It is always an exciting time when the eggs arrive and the anticipation begins for the date that the eggs ultimately hatch. Did you know that the actual date can be calculated? Simply follow the math outlined here:
The specific time it takes for eggs to hatch is measured in Accumulated Thermal Units (ATUs). It takes about 450 ATUs to hatch brook trout eggs. ATUs are measured in the # of days multiplied by the water temperatures in Celcius. To calculate your hatch date, you will need to know the date that the eggs were fertilized and the water temps that they have been kept at. For those classes that received eggs on October the 12th, your eggs were fertilized on September 13th and have been in constant 52 degree (Farenheit) water until delivery from your classroom.
If, for example, your eggs were 20 days old and were kept in 54 degree (F) water, which is 12.2 degrees Celcius, you would do the following calculation: 20 days multiplied by 12.2 degrees (C) = 244 ATUs. Then subtract 244 ATUs from 450 (number for brook trout to hatch) and you wind up with 206 ATUs left until hatching. To determine days, simply divide 206 (# of ATUs left) by 12.2 degrees (water temp in Celcius) to find 17 days (rounded up) until the eggs will hatch. If you lowered your tank’s temperature to 52 degrees (F) after 20 days, you would wind up with 11 degree (C) water and 21 days remaining until the eggs hatch. Raising the temps would result in less time until hatching.
To easily convert Farenheit to Celcius, click on this easy to use N.O.A.A. site: www.wbuf.noaa.gov/tempfc.htm