140 
Fishery Bulletin 120(2) 
target bigeye tuna at depths between 100 and 400 m, with 
a median depth of 250 m (Bigelow et al., 2006; Woodworth- 
Jefcoats et al., 2018). This gear has a mainline that spans 
an average of 65 km, with an average total number of 
hooks of 1700 and with 27 hooks per float (Bigelow et al., 
2006). The hooks are baited with either Pacific saury 
(Cololabis saira) or Pacific sardine (Sardinops sagax) and 
generally are set in the morning and hauled in the after- 
noon or evening (Bigelow et al., 2006). Shallow-set gear is 
used primarily to target swordfish at depths between 30 
and 90 m. The mainlines of this gear span 75 km, with a 
total of 700-1000 hooks and roughly 5 hooks per float. 
The hooks are baited with Pacific chub mackerel (Scomber 
japonicus) and generally are set at night when swordfish 
are closer to the surface (Dewar et al., 2011). In 2019, 
there were an estimated 22 vessels using shallow-set gear 
and an estimated 143 vessels using deep-set gear in the 
North Pacific Ocean (PIFSC’). 
_ 1996-2013 
No. of hooks set 
5,000,000 
4,000,000 
3,000,000 
* 2,000,000 
1,000,000 
0 
— | 
1000 2000 km 
146eW 120W 
Rao 
- U 
CO-=NWAGOC 
m 
N 
0 1000 2000 km ® 0°. ; 0 
Prior to analyses, the data were filtered and separated 
into deep and shallow sets by using the methods of Bigelow 
et al. (2006), with deep-set data containing sets with 15 or 
more hooks per float and shallow-set data containing sets 
with less than 15 hooks per float. However, >95% of deep 
sets had 19-32 hooks per float and 500-3500 hooks per 
set, and >95% of shallow sets had 4-8 hooks per float and 
500-1500 hooks per set. We therefore excluded sets outside 
these ranges, to focus our analyses on typical deep-set and 
shallow-set gear configurations. Data were removed from 
analyses if soak times (the duration over which the fishing 
gear is completely submerged) were outside of reasonable 
bounds based on knowledge of fishery operations: 2-8 h 
for deep sets and 2-10 h for shallow sets. Records were 
also removed if they were outside the general geographic 
range of each fishery (deep sets: 180—125°W, 0—45°N; shal- 
low sets: 180—125°W, 15—45°N). All data from 1995 did not 
meet the filtration criteria and were removed, effectively 
BOEHZ01S 
| 
| 
| 
| 
N 
—i | | 
0 1000 2000 km ® 
—-420°~W 
— 140°W 
N 
_— | 
1000 2000 km &® 
140°W 120°W 
| E ; : . 
180° 160°W 140°W 120°W 
Figure 1 
Map of the (A and B) average annual effort, measured as number of hooks, and (C and D) aggregate nominal catch per unit of 
effort (CPUE), measured as number of individuals per 1000 hooks, for opah (Lampris spp.) caught by the U.S. deep-set longline 
fishery during 1996-2013 and 2014—2018 in the central and eastern North Pacific Ocean. Logbook data are binned into 5°-by-5° 
blocks, and blocks with data from less than 3 vessels are not shown to maintain confidentiality. 
