The Morten Creek Salmonid Enhancement Project is a community initiative dedicated to restoring and protecting the salmonid populations of the Lynn Creek Watershed in North Vancouver, BC.

Morten Creek SEP
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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:
  1. 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.
  2. 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.
  3. 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.
  4. 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
Date Today's temp ATU's Weather Name
Nov. 7 9 9 Cloudy Your Name
Nov. 8 9
(add this to
yesterday's ATU)
18
(Yesterday's ATU
plus today's temperature)
Cloudy Your Name
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