Leino and McCormick, J.H. (1997) Reproductive characteristics of the ruffe, Gymnocephalus cernuus, in the St. Louis River estuary on western Lake superior: a histological examination of the ovaries over one cycle. Can. J. Fish. Aquat. Sci., pp. 256-263
| Species | Development state | Trait | Primary Data | Secondary Data |
| Gymnocephalus cernua | Female | Oocyte development | Group- synchronous, multiple clutches [ovaries may contain several oocytes stages simultaneously] | Synchronous |
| Gymnocephalus cernua | Female | Onset of oogenesis | September slight increase | ['September'] |
| Gymnocephalus cernua | Female | Intensifying oogenesis activity | March-April | ['March', 'April'] |
| Gymnocephalus cernua | Female | Maximum GSI value | 8-11 [April] | 9.5 percent |
| Gymnocephalus cernua | Female | Resting period | 2-3 [June, July and August] | 2.5 months |
| Gymnocephalus cernua | Female | Resting period | <1 | 1.0 months |
| Gymnocephalus cernua | Spawning conditions | Spawning season | Late April to Mid-June | ['April', 'May', 'June'] |
| Gymnocephalus cernua | Spawning conditions | Spawning period duration | 8 | 8.0 weeks |
| Gymnocephalus cernua | Spawning conditions | Spawning depth | Most spawning occurs at a depth of less than 1 m | 1.0 m |
| Gymnocephalus cernua | Spawning conditions | Spawning release | More than one clutches of eggs per spawning season, intermittent spawner | Fractional |