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Fishery Bulletin 11 6(2) 
A commonly observed macroscale relationship be¬ 
tween growth and maturation with respect to variability 
in temperature, known as the “temperature-size rule,” is 
that organisms tend to grow faster, mature earlier, and 
reach smaller asymptotic sizes at warmer temperatures 
than at cooler temperatures (Atkinson, 1994; Arendt, 
2011; examples for fishes: Brunei and Dickey-Collas, 
2010; Matta et ah, 2016). Previous research indicates 
that this relationship may be due to the effect of tem¬ 
perature on asymptotic body sizes (e.g., a greater body 
size at cooler temperatures), which gives rise to adap¬ 
tive changes in energy allocation to reproduction and 
other competing needs (Berrigan and Charnov, 1994; 
Atkinson, 1996; Angilletta et ah, 2004; Hosono, 2011). 
Alternatively, nonadaptive temperature effects on meta¬ 
bolic rates may generate the same result (e.g., Angilletta 
et ah, 2004; Munch and Salinas, 2009). 
Theoretical models and concepts, such as the reac¬ 
tion norm model of maturation (Stearns and Koella, 
1986; Stearns, 1992), provide mechanisms for the ex¬ 
ploration of the plastic and adaptive processes of life- 
history traits. By definition, the maturation reaction 
norms represent genetically coded traits, the changes 
of which are evolutionarily “optimized” through chang¬ 
es in mortality and growth rates (Stearns and Koella, 
1986; Stearns, 1992). The probabilistic maturation reac¬ 
tion norm (PMRN) approach (Heino et ah, 2002; Dieck- 
mann and Heino, 2007; Heino and Dieckmann, 2008) 
builds on the deterministic concept of maturation reac¬ 
tion norms by Stearns and Koella (1986). The PMRN 
approach involves statistically accounting for the major 
sources of plastic effects due to growth and survival 
and quantifying the remaining variation in maturation 
as more likely to represent adaptive genetic variation 
(Heino et al., 2002). Although this approach also is crit¬ 
icized (e.g., Kraak, 2007), several authors have applied 
this method to infer potential evolutionary changes in 
maturation for exploited fish species (e.g., Atlantic cod 
[Gadus morhua], Olsen et ah, 2005; smallmouth bass 
[Micropterus dolomieu ], Dunlop et ah, 2005; and lake 
whitefish [Coregonus clupeaformis ], Wang et ah, 2008; 
reviewed by Heino et ah, 2015). Furthermore, a few 
studies have attempted to account for other sources of 
plastic effects in the PMRN model, such as body condi¬ 
tion (Grift et ah, 2007; Uusi-Heikkila et ah, 2011) and 
social cue (e.g., presence of fish of same or opposite sex; 
Diaz Pauli and Heino, 2013). 
Cutlassfish (some of which are also known as hair- 
tails), including several Trichiurus species, are an im¬ 
portant fisheries resource in the subtropical West Pa¬ 
cific (He et ah, 2014; Wang et ah, 2017). However, reli¬ 
able species identification is difficult without the use of 
genetic methods, and in the FAO fisheries “capture pro¬ 
duction statistics,” the catches of multiple cutlassfish 
species are lumped into a value for one nominal spe¬ 
cies, Trichiurus lepturus (Hsu et ah, 2009; FAO, 2014). 
For this reason, and because of the lack of fishery stock 
assessments and regular surveys, the population ecol¬ 
ogy of individual Trichiurus species is poorly known. 
Nonetheless, T. japonicus is likely a dominant species 
that contributes substantially to the coastal catch in 
this region (i.e., this species accounts for 40-100% of 
the total cutlassfish catch; Wang et ah, 2017). Also, 
this cutlassfish is an important predatory fish in the 
subtropical Pacific and, moreover, has a year-round 
spawning behavior (Liu et ah, 2009; Shih et ah, 2011). 
In this study, we focused on investigating growth 
and maturation patterns for T. japonicus along the 
Taiwan coast in the northwestern Pacific (Fig. 1). In 
Taiwan, 2 primary fishing grounds are located along 
the northeast (NE) and southwest (SW) coasts, and to¬ 
gether they account for about 30% (range: 24-40%) of 
total annual catch of cutlassfish (based on 2003-2014 
data from the Taiwan Fisheries Agency 2 ). The results 
of a previous study indicate that these fishing grounds 
may represent distinct populations of T. japonicus (Tz- 
eng et ah, 2016). In addition, environmental and fish¬ 
ing conditions vary between these fishing grounds. 
Temperatures are lower along the NE coast than along 
the SW coast, in particular in winter. For example, 
the sea-surface temperatures (SSTs) are 19.2-24.6°C 
in winter (December-February) and 26.3-29.1°C in 
summer along the NE coast (June-August), and SSTs 
are 22.5-24.9°C in winter and 29.0-30.4°C in sum¬ 
mer along the SW coast (Fig. 1) (also see Jan et ah, 
2002). The primary fisheries on both fishing grounds 
are pursued by using pair trawlers, but because of a 
lack of stock assessments, the fishing intensity is un¬ 
known. However, the number and size of trawlers were 
greater on the SW coast (282 boats, primary boat size 
of 50-100 metric tons) than along the NE coast (232 
boats, primary boat size of 20-50 metric tons; Taiwan 
Fisheries Agency 3 ), and therefore there is a higher ex¬ 
ploitation pressure in the SW than on the NE coast. 
We hypothesize that the habitat or fisheries conditions 
have led to faster growth rates and earlier maturation 
patterns of T. japonicus along the SW coast than along 
NE coast. 
Our objective was to describe growth and matura¬ 
tion of T. japonicus for the 2 fishing grounds and to 
infer potential adaptive-versus-plastic variation in the 
life-history traits of this species. Because the popula¬ 
tions of T. japonicus at these 2 fishing grounds likely 
are distinct (Tzeng et al., 2016), some variation in 
adaptive traits for these populations may arise as a 
consequence of their genetic variability. We estimated 
the PMRNs to evaluate potential adaptive variation 
in maturation schedules and explored plastic changes 
in maturation schedules that are due to variations 
in growth. Also, we explored the covariation between 
growth and maturation in relation to habitat differ¬ 
ences of the two areas. 
2 Taiwan Fisheries Agency. 2015. Fisheries statistical year¬ 
book: Taiwan, Kinmen and Matsu area 2014. Fish. Agency, 
Counc. Agric., Executive Yuan, Taiwan. [Available from 
website.) 
3 Taiwan Fisheries Agency. 2016. Fisheries statistical year¬ 
book: Taiwan, Kinmen and Matsu area 2015. Fish. Agency, 
Counc. Agric., Executive Yuan, Taiwan. [Available from web¬ 
site.] 
