Young Perch (1981)

[music] >> The lake of perch. The young perch. Down in the lake, the perch are ready to breed. That's what we call it when they're going to have young. Let's see how they do it. >> [music] >> There's a perch. >> [music] [music] [music] >> There's another. >> [music] [music] [music] >> A male and a female. They can have young together. >> [music] [music] >> Playing like this is called courting. >> [music] [music] [music] [music] [music] >> Now they must find a good place to breed. >> [music] [music] >> Is this place good enough? >> [music] >> Hello. Here's another one. >> [music] [music] >> The female wants both of them to follow her. >> [music] [music] >> Now she's going to lay her eggs. The eggs are joined together in a long chain. The two males shed sperm on them. The egg chains with sperm on them are hung in old branches which have fallen into the lake. >> [music] >> Now that they've finished, the female drives the two males away. They're likely to eat the eggs. >> [music] >> She stays behind to guard the eggs. >> [music] >> Although she watches carefully, she doesn't see everything. >> [music] >> Some of the eggs are eaten by a larva. >> [music] >> Inside the eggs, the young begin to develop. If the water is warm, they grow rapidly. >> [music] [music] >> When they hatch out, the female swims away. The newly hatched fish are called fry. They have a lunch pack on their bellies, which we call a yolk sac. This keeps them going for a few days. The fry drift with the current into shallow water. It's warmer here. When the yolk sac is used up, they eat plankton. Some of the fry are eaten themselves, by sticklebacks, for example, or they die if they can't find enough food. It's dangerous [music] to be a newly hatched fish. If we observe 20 newly hatched perch, or perch fry, we find that after just one day, only 10 are alive. After 2 days, there are only five. After 3 days, there are only three. After 4 days, there might be only one. But there are many lots of 20 perch fry, fortunately. >> [music] >> If the water is warm enough, and there is enough to eat, they grow rapidly. >> [music] >> Now they begin to develop stripes and red fins, like the fully grown perch. A young fish has to eat a lot of food every day in order to grow well. Either a good many water fleas, they're a kind of very small crayfish, or two small fish. >> [music] [music] >> When they are full, they rest. >> [music] [music] [music] >> At night, the perch sleep, even though they can't close their eyes. That's because they have no eyelids. But not all the animals sleep. >> [music] >> Here's a small crayfish. It looks for food at night. There's a larva. >> [music] >> There's a frog. The eels awake at night. It sniffs its way forward. >> [music] >> Early in the morning, the carp swims around, >> [music] >> even though it's so big. It's not a danger to the perch. >> [music] [music] >> Now they're hungry. They're going out hunting. >> [music] >> There are some bleaks. >> [music] >> There are tadpoles, too, here in the shallow water. >> [music] [music] [music] >> What's that? Oh, it's just a man. And there's nothing but tadpoles in his net. The young perch dart away. They flee into the middle of the long water plants we call straight weed. Now they're in deep water. >> [music] [music] [music] >> But there are dangers here, too. >> [music] >> The lake's biggest fish of [music] prey is the pike. Where have the perch [music] gone to? >> [music] [music] >> There they are. >> [music] [music] [music] >> Now, they've grown so big that they begin to play in just the same way as the fully grown perch do when they're about to breed. >> [music] >> They're eating water fleas here. [music] >> [music] >> The bleaks are hard as a catch. >> [music] [music] [music] >> The pike's hungry, too. >> [music] [music] >> The hunt for bleaks [music] continues. >> [music] >> The perch that survive are fully grown in 2 or 3 years. >> [music] [music] [music] [music] [music] [music] [music]