Choose the right word for each gap.

During the 20th century large swathes of the Volga River were poisoned and its natural 1) ... was destroyed. The impact on its wildlife was devastating. Breeding areas were affected, and the poisonous water 2) ... that the number of fish plummeted. Imposing dams, overfishing and the poaching of fish for caviar were some of the other problems affecting Russia’s main river.
Fortunately, the Russian government started taking steps towards restoring the river. Programmes were established to make the water cleaner and safer and to minimize the industrial pollution affecting the river. Fish farms were also 3) ... in order to help repopulate the water. The world’s largest freshwater fish, the Beluga sturgeon, which has 4) ... the river for hundreds of years is now 5) ... from a rise in numbers.
Today, work is continuing and the Volga River is well on its way to full recovery. The fish are plentiful and able to 6) ... naturally in the cleaner water. Further action is being taken to limit the pollution deposited in the river by factories, and fines are being 7) ... on illegal fishing. Due to efforts by the Russian government, the future looks brighter for the Volga River as it is restored to its former glory.