French et al.: Strong relationship between catch of Hippoglossus hippoglossus and availability of habitat for juveniles 
121 
A 
B 
Haddock Box 
Atlantic 
Ocean 
7yf 
3L 
V * I 
3N / 
mA 
3 „ 
YSuitability Catch welaht 
Habitat suitability in relation 
to commercial catch 
Habitat suitability (scaled) 
Figure 4 
Relationship between commercial landings of adult Atlantic halibut (Hippoglossus hippoglossus) during 2010-2014 and 
suitability of habitat for juvenile Atlantic halibut in the northwest Atlantic Ocean. (A) The habitat-suitability layer, de¬ 
veloped with data from trawl surveys conducted during 2001-2013, overlaid with the map of catch weight from directed 
fisheries and bycatch landings from Butler and Coffen-Smout (2017). Fishery closures (FCs) include substantial conser¬ 
vation areas, marine protected areas, and nursery areas where fishing of Atlantic halibut is restricted or not permitted. 
(B) Histogram of habitat suitability versus commercial catch, showing the correspondence between landings and scaled 
habitat suitability values. 
0.0117, and for a few large residuals included in divi¬ 
sions 30 (below) and 4X (above). 
Discussion 
We provide evidence to support the nursery-size hy¬ 
pothesis, which states that the amount of juvenile hab¬ 
itat available is related to adult production (lies and 
Sinclair, 1982; Rijnsdorp et al., 1992; Gibson, 1994; 
Beverton, 1995; Sundblad et ah, 2014; Wilson et al., 
2016). We found a direct relationship between juvenile 
and fishery production within NAFO divisions, and 
a proportional relationship between suitable-habitat 
availability, and stock productivity. This is consistent 
with Wilson et al. (2016), who reported that recruit¬ 
ment among 5 flatfish species is limited by nursery 
area. They further found that juvenile abundance was 
related to suitable- habitat availability and, in turn, to 
the recruitment and abundance of adults. This result 
is also in agreement with tagging studies which consis¬ 
tently find that most tagged halibut are caught within 
200-km or less of the location of release (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 with more recent research that shows a 
high connectivity within patches of 227 km 2 (Boudreau 
et al., 2017) 
In this study, NAFO divisions that fall on the 1:1 
baseline of the relationship between the SH-based 
shares and abundance-based shares (survey data) can 
be considered to be meeting productivity expectations, 
whereas areas that fall above or below the baseline are 
exceeding or below expectations, respectively (see Fig. 
3). When compared with suitable-habitat availability, 
juvenile abundance in NAFO divisions 4Vs, 4W, and 
4X exceeded expectations, and fell short in NAFO divi¬ 
sions 5Y, 5Ze, 5Zw, 30, and 3Ps (Fig. 3A). This finding 
was consistent with previous research that revealed ar¬ 
eas with persistently high juvenile halibut abundance 
within the most productive NAFO divisions (Boudreau 
et al., 2017). Several factors may be contributing to 
such trends: variations in current and historic fishing 
pressures, migrations, prey availability, and environ¬ 
ment. Over the past few decades, fishery closures and 
no-take protected areas, for example, have been estab¬ 
lished throughout the northwest Atlantic (Butler and 
Coffen-Smout, 2017). In NAFO divisions 4Vs, 4W, and 
4X, the Haddock Box (nursery area), The Gully Ma¬ 
rine Protected Area, and the Northeast Channel Coral 
Conservation Area are substantial areas where trawl¬ 
ing and other fishing methods are highly limited or 
not permitted (Butler and Coffen-Smout, 2017). These 
areas also have high habitat-suitability values and are 
located in NAFO divisions where SH-based shares, 
juvenile abundance, and commercial landings are all 
high (Fig. 4). Closed areas may also explain why year- 
round closures on Georges Bank were followed by a 
dramatic increase in yellowtail flounder populations 
(Fogarty and Murawski, 2004). Closed areas on the 
