These are what you would see emerge from a salmons gravel nest best known as redd. Fry push themselves vertically up to the surface of the water, usually taking several hours right after nightfall, when they will be less visible to predators. They snap their mouths into the air, hold their gills closed and force a mouthful of air into a swim bladder, an organ that is like a balloon in their abdomen. They might have to repeat this motion a few times until they have enough air to hold their position in the water. Fry are not strong enough to swim upstream, so they drift downstream until they find calm pools where they can feed. There, they defend a small feeding territory from other fry. They catch land insects that fly close to the water or fall from plants hanging over the water. They also catch food in the water, mainly insect nymphs and larvae, as well as plankton. They grow from about 2.5 cm to between 4.5 and 5.5 cm. Because they are out in open water searching for food, many salmon fry are eaten by predators, including birds and larger fish. To hide, salmon fry change their skin colour. They develop camouflage markings known as Parr marks, which are dark bars across their bodies. The mixture of light and dark helps them blend into the shadows on the stream- or lakebed so they are less visible to predators. They also dart very quickly from spot to spot. A crucial part of the salmon’s life cycle occurs at the fry stage — imprinting. Salmon fry memorize their home stream or lake through factors such as the type of rock and soil in the bed, plant life and other aquatic organisms, all of which contribute to the quality and the unique scent of the water. Salmon learn to recognize this scent as very young fry and can identify it in the water when they return from the ocean. Changes in the stream’s environment that occur after the fry leave can confuse the returning salmon, preventing them from finding their home stream and spawning. Imprinting continues as the fry grow and become smolts, so fry raised in an aquarium use these memories, rather than memories of tap water used in aquariums, to find their way home. Almost 90 per cent of all fry die from predators, disease or lack of food. People can help increase fry survival by protecting their environment from pollution, flooding or blockages. Fry need fresh, f lowing, cold water, with plenty of oxygen and shade to keep the water from getting too warm. They also need places to hide, such as large boulders, overhanging bushes, tree stumps or fallen logs. Depending on the species, salmon spend from a few days to three years in their home stream or lake. Then, they begin to migrate downstream to the estuary where the river meets the ocean.