Prediction, from temperature, of eyeing, hatching and ‘swim‐up’ times for salmonid embryos

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