414 
Fishery Bulletin 113(4) 
Table 2 
Results of the per-recruit analysis for wahoo ( Acanthocybium solandri ) in the southwest Pacific Ocean during 2008-2010 
under sensitivity (S1-S2) and fishery management scenarios (F1-F4). For each scenario, means and 95% confidence intervals 
(Cl) are given for current fishing mortality (F curren t) and 4 biological reference points: fishing mortality at which maximum 
yield per recruit is produced (F max ), fishing mortality at which the slope of the yield-per-recruit curve is 10% of the slope at 
the origin (Fq i), and fishing mortalities at which the spawning stock biomass per recruit (SSB/R) is 25% (FsSB25) and 40% 
(Fssb4o) °f th e SSB/R at F= 0. For each scenario, 100 iterations were conducted, and the percentage of iterations in which 
^current exceeded the reference point are given here for each scenario. 
Iterations in Iterations in 
Mean (95% Cl) 
Mean (95% Cl) 
which F curr ent 
exceeds target 
reference 
which F C uirent 
exceeds limit 
reference 
target reference points limit reference points points (%) points (%) 
Model 
scenario 
Mean (95% Cl) 
^current 
Eo.l 
F SSB40 
fmax 
F SSB25 
■^current 
>*0.1 
^current 
>*SSB40 
^current 
>F 
' 1 max 
-^current 
>*SSB25 
SI 
0.85 (0.82-0.89) 
0.96 (0.95-0.98) 
0.82 (0.78-0.85) 
2.22 (2.18-2.26) 
1.57 (1.48-1.65) 
18% 
53% 
0% 
4% 
S2 
0.80 (0.77-0.83) 
0.95 (0.94-0.96) 
0.81 (0.77-0.85) 
2.22 (2.18-2.26) 
1.55 (1.46-1.65) 
11% 
43% 
0% 
2% 
FI 
0.80 (0.77-0.83 
0.96 (0.95-0.98) 
0.87 (0.84-0.91) 
2.32 (2.27-2.37) 
1.72 (1.63-1.81) 
8% 
29% 
0% 
2% 
F2 
0.81 (0.78-0.84) 
1.03 (1.02-1.05) 
0.86(0.82-0.90) 
2.28 (2.24-2.32) 
1.65 (1.55-1.74) 
2% 
36% 
0% 
3% 
F3 
0.87 (0.83-0.90) 
1.07 (1.05-1.08) 
0.96 (0.92-0.99) 
2.46 (2.41-2.50) 
1.89(1.80-1.99) 
7% 
27% 
0% 
2% 
F4 
0.82 (0.80-0.85) 
1.00(0.99-1.02) 
0.93 (0.89-0.97) 
2.40 (2.36-2.44) 
1.94(1.82-2.05) 
9% 
32% 
0% 
0% 
for targeting large marlins (Istiophoridae) and light 
tackle and smaller terminal equipment used to specifi- 
cally target wahoo and similar-size mackerels and tu- 
nas. In addition to fishing gear, there are spatiotempo- 
ral differences in fishing effort between fishing sectors 
because the majority of fishing effort in the recreation- 
al fishery is expended during the day in more southern 
areas of the EEZ that are relatively close to the coast 
(Zischke et al., 2012). Therefore, differences in the size 
(and age) distributions of wahoo caught by commercial 
and recreational fisheries off eastern Australia may be 
due to the spatiotemporal differences in fishing areas 
between sectors (cf., Griffiths, 2010), rather than due 
to the selectivity of fishing gears, particularly if wahoo 
of different sizes or ages display different spatial dis- 
tributions. It is important to quantify fishery-specific 
selectivity probabilities for stock assessment and to 
understand how potential management changes might 
influence selectivity. 
Per-recruit analysis 
Dynamic pool models and virtual population analysis 
can be useful in situations (e.g., in developing fisheries) 
in which there are little historical catch and effort data 
(Gabriel and Mace, 1999). We provided an assessment 
of E current against a traditional limit reference point 
F max . However, because per-recruit models assume 
constant recruitment regardless of spawning stock 
size, estimates of F max may not be sufficient to ensure 
sustainability (Gabriel and Mace, 1999). We also esti- 
mated Fq i, a precautionary target reference point that 
may reduce the chance of overfishing and stock col- 
lapse, particularly in data-poor fisheries (Gulland and 
Boerema, 1973). Constant recruitment is assumed in a 
yield-per-recruit model and therefore is independent of 
variations in stock size, and recruitment overfishing is 
not able to be detected (Quinn and Deriso, 1999). We 
investigated recruitment overfishing by conducting an 
SBB/R analysis to assess E current against a limit refer- 
ence point of Fssb 25 and a target reference point of 
Fssb 40 (Goodyear, 1993). 
Current levels of F of wahoo in the southwest Pa- 
cific Ocean are below both limit (F max ) and target (Fq i) 
reference points for Y/R and the limit reference point 
(Fssb 25) f° r SSB/R, but they are similar to the target 
reference point (Essb 40^ for SSB/R (Table 2; Fig. 4). 
This finding indicates that, under current fishing prac- 
tices in commercial and recreational fisheries, wahoo 
may be at higher risk of recruitment overfishing than 
of growth overfishing — an observation that may be at- 
tributed to their fast growth and the low selectivity of 
juvenile fish by fisheries. Chale-Matsau et al. (1999) 
obtained similar results from a per-recruit analysis of 
the closely related Kanadi kingfish (Scomberomorus 
plurilineatus ) in South Africa; in that study, Fq j great- 
ly exceeded Egggso, and the authors suggested that 
FgsB 5 o be used as a biological reference point for that 
species as a safeguard to minimize the risk of recruit- 
ment overfishing. 
Sensitivity and management simulations 
The iterative approach to the per-recruit model allowed 
us to explore the likelihood that F current exceeded refer- 
ence points because of uncertainty in biological param- 
