Hoffmann, R.P. and Wondrak, P. and Groth, W. (1980) Seasonal anatomical variations in the testes of European pike, Esox lucius L. J. Fish. Biol., pp. 475-482
| Species | Development state | Trait | Primary Data | Secondary Data |
| Esox lucius | Male | Onset of spermatogenesis | Stage 2, from Septemeber to November | ['November'] |
| Esox lucius | Male | Main spermatogenesis activity | Stage III, stage of maturity : December to March/April | ['January', 'February', 'March', 'April', 'December'] |
| Esox lucius | Male | Maximum GSI value | 2.04 ± 0.78 [From December to April] | 2.04 percent |
| Esox lucius | Male | Resting period | Stage I, rest from June to August, and stage IV, stage of post-spawning March to May | 7.0 months |