Age, Growth and Population Structure Analyses of the Berryteuthis magister shevtsovi in the Japan Sea by Statolith Microstructure

Berryteuthis magister shevtsovi is a new subspecies in the Japan Sea, and thus, little is known about its fisheries biology, especially age and population structure. Based on the 296 samples collected by the Chinese commercial jigging vessel in December 2018 in the Japan Sea. The age, growth, and population structure of B. magister shevtsovi were studied based on the microstructure of the statolith. The results indicated that the range of mantle length (ML) was 90–148 mm for females and 94–141 mm for males, the body weight (BW) ranged from 49 to 116 g and 38 to 110 g for females and males, and the ages were estimated from 52 to 166 days for females and 51 to 143 days for males, respectively. The hatching date extended from March to October, with a peak from July to September, suggesting the presence of one spawning group (summer–autumn group). The ANCOVA showed that there was no significant sex difference between the ML and BW growth; however, there was a significant difference between the sexes in the relationship between ML–age and BW–age. The relationship between the ML and BW was best described by the power function, the ML–age relationship of females was best described by linear function; the ML–age relationship of males and BW–age relationships of females and males were best described by the exponential function. B. magister shevtsovi is a high-growing squid, and the growth rate seemed to be high at the young life stage and decreased after the subadult stage (60–120 days older). This study provided basic information on the age, growth, and population structure of B. magister shevtsovi.