Neja, Z. (1988) On some problems of reproduction of ruff, Gymnocephalus cernuus (L., 1758) in the Lake Dabie. Acta Icthyologica Piscatoria, pp. 33-50
| Species | Development state | Trait | Primary Data | Secondary Data |
| Gymnocephalus cernua | Egg | Oocyte diameter | The maximum diameter reaching 0.98 (in ova). Other described as 1.03 (range0.90-1.21) | 1.05 mm |
| Gymnocephalus cernua | Female | Age at sexual maturity | All the individuals caught before spawning and belonging to age group 2 and older groups had their gonads at stage 4 or 5, that is they were ready to the nearest spawning. One may infer that some individuals spawn as early as at age 1+. In Poland, it marres at the end of its second year of life. In the river Nadym drainage, it matures at age 2 (usually hower, 3+ or 4+) | 2.0 year |
| Gymnocephalus cernua | Female | Length at sexual maturity | Described as 11-12, but also at 6.5-7.0 [sex not specified] | 11.5 cm |
| Gymnocephalus cernua | Female | Weight at sexual maturity | 20-30 g ! [Different class studied strating at 11.0-20.9 g !] | 25.0 kg |
| Gymnocephalus cernua | Female | Relative fecundity | Mean 1066.3, range 585-1540 eggs/g | 1062.5 thousand eggs/kg |
| Gymnocephalus cernua | Female | Absolute fecundity | 13.338-82.233 | 47.79 thousand eggs |
| Gymnocephalus cernua | Female | Onset of oogenesis | In September, most females (64.1%) had ovaries at stage 2. No stage 4 gonads were found at that time | ['September'] |
| Gymnocephalus cernua | Female | Maximum GSI value | Gonad in stage VI, meaN: 13.81, range 9.52-24.29 [In other study, the coefficient in females migrating to spawn to average 15.6 (9.0-22.0)] | 16.91 percent |
| Gymnocephalus cernua | Male | Onset of spermatogenesis | In September, male gonads were more advanced in development (23.5% and 76.5% at stage 2 and 3, respectively). No stage 4 gonads were found at that time | ['September'] |
| Gymnocephalus cernua | Male | Maximum GSI value | Male in VI stage, were on average 7.11, range 5.26-12.18 | 8.72 percent |
| Gymnocephalus cernua | Spawning conditions | Spawning season | In Polish waters typically from mid-April through end of May | ['April', 'May'] |
| Gymnocephalus cernua | Spawning conditions | Spawning period duration | Started spawning in early May, the spawning lasting no longer than until early June | No data |
| Gymnocephalus cernua | Spawning conditions | Spawning release | Spawing is prolonged and portional, the eggs being laid in two or three portions | No category |