• Гідрологія і Гідрометрія
• Господарське право
• Економіка будівництва
• Економіка природокористування
• Економічна теорія
• Земельне право
• Історія України
• Кримінально виконавче право
• Медична радіологія
• Методи аналізу
• Міжнародне приватне право
• Міжнародний маркетинг
• Основи екології
• Предмет Політологія
• Соціальне страхування
• Технічні засоби організації дорожнього руху
• Товарознавство продовольчих товарів

Read and translate the text with the help of a dictionary.

Channel catfish lay eggs in adhesive masses (about 30.000 eggs). Tilapia males construct shallow nests in pond bottoms into which eggs are deposited and fertilized. After fertilization their female picks up the eggs in her mouth and retains them until after the fry hatch and are able to survive on their own. Trout and salmon lay their eggs in shallow nests (known as redds) constructed in the gravel bottoms of lakes and streams. The newly hatched fish remain in the gravel for a considerable amount of time after hatching.

In order to control reproduction in the hatchery environment, the aquaculturist must understand how to species of interest behaves under natural conditions. These conditions can be replicated then. In some instances, however, culture environments have been set up to duplicate natural conditions, but the brood animals refuse to spawn. Under those circumstances hormone injections can be used to induce spawning. Once fertilized eggs are obtained they need to be incubated under the proper conditions (temperature and light may be important, as are dissolved oxygen level and, in case of marine fishes, salinity among others).

Eggs of trout, salmon and catfish are relatively large and resilient, so high water flow rates are tolerated. The eggs of many species, however, tend to be susceptible to mechanical damage, so care must be taken to provide a calm environment to prevent the eggs from bumping into each other or into the walls of culture tanks. Various marine fishes fall into the latter category, as do many invertebrates. At the same time, some exchange of water is required to dilute waste products like ammonia which are produced by developing eggs and larvae.

Some eggs hatch into larvae within 24-48 hours after fertilization, while others may require several weeks or even months of incubation. Generally, warm water species develop and hatch quickly, while cold water species require considerable time period for development.

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