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Fishery Bulletin 116(2) 
cur at warm temperatures. Consequently, selection 
should favor differential optimal adult body sizes with 
respect to the temperature differences (Berrigan and 
Charnov, 1994; Atkinson, 1996). Moreover, several au¬ 
thors suggest that the temperature-size patterns may 
involve changes in the reaction norms of growth and 
maturation (Angilletta et al., 2004; Ohlberger, 2013). 
In relation to these studies, our results provide a clear 
evidence of the covariation of growth and maturation 
underlying the temperature effects on adult body sizes. 
Additionally, we show that some variation in these life- 
history traits (e.g., maturation) is likely to be chiefly 
plastic. 
Other sources of life-history variation 
Potentially, other factors may also contribute to the ob¬ 
served life-history variation in T. japonicus. For exam¬ 
ple, positively size-selective fishing may induce selec¬ 
tion for growth, favoring the genotypes associated with 
slower growth rates (Ricker, 1981; Conover and Munch, 
2002; Reznick and Ghalambor, 2005; Wang and Hook, 
2009; Enberg et al., 2012). Also, fishing-induced size 
truncation of adult demography (Hsieh et al., 2010) 
could potentially confound the patterns of differences 
in growth between the areas. The different length dis¬ 
tributions (Fig. 2) indicate higher mortality for fish 
along the SW than along the NE coast—a finding that 
is consistent with the higher fishing power of the ves¬ 
sels operating from Tsukuan in comparison with those 
from Kenfang. However, because estimates of fishing 
mortality for cutlassfish in Taiwan were unavailable, 
it remains unclear whether different fishing intensity 
accounts for the life-history variation in cutlassfish be¬ 
tween the areas. To enhance understanding of growth 
patterns for T. japonicus, we suggest identifying other 
relevant driving factors that affect growth of cutlass¬ 
fish (e.g., fishing and other biological interactions). 
We found that between-area variation in maturation 
schedules was more pronounced for males than females. 
In general, increasing body size tends to increase fit¬ 
ness more for female fish than for male fish (Bell, 1980; 
Gross and Sargent, 1985; Fleming and Gross, 1994). 
Consequently, selection may favor delayed maturation 
in females, compensating for the different growth rates 
between the areas. 
Our results indicate potential adaptive variation in 
adult growth rates and plastic variation in maturation 
of T. japonicus between 2 areas off Taiwan. The spatial 
patterns of adult growth rates and maturation follow 
the temperature gradient, indicating that temperature 
variability exerts an effect on the observed life-history 
patterns. Also, the different adult growth rates be¬ 
tween sexes are consistent with selection that favors 
sexual dimorphism with body size (Parker, 1992). 
Implications for fisheries management 
Adaptive and plastic variation in life-history traits are 
evidence of the complex effects of environmental and 
anthropogenic drivers on living organisms. Consequent¬ 
ly, it is critical to understand the processes that lead 
to variation in life-history characteristics in order to 
enhance the effectiveness of natural resource manage¬ 
ment. Subtropical and tropical fishes are under much 
pressure from both environmental changes and fisher¬ 
ies exploitation (Cheung et ah, 2010; Blanchard et al., 
2012). Our results provide essential information on how 
a subtropical fish responds to these effects, information 
(e.g., accounting for the area-specific life-history pat¬ 
terns and the regulation of fishing intensity) that can 
be incorporated in potential management plans. 
Our results indicate that there is a significant dif¬ 
ference in growth trajectories for T. japonicus from the 
2 primary fishing grounds in Taiwan. Such distinct 
growth patterns indicate the possible presence of dis¬ 
crete populations, and this result is in agreement with 
broad-scale patterns in mitochondrial DNA markers 
(Tzeng et ah, 2016). On the other hand, we did not 
find significant differences in the PMRNs, which might 
be expected to mirror observed genetic differences. A 
better understanding of the spatial scales of popula¬ 
tion differentiation and the roles of genetic and plastic 
variation in life-history traits of this important com¬ 
mercial species is clearly needed. 
There is increasing concern about the potential 
warming of ocean waters and the effects of this warm¬ 
ing on body size of various organisms, including com¬ 
mercially caught fish (Sheridan and Bickford, 2011; 
Baudron et al., 2014). Our findings contribute to an un¬ 
derstanding of the mechanisms underlying such warm¬ 
ing effects through the documentation of differences in 
growth rates of the T. japonicus that experience dif¬ 
ferent temperature regimes in the 2 sampling areas. 
Moreover, we suggest that the information on tempera¬ 
ture-size (life-history) relationships may be useful for 
forecasting changes in sizes of other subtropical fish 
species. 
Acknowledgments 
We are grateful to many laboratory members for their 
help with sampling and laboratory analysis. This re¬ 
search was funded by grants to H.-Y. Wang from the 
Fisheries Agency of Taiwan, 1Q2AS-1X.2.1-FA-F4 and 
103AS-11.2.1-FA-F2(7), and the Ministry of Science 
and Technology (MOST, Taiwan), NSC 102-26ll-M-002 
-001. M. Heino was funded by MOST grant 105-2811- 
M-002 -068. M. Heino also acknowledges financial sup¬ 
port from the University of Bergen and the Meltzer 
Foundation during his initial stay in Taiwan. 
Literature cited 
Angilletta, M. J., Jr., T. B. Steury, and M. W. Sears. 
2004. Temperature, growth rate, and body size in ecto- 
therms: fitting pieces of a life-history puzzle. Integr. 
Comp. Biol. 44:498-509. 
