한국 서해 상괭이 (Neophocaena asiaeorientalis)의 성장과 성성숙

Abstract

A total of 111 finless porpoises (Neophocaena asiaeorientalis) were collected in the coastal water in the Yellow Sea, Korea from March to June in 2010. Age, growth and sexual maturity were described from 51 female and 60 male specimens caught incidentally in stow nets. Ages were determined by counting growth layer groups (GLGs) in the dentine from thin cross sections of teeth. Testis and ovarian samples were examined macroscopically and microscopically. Females were in the 1 to 16 age range and the 92.6 to 149.7 cm long body length range. Ages and body lengths of male ranged from 1 to 19 and from 87.9 to 229 cm, respectively. The biggest male is 229 cm long and bigger than any other finless porpoises in the previous studies. Body lengths of the smallest sexually mature male and female were 125.3 and 131.6 cm, respectively. Using the sum of immature fraction algorithm, males were estimated to attain sexual maturity at 4.75 years and 133.8 cm while females reached sexual maturation at 5.4 years and 134.52 cm. Mature testis weights ranged between 5.6 and 898 g. Testis mass and the diameter of seminiferous tubule showed obvious increases as males became mature sexually. Relatively large number of females were pregnant. In order to clarify breeding season, collection of samples all the year round would be necessary.