SUMMARY. 1. The literature contains a number of curves relating time (days) required for median hatch (=D2) to water temperature (T,°C) for the eggs of several salmonid fishes. There are relatively few data on the relationships between time to median eyed (= D1), days) or time to median swim-up (= D3, days) and temperature.
2. From published data, over most of the range 0-9.5°C, approximate relationships are D,=0.5D2 for Atlantic salmon (Salmo salar L.) and D3 = 1.7D2 for eight species of Salmo and Oncorhynchus.
3. Field and hatchery tests suggest that these are useful empirical models for approximate prediction of D1 and D3 from D2 for most salmonids.