Stage I: Immature

Strand-like Y-shaped gonad and transparent. This stage is dominated by spermatogonia only

Stage II: Developing

Easily distinguishable as males and off-white colored gonads. The majority of the cells are spermatogonia, and spermatocytes but occasionally few groups of spermatids and very few spermatozoa are observed

Stage III: Spawning capable

Large gonads, off-white coloration; dominated by lobules filled with spermatozoa

Stage IV: Regressed

Reduced in size with bloody perches. Other portions still look off-white. Microscopically they are large empty spaces with residual spermatozoa. However other portions may still have some viable spermatozoa.

Stage V: Regenerating

Further reduced in size with pale reddish coloration. This stage largely contains parked spermatogonia with reduced spaces containing very few residual spermatozoa.