Common Snowtrout

Common snowtrout is the most common Schizothoracinae in the Himalayas. They can be found in almost all riverine systems of the Himalayas. They are distributed in India, Nepal, Bhutan, Pakistan, and Afghanistan. Water temperature is known to be the determining factor of geographical distribution and dispersal of common snowtrout. This species have the upper tolerance around 20 °C (68 °F) and are able to remain active in the near zero temperature in the streams of Lesser and Greater Himalayas during December and January.

The breeding season for snowtrout has been recorded to occur between June and October with the peak in September. There have been observations indicating that Schizothoracines including S. richardsonii exhibit multiple spawning throughout the year following the temperature rise and flow rates which support egg laying. The female eggs are maturing (not fully mature) around February–May and ready to spawn around August–September, while the male sperms mature in March–April and ready to spawn in July–October. However, the fish spawn during spring despite the relatively immature gonads. The reason is the gonads fully mature in winter, but they are in dormant phase due to the low temperature, thus the fish spawn only on the returning favorable conditions in spring. The rise of temperature in streams from near freezing to 10–17 °C (50–63 °F) during May – June induces common snowtrout to spawn. In Sutlej River, common snowtrout start the migration upstream along with the rise in water temperature in March. During the migration, the fish endure low water temperature of 8.0–9.5 °C (46.4–49.1 °F) due to the steady influx of snow-melt water. This low temperature induces the fish to migrate to side streams where the ground water temperature is around 17.5–21.5 °C (63.5–70.7 °F) to spawn. In other river, Ravi River, this species spawn in May. …