根据以下资料，回答下列各题。
[1] Fishing is probably the world’s most popular sport. People spend many dollars each year on items like boats and four-wheel-drive vehicles. In addition, they spend money on fishing equipment , bait, fuel and boat repairs. And you can see that fishing can be an expensive pastime. Fishing lovers believe that their hobby is worth it. Others say that fishing is spoiling the environment and that it is a cruel hobby.
[2] Supporters of fishing say that it is a nice hobby. Firstly, of the millions of people who fish for fun, most only catch enough fish to feed their families. They catch fish that are found in large numbers, so there is little danger to the species (种类).
[3] Secondly, recreational fishermen contribute to the economy. They spend money on equipment and other items, and they also spend it indirectly by paying taxes on their equipment and fuel. Those who travel to fishing spots pay for accommodation (食宿) and airfares. This money keeps people in work and provides new jobs each year.
[4] Thirdly, fishing is relaxing and fun so it lessens stress. Instead of turning to drugs or alcohol, it is far better to go fishing. People who are relaxed are generally healthier and much nicer to be near ----- except for the smell of the bait !
[5] Those who _________________ say that there are too many fish thoughtlessly taken form. rivers, lakes, streams and oceans. This could lead to the dying out of some species. Modern cars and boats mean that people can fish in remote areas of the world, so no place is safe from greedy fishermen who take both males and females, leaving few fish to produce young.
[6] Those against fishing also say that it is a blood sport, which means that an animal must die so that a human can have fun. Many of the fish caught for sport are not suitable for eating, so they are thrown away. Once hooked, fish have no chance of escape.
What is the main idea of the passage ? (no more than 4 words)
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