Fast growth and maturation of gametes in most sea urchins takes place in winter, not long before spawning. By breeding season only one generation of mature gametes is differentiated in ovaries of each female. In males active gametogenic processes begin earlier than in females. In summer, newly formed spermatozoa are already contained in tubuli of most specimens. Spermatogenesis continues in autumn and winter.
Gonadal index is maximum at the spawning stage and minimum at postspawning.
In summer and autumn gonad weight gradually increases and attains rather high values in September-October, especially in 1995. Different organic components probably accumulate in gonads for further rapid oocyte growth. Apparently, the water temperature and phytoplankton do not stimulate the beginning of sea urchin spawning. However, together with an increase in light regime they create conditions favorable to the green sea urchin breeding in the coastal areas.