Free Swimming Fry in Search of Food

We are pleased to update our proud “fry parents” that your adopted salmon fry are swimming freely in search of food! If your baby fry lives in Kenny Lake school, then your fry has been swimming freely and was fed its first meal of fish food on April 6. However, if your fry lives in the Upstream Learning tank, it is just starting to leave its hiding place under the larger rocks on the bottom, exploring the world above the gravel and figuring out how to maneuver through the water column.

If these eggs were collected and fertilized at the hatchery on the same day, and set up in their home tanks on the same day, why are they developing differently? If you said because of the accumulated thermal units, you are correct!

What is an accumulated thermal unit (or ATU) and what does it mean? The rate of growth for salmon is determined by the water temperature. Up to a certain point, salmon will grow faster in warmer water and slower in colder water. Too hot of water can cause defects or kill salmon, while too cold of water can freeze and kill them as well. By tracking the daily temperature of the water, teachers (and before schools closed, their students) are able to make sure the tank temperatures are safe, but also track the ATUs. For every 24 hours, salmon accumulate the number of thermal units equal to the temperature of their tank. And by adding each day’s temperature to the previous day’s ATU count, we are able to track ATUs and predict when fish will transition to the next life stage.

Now that you know this, can you explain why Kenny Lake’s fish are swimming and feeding already and the fish in Upstream Learning tanks are not quite at the same stage?

If you guessed because of differences in tank temperature, you’re correct!  And if you explained because the Kenny Lake tank is warmer, then you are also correct!

On Friday, April 10, Kenny Lake’s salmon fry had accumulated 641 ATUs while the Upstream Learning tank accumulated 594 ATUs.

Thanks again to all of you who adopted fry to help support this awesome educational opportunity. Also, a special shout-out to our amazing teachers in the region who continue to connect their students to this project by sharing videos on Facebook or incorporating it into their virtual classroom lessons as schools remains closed for the remainder of the school year.

We are excited to work with teachers and program partners to film the release of your fry into the Copper River watershed, so stay tuned!

 Watch the video below for a glimpse into the life of the salmon fry in the Kenny Lake Salmon Tank!

We would like to extend a big thank you to our Salmon Tank Sponsors that contributed funding to the project; Ahtna Intertribal Resource Commission, Prince William Sound Aquaculture Corporation, Valdez Fisheries Development Association, and Copper Valley Telecom. We would also like to thank Mark Proch, Copper River School District/Upstream Learning lead teacher, and Sandy McMahan, retired Glennallen Elementary School teacher for their on-the-ground assistance in getting the tanks set-up.