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Fishery Bulletin 120(1) 
every few days over a period of weeks, can be identified in 
archival tag data. Spawning rises have been inferred for 2 
batch-spawning species, the Pacific halibut (Hippoglossus 
stenolepis) and the Atlantic halibut (H. hippoglossus), by 
using archival tags. 
Although female halibut are expected to have multiple 
spawning rises separated by at least 2 days, during which 
time batches of ova are hydrated (St-Pierre, 1984; Finn 
et al., 2002), male halibut are limited only by mating oppor- 
tunities, resulting in a pattern in which spawning rises are 
more variable and frequent. In previous studies, data from 
archival tags was used to reveal spawning rises in females 
(e.g., one Pacific halibut rose 7 times in 3 weeks), and the 
authors also hypothesized that male spawning behavior 
had a more frequent and variable rise pattern, although 
sex was not identified (Seitz et al., 2005; Loher and Seitz, 
2008). Similar patterns of spawning behavior of Atlantic 
halibut have been discerned in archival tag data with sex 
determined: female spawning has been characterized by 
4-6 rises over a period of 10-17 d, and males have been 
reported to have more sporadic rises over a protracted 
period (Murphy et al., 2017). 
The Greenland halibut (Reinhardtius hippoglossoides), 
also known as the Greenland turbot, is a close relative to 
the Pacific and Atlantic halibut (Vinnikov et al., 2018) and is 
a commercially important deepwater flatfish species found 
in the North Atlantic, North Pacific, and Arctic Oceans. 
This species can reach a size of up to 120 cm in fork length 
(FL), and females become mature at 60—70 cm FL (Cooper 
et al., 2007). Adult Greenland halibut have been found at 
depths greater than 1500 m and in waters with tempera- 
tures from 0°C to 4°C (Peklova et al., 2012; Siwicke and 
Coutré, 2020). Archival tag data from other studies indicate 
that Greenland halibut exhibit much vertical activity (Boje 
et al., 2014; Siwicke and Coutré, 2020) and can spend up to 
a quarter of their time in the pelagic environment (Albert 
et al., 2012). This species carries 2 cohorts of vitellogenic 
oocytes that are easily separated by their relative diam- 
eters, large and small (Kennedy et al., 2011). Interpreta- 
tions of this trait for Greenland halibut have evolved (e.g., 
Fedorov, 1968; Rideout et al., 1999; Gundersen et al., 2000; 
Junquera et al., 2003), but the most recent understanding 
is that oocytes take more than 1 year to complete vitellogen- 
esis, 2 cohorts of oocytes are present, with the large cohort 
spawned in the current year and the small cohort spawned 
in the following year (Kennedy et al., 2011; Rideout et al., 
2012). This reproductive trait has been found in other cold- 
water fish species (e.g., Everson, 1994). 
One basic aspect of reproduction of Greenland halibut that 
is uncertain is whether females are batch or total spawners 
(Stene et al., 1999; Kennedy et al., 2009). Female Greenland 
halibut are often caught in a prespawning or postspawning 
stage, and ripe or running females are rare. A single run- 
ning female readily released all of her ovulated eggs when 
artificially spawned (Stene et al., 1999), and another female 
Greenland halibut released a single batch of eggs over the 
course of a year in a laboratory (Dominguez-Petit et al., 
2013); both of these outcomes indicate that the species is a 
total spawner. When ripe females have been caught during 
longline surveys near Greenland, all oocytes were hydrated 
(although it was not stated whether this finding was only 
for the large cohort of oocytes), indicating that Greenland 
halibut spawn a single batch in the wild (Gundersen et al., 
2013). The term total spawner can be used to describe a 
Greenland halibut that releases eggs once in a year (Murua 
and Saborido-Rey, 2003). 
Knowledge of the timing and location (spatial and depth) 
of spawning is important for understanding stock struc- 
ture and dynamics (i.e., egg-larval drift and migrations), 
basic information used in stock assessment and fisheries 
management. For Greenland halibut, these characteris- 
tics appear to vary by region and are poorly understood. 
Spawning activity of Greenland halibut inferred from 
gonadosomatic index analyses indicates that spawning 
occurs along the continental slope from November through 
January (Albert et al., 2001). Larval distributions indi- 
cate that this species spawns at depths between 800 and 
1000 m from December through April (Smidt, 1969). Sere- 
bryakov et al. (1992) determined that spawning occurs at 
depths between 1000 and 1500 m, using the presence of 
larvae at these depths. The majority of the spawning of 
Greenland halibut in the eastern Bering Sea is assumed 
to occur deep on the slope (Alton et al., 1988) and between 
October and March (October—December, Musienko, 1970; 
February—March, Bulatov, 1983; and December—January, 
Sohn et al., 2010). Archival tag data from another study 
indicate that this stock does move to deeper waters along 
the continental slope during winter, a shift that is pre- 
sumed to be from feeding to spawning grounds (Siwicke 
and Coutré, 2020). In captivity, spawning has occurred 
mostly from January through March in consecutive years 
(Dominguez-Petit et al., 2013). It is difficult to know what 
effect the laboratory conditions had on reproduction. 
The depth at which eggs are released influences egg 
dispersal (currents) and development time (temperature). 
Both development of the embryo and timing of hatching 
are dependent upon the surrounding water temperature 
(Dominguez-Petit et al., 2013). It is believed that, in the 
Bering Sea, spawning occurs in deep submarine canyons 
and eggs are advected up and onto the nursery grounds of 
the continental shelf (Sohn et al., 2010; Duffy-Anderson 
et al., 2013). The accuracy of these assumptions will influ- 
ence the accuracy of estimated development time and 
hatch date. For example, if an egg was in water that is 
warmer than assumed, the development time would be 
shortened, the back-calculated hatch date would be later 
in the year, and the time for egg dispersal by currents 
would be shortened. Additionally, if the depth at which 
eggs are released is incorrect and if current speed varies 
by depth, estimates of dispersal distance of eggs will also 
be affected. 
If spawning is identifiable in archival tag data, this 
method can be useful for corroborating estimates of size at 
maturity and other characteristics from stock assessments. 
Currently, the assessment of the Bering Sea—Aleutian 
Islands (BSAI) Greenland halibut stock uses a logistic 
relationship of maturity and size, with the length at 50% 
maturity (L;,) set at 60 cm (2% at 50 cm and 98% at 70 cm) 
