A single yellow daffodil clings to a grassy bank above the foam-flecked waters of the White Cart. A line of children carrying clear plastic bags marches purposefully past. Rain has been falling for days, the river is in spate and adults in the party are looking a little anxious.

“We’ve had thousands of schoolkids releasing young trout into rivers over the past few years,” says Dr Willie Yeomans, the Clyde River Foundation’s catchment manager, “but we’ve never had weather this bad.”

As the children tramp across a muddy pasture in Pollok Park, Glasgow, some seem concerned about the prospects of the trout fry they are carrying. The fish are so small and the river so fast-flowing: won’t they simply be swept away?

The carefully chosen location for their release, in shallow water around a sand and gravel bar, will provide some safety, Caroline McGillivray, the foundation’s education officer, explains.

“The first thing they do is burrow down into the stones. Then slowly they make their way out to mid-channel.

“Down at the river bed is a layer of water that barely moves, so the fish stay in that until they grow bigger, eating the wee bugs and things that live there.”

Downstream, the White Cart joins the Black Cart and then flows into the Clyde at Renfrew.

As the children take turns to tip out the contents of their bags, the darting, dark-eyed slivers of life they have tended for weeks vanish into the wild.

“You can’t see them because they’re camouflaged,” explains Lewis, 10, of Broomhill Primary.

“They used to be eggs. Then they were alevin. Now they’re fry, which is the first stage that they look like fish. After that they turn into parr. Then they become smolt and then adult sea trout if they go to sea, or adult brown trout if they don’t. It’s really interesting.”

No one ever sees in the wild what these children have seen, Dr Yeomans says. “Trout lay their eggs in nests on the river bed and when they hatch they stay there for weeks until they absorb their yolk sac. Then they burrow up through the stones.

“They are territorial and don’t like to be close to each other.”

“They have all hatched from the eggs of one trout. So they are brothers and sisters,” explains a group of Broomhill Primary girls, who have given names such as Chelsea and Chloe to their trout. (“They look like girl fish because they’re cute,” they say.) “At school they showed us a video of them squeezing a girl trout gently so her eggs came out. Then they got the juice from a boy trout to fertilise them.”

As the Broomhill Primary pupils head home, their place is taken by a new group with similar bags of fish in their hands and excitement in their eyes.

“Gone are the days when you could pick up frog spawn at a local pond and watch them mature,” says Ray Evans, the P7 teacher at Ralston Primary in Paisley. “So this is a great way for kids to learn about the complexities of life.”

This is the second year his school has taken part in the Clyde in the Classroom initiative, which the foundation, a small charity with three employees, runs in partnership with Glasgow Science Centre. It is part-funded by Scottish Natural Heritage and nine participating local education authorities.

The children get really involved, Mr Evans says, studying the fish and keeping them cool with ice packs. The Clyde River Foundation staff come and talk to them and provide a pack about the life cycles of fish and the environment, 250 trout eggs and a hatchery for the pupils to take care of the fish until they are released. “In the classroom we go into the science and the whys and wherefores.”

Having cared for the trout since they were eggs, the children have mixed feelings about their release.

“They know there are a lot of predators out there,” says Mr Evans, “but they also know the river is where they belong and it’s time for them to go.

“This project is a great way to bring the natural world into the classroom.”

Dr Yeomans, a practising scientist who spends much of the year surveying fish populations and habitats in the Clyde catchment area, says he has been astonished by schoolchildren’s response to Clyde in the Classroom.

“Teachers must see it all the time, but I think it’s fantastic the way kids take all this and make it their own,” he says.

“This is a big project and growing all the time. We have 44 schools taking part this year.

“This is easily the best and most rewarding thing I’ve ever done.”

For Clyde in the Classroom details Ccntact Caroline McGillivray c.mcgillivray@bio.gla.ac.uk or Dr Willie Yeomans w.yeomans@bio.gla.ac.uk