Witkowski, A. and Blachuta, J. and Kokurewicz, B. and Kowalewski, M. (1989) Changes of gonado-somatic index (GSI) and egg diameter in the grayling Thymallus thymallus (L.) in annual cycle. Acta Ichthyologica et Piscatoria [ACTA ICHTHYOL. PISC.], pp. 21-28
| Species | Development state | Trait | Primary Data | Secondary Data |
| Abramis brama | Female | Resting period | About one month | No data |
| Rutilus rutilus | Female | Resting period | 1.5-2 months, but could be shorted in heated reservoirs | 1.75 months |
| Coregonus albula | Female | Resting period | About 2 months | 2.0 months |
| Thymallus thymallus | Egg | Oocyte diameter | Mean 2.67, up to 2.9 [Egg immediately before spawning] | 2.67 mm |
| Thymallus thymallus | Female | Onset of oogenesis | July and then increase regularly | ['July'] |
| Thymallus thymallus | Female | Intensifying oogenesis activity | The most intense growth takes place as late as autumn and winter (September-March) | ['January', 'February', 'March', 'September', 'October', 'November', 'December'] |
| Thymallus thymallus | Female | Maximum GSI value | Mean of 15.7 but up to 18% [The highest GSI values are observed in March and at the beginning of April] | 15.7 percent |
| Thymallus thymallus | Female | Resting period | About two months: May and June | 3.0 months |
| Thymallus thymallus | Female | Resting period | 0.8 [May and June] | 3.0 months |
| Thymallus thymallus | Male | Onset of spermatogenesis | Mid-July, slight increase | ['July'] |
| Thymallus thymallus | Male | Main spermatogenesis activity | August then remained almost constant during the winter | ['January', 'February', 'March', 'August'] |
| Thymallus thymallus | Male | Maximum GSI value | Mean 1.63, up to 2 [September] | 1.63 percent |
| Thymallus thymallus | Male | Resting period | 0.3% [Three months after spawning May -July] | 3.0 months |