• growth pattern;
  • ocean period;
  • Pacific salmon;
  • scale;
  • smolt body size

This study compared the growth rates of female masu salmon Oncorhynchus masou, who possessed a male-specific gene marker, the growth hormone pseudogene (GHp), and normal females, as estimated from their scale growth. There was a difference between the growth rates of GHp-positive females and those of normal females of the same age during the ocean period, although their growth rates during the river period were similar. These results suggest that GHp-positive salmonid females exhibit male-like characteristics such as reduced feeding activity during the ocean period, which depresses their growth.