BRIDGTON – Students from four area elementary schools have been raising salmon since February, and now the fish have reached the “fry” stage.

That doesn’t mean they’re ready for the pan.

The fifth- and sixth-graders from Stevens Brook Elementary in Bridgton, Harrison Elementary and Crooked River in Naples, and Waterford Memorial School will take a field trip to release the fish into Crooked River, said Bridie McGreavy, a community educator for Lakes Environmental Association in Bridgton.

McGreavy said the school salmon project is part of a larger Adopt-A-Salmon project coordinated through the Portland Water District. The Lakes Environmental Association works with them to involve the schools, and the District helps arrange the permits necessary to raise, transport and release the salmon.

Interested schools will write a grant for about $800 for the chilling unit and tank, she said. This type of learning project fits well with fifth- and sixth-grade curricula, and students are old enough to be conscientious about the care of their fish.

The first part of the project is a trip to Casco hatchery where children get to see the eggs that will be in their tanks and to learn about the growth cycle of their salmon.

McGreavy explained the differences between these fish and Atlantic salmon: These are landlocked salmon and are not endangered. They will spend all their lives in fresh water. Atlantic salmon, on the other hand, are born in fresh water, migrate to the ocean and then return to fresh water to spawn.

Classes got their salmon at the egg stage Feb. 1, with 300 eggs to a tank. By the third week, eggs hatched to the “alevin” stage in which they have a yolk sac that provides nutrients, she said.

Alevin spend their time lying on the sandy bottom digesting the yolk, and once that nutrient source is used up, they need to find food. That’s the “fry” stage, when they can be released. It takes three years from egg to adult, she said, from egg to eyed egg to alevin to fry to parr to smolt to adult salmon.

The tanks with chilling units keep the eggs cold, just as they would be in a cold, mountain stream. Water temperature controls development, she said. “If we keep the tank cold longer, they stay alevin longer. If we heat it up, they develop more quickly.”

The chilling units run on electricity, and Jim Thornton’s fifth-grade class in Waterford lost half their tank during a power outage. McGreavy said the backup tank she’s been nurturing at LEA will be released into Crooked River along with what fish remain in Waterford’s tank during their field trip Tuesday, May 27.

In one of their lessons, she said, students are divided into groups and each group gets an alevin, which are transparent at this stage, to observe. They can only be out of the water for five minutes, but students can observe the heart beating while they also learn important lessons about caring for the fish.

The salmon release is an exciting field trip, McGreavy said, and they also do aquatic insect sampling. Before issuing permits to release salmon into Crooked River, Inland Fisheries and Wildlife already has determined that the water will be suitable habitat with the right kind of bugs. Kids will see caddis flies, mayflies and stoneflies, and it’s good for kids to see that their salmon will be well fed in clean water, “a good lesson in food chain and healthy eco-systems,” McGreavy said.