We  investigate d  va ria- t ion  in  growth  and   maturation  in   response  to  1)  spatial  variation  in   climate   and   2)  exploitation   of   the   subtropical   cutlassfish Trichiurus  japonicus ,  an  important  fishery  species  whose  population  ecology  i s   virtually  unknown .  Individuals  of   this  cutlassfish  species  were  sampled  monthly  at  2  primary  landing   sites:  Kengfang,  in  northeast  (NE)   Taiwan,  and  Tsukuan,   in  southwest   (SW )  Taiwan,  during  2013–2015.   Habitat  temperatures  were  about   1–4°C  lower  at   the  NE  site  t han  at   the  SW  site,  and  the  length  at  age   of   adult   fish  had  a n  inverse  pattern   with  temperature   (NE  lengths  > SW   lengths  at  age).  The  probabilistic   maturation  reaction  norms  did  not   differ significantly between the 2 areas, but ages and lengths a t maturation  were  higher  for  males  from  NE   than  for  males  from  SW.  Differences   in  asymptotic  lengths  (NE>SW)  and   growth coefficients (NE<SW), tog eth- er with narrower length distribution  at  the  SW  site  than  at  the  NE  site,   indicate  potentially  different  mortality  between  the  areas  (NE<SW).   These  results  indicate  plastic   variation  in  maturation  and   potentially   adaptive variation in growth for  this  species that are related to the differences  in  temperature  and  mortality   between the areas, although reliable  proxies  for   mortality  are   lacking.   The  observed  life-history  variation   was  consistent  with  the  tem perature–size  rule  that  organisms  tend   to  grow  faster,  mature  earlier,  and   reach   smal ler  asymptotic  sizes  at   warmer  temperatures  and  may  indicate  an  adaptive  divergence  of  cutlassfish populati