Sexual Maturity of Isaza (Chaenogobius isaza)-I
The Seasonal Changes of Growth and Sexual Maturation
1974 Volume 40 Issue 9 Pages 847-857
Details
1974 Volume 40 Issue 9 Pages 847-857
The processes of sexual maturity of isaza (Chaenogobius isaza ?? T) were studied by comparing various quantitative indices such as seasonal changes of body length, body weight, muscle weight, hepato-somatic index and gonado-somatic index.
Females could be distinguished into mature and immature ones in and after December by direct observation of the gonad with a naked eye. Mature 0+ females were larger than immature 0+ females and the critical bdoy size seemed to be about 40mm in standard body length in December. Immature 0+ females seemed not to mature to spawn supplementarily after December.
The mean liver weight and mean hepato-somatic index of 0+ fish increased rapidly from September to January, and began to reduce from February. The mean hepatosomatic index of females was greater than that of males before February, but became reverse thereafter. The mean hepato-somatic index of immature 0+ females was smaller than that of mature ones in September and kept increasing gradually. Results of chemical analysis indicate that liver is a main reservoir of lipids as a source of materials and energy for maturation and spawning.
All these results suggest that the stage of maturation of isaza coincides with a definite body size accompanied with the completion of enlarging the liver.
