Gonad Staging

Photo Caption: Female in early developing oocyte with cortical alveoli. It is indicative of the transition from immature to mature in the
reproductive cycle.

By Catalina Brown

The FWH group’s research project, Monitoring Offshore Reef Fish Populations, includes a comprehensive gonad staging section. Gonad staging is incorporated along with a series of other organosomatic indices which will then be applied to increase knowledge of the overall health status of specific fish species. Organosomatic indices in fish can be modified by environmental stressors, nutrition, reproduction and age. Our objective is to assess reproductive maturation, distinguish groups between males, females and transitional hermaphrodites and eventually compare health indices between fish in the same phase of reproductive maturation to identify implications of life history.

We assigned two distinct phases for males: developing/regenerating and spawning capable. Females are multifaceted, and undergo several phases of maturation. Therefore, females are categorized as immature or mature, and mature females can be further divided into three distinct sub-phases: developing, spawning capable or regressing. These phases are based on morphological changes that occur through development. Health indices of fish that are of the same sex and reproductive phase will be compared to determine if individuals at each stage are allotting a comparable proportion of energy towards reproduction.

The relationship between Organosomatic indices and gonad developmental phases will eventually provide a clear correlation between life history and overall fish health.