Vocabulary

wild brood stocks	косяк (стая) рыб в реке
captivity	неволя
brood fish	ручьевая рыба
spawn	нереститься, выметывать икру
fall	осень
to broadcast	разбрасывать
to fertilize	оплодотворять
to hatch	выклевываться
benthos	бентос – донные живые организмы (личинки насекомых и др.)
nekton	нектон
red drum	красный горбыль
striped bass	полосатый окунь

11.4 Translate the given Russian words into the English ones:

1) Some species spawn in fall or (зима), some in (весна).

2) The key to inducing spawning may be changing temperature such as falling temperature late in the year or (повышение) temperature in the spring.

3) Increasing or (уменьшение) the amount of daylight present.

4) The larval animals may swim about in the plankton to enter the benthos or (нектон) community.

11.5 Topic for discussion

1. Speak about conditions required for reproduction.

Part 2

0. 11.6 Read the following international words and translate them. (Mind the part of speech).

1. Natural, hormone, injections, product, ammonia, incubation, periods, mechanical, category.

3. 11.7 Give Russian equivalents of the following words and word combinations.

0. Adhesive masses, hormone injections, shallow nests, warm water species, proper conditions, brood animals, to induce spawning, mechanical damage, waste products.

11.8 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.