How to Use the ATU Data Sheet
ATU stands for Accumulated Thermal Units. This is the method we use to predict when our salmon eggs will hatch, as well as keep track of the progress of our eggs.
Here's how it works:
- On the day the fish are spawned, measure the water temperature, and record it in the "Today's temp" column, as well as the ATU column.
- Each day, the assigned volunteer goes to the hatchery, records the water temperature in the "Today's temp" columns, and adds it to the previous day's entry in the ATU column.
- For example, if the temperature is 9 degrees on the 7th of November and 9 degrees on the 8th, then the ATU would be 18, then 10 degrees on November 9 = 28 ATU's.
- Once this number hits ~ 250 we will know the eggs are eyed and we can then clean them. The eggs develop according to water temperature, cooler water, slower development.
Below is an example of how we fill in the form
|Nov. 7||9||9||Cloudy||Your Name|
(add this to
plus today's temperature)
|Nov. 9||10||28||Rain||Your Name|
|Nov. 10||8||36||Sun||Your Name|
Here is a chart with some examples of ATU's for various salmon species (Note - we only enhance chum and coho salmon):
|Specie||To eyed stage||To hatch stage||To swim up stage|
|Coho||217 - 237||448 - 475||777 - 829|
|Chum||217 - 250||498 - 546||845 - 1126|
|Chinook||242 - 258||512 - 526||825 - 1029|
|Pink||224 - 257||545 - 662||868 - 1034|
|Sockeye||236 - 257||614 - 694||943 - 1088|
© 2005 Morten Creek Publishing