112 
Fishery Bulletin 11 6(2) 
Map of the range of the stock of Atlantic halibut (Hippoglossus hippoglossus) on the Scotian Shelf and 
southern Grand Banks, and areas of interest for this study in which the relationship between commer¬ 
cial catch of adult Atlantic halibut and availability of suitable habitat for juveniles in the northwest At¬ 
lantic Ocean was examined (by using data from surveys conducted during 2001-2013 and maximum en¬ 
tropy modeling). Thin, solid lines indicate the borders of North Atlantic Fisheries Organization (NAFO) 
divisions, within and outside of Canada’s Exclusive Economic Zone (EEZ). 
Informal reports from both the U.S. and French fish¬ 
ing industries suggest that halibut are becoming more 
abundant within their jurisdictions and fishery man¬ 
agers have expressed renewed commercial interest in 
the Atlantic halibut fishery. However, there is limited 
ecological information to support transnational discus¬ 
sions concerning shared allocations of catch (Bigelow 
and Schroeder, 1953; McCracken, 1958; Stobo et ah, 
1988; Neilson et ah, 1993; Cargnelli et ah, 1999). A 
major challenge facing Atlantic halibut research is a 
lack of data on the past and present distributions and 
abundances of this species. Historically this species be¬ 
came of commercial interest only after decades as dis¬ 
carded bycatch in the cod (Gadus morhua ) fishery and 
was quickly exploited to a critical state in the 1850s 
(Grasso, 2008). Before the establishment of a fishery- 
independent index of abundance (1970s), Atlantic hali¬ 
but were heavily impacted by fishing activity for other 
groundfish, and the current period of high recruitment 
especially in Canada, is a relative measure compared 
with abundances during the regional groundfish mora¬ 
torium of the early 1990s (Collette and Klein-MacPhee, 
2002; Grasso, 2008). 
Atlantic halibut is the largest of all flatfish (Big¬ 
elow and Schroeder, 1953; Collette and Klein-MacPhee, 
2002). It is long lived and sexually dimorphic; males 
reach maturity at smaller sizes (77-80 cm in total 
length [TL]) than females (103-125 cm TL) (Bowering, 
1986; Trumble et al., 1994; Sigourney et al., 2006). 
This species is capable of long-distanced migrations, 
but the majority of tagged fish are recaptured locally 
(McCracken, 1958; Jensen and Wise, 1961; Neilson et 
al. 5 ; Stobo et al., 1988; Kanwit, 2007; den Heyer et 
al., 2012; Seitz et al., 2016) and therefore may reflect 
populations with both resident and migratory indi¬ 
viduals (e.g. Nielsen and Seitz, 2017) or seasonal mi¬ 
grations to putative spawning areas (e.g., Le Bris et 
al., 2017). This finding indicates lower levels of mix¬ 
ing than those under the long-held presumption that 
the stock is a large, interbreeding population (Seitz et 
al., 2016). The tendency to remain stationary until the 
age of 4-6 years and a homing response to spawning 
grounds have been observed among Atlantic halibut 
in Norway (Godp and Haug, 1988). In the Northwest 
Atlantic, a lack of known spawning-site location and 
egg or larvae data has meant that distributions of this 
species during the earliest life history stages are un¬ 
known. Moreover, because current standardized trawl 
surveys are limited by depth, they lead to uncertain¬ 
ties in determining halibut presence and activities in 
deeper waters. Studies with electronic tags to elucidate 
northwest migration patterns and spawning locations 
of Atlantic halibut (e.g. Armsworthy et al., 2014; Seitz 
et al., 2016; Murphy et al., 2017; Le Bris et al., 2017) 
will ultimately improve our ability to define and man¬ 
age halibut stocks. However, owing to growing commer¬ 
cial interests, there is an immediate need for scientific 
information to support management decisions. 
5 Neilson, J. D., W. R. Bowering, and A. Frechet. 1987. 
Management Concerns for Atlantic halibut (Hippohlossus 
hippoglossus ) in the Canadian North Atlantic. CAFSAC 
Res. Doc. 87/73, 23 p. [Available from website.] 
