004), and this period is highlighted by a vertical grey bar in each left panel, with the 
black parts of lines again indicating the timing of associated spawning. 
