为什么会有鱼儿游来游去？我们先来看看三文鱼吧。三文鱼是一种生活在北半球淡水和海水交界处的鱼类，又被称为大马哈鱼或鳟鱼。它们有着美丽的银白色身体，背部呈深绿色，在河流和海洋中留下优雅的身影。

Why do fish swim? Let's take a closer look at the salmon. Salmon is a type of fish that lives in the fresh and saltwater areas of the northern hemisphere. It is also known as the Chinook or trout. They have beautiful silver bodies with a dark green back, leaving an elegant presence in rivers and oceans.

三文鱼之所以会游，与其独特的生命周期密切相关。三文鱼有着惊人的迁徙能力，每年都会进行长途旅行。它们从淡水中孵化出来后，开始游回大海。在海洋中度过几年时间后，它们会靠着本能回归到自己孵化地的家乡河流。这段迁徙距离可能非常长，甚至上千公里。三文鱼的内部罗盘能够帮助它们找到正确的方向，确保能准确无误地回到故土。

The reason why salmon swim is closely related to their unique life cycle. Salmon have an incredible migratory ability and undertake long journeys every year. After hatching in freshwater, they start their journey back to the ocean. After spending a few years in the ocean, they instinctively return to their native rivers where they were hatched. This migration distance can be very long, even thousands of kilometers. The internal compass of the salmon helps them find the right direction, ensuring they return home accurately.

除了生命周期的影响，三文鱼的游泳能力也起到重要的作用。它们的身体形态和游泳肌肉结构使得它们非常擅长在水中自如穿梭。三文鱼拥有流线型的身体，背鳍和尾鳍的结构帮助它们在水中迅速推进。游泳肌肉的发达让它们具备了强大的爆发力和持久力，使得长途迁徙成为可能。

In addition to the influence of their life cycle, the swimming ability of salmon also plays an important role. Their body shape and muscular structure make them highly adapted for seamless navigation in water. Salmon have streamlined bodies, and the structure of their dorsal and tail fins helps them propel through the water quickly. Well-developed swimming muscles give them strong bursts of speed and endurance, making long-distance migration possible.

最后，三文鱼的游泳行为也与其寻找食物有关。它们在海洋中以浮游动物、小鱼和甲壳类为食，在游动的同时捕食。游泳对于三文鱼来说是一种有效的方式，帮助它们在水中搜索并追逐食物。

Lastly, the swimming behavior of salmon is also related to their search for food. They feed on plankton, small fish, and crustaceans in the ocean while actively swimming. Swimming is an efficient way for salmon to search and chase down their food sources in the water.

总之，三文鱼之所以会游，是因为它们特殊的生命周期、游泳能力和寻找食物的需求。这些因素共同作用，让三文鱼得以游进我们的视野，并留下了丰富多彩的足迹。

In conclusion, the reasons why salmon swim are due to their unique life cycle, swimming ability, and the need to find food. These factors work together, allowing salmon to swim into our view and leave behind a rich and colorful trace.