This stretch of the Monnow river in Herefordshire looks pristine. Oh. I'm all tangled up. But the anglers here are being taught how to read the warning signs below the water's surface. This is a caddisfly, a cased caddis. I've gone back to school with a group of local anglers who are finding out it's not fish but riverflies that are the key. Head teacher for the day is museum research entomologist Steve Brooks. Now actually, I hope some of you will take it a little bit further than this and get interested in the insects in themselves. Maybe you'll even spend more time looking at the insects than fishing. These larvae are the first things to be hit when the river is polluted. Fewer larvae means fewer fish, and that of course means unhappy fishermen. Well, anglers have got a vested interest in the rivers. They spend a lot of money on their kit, and they spend a lot of money on their licence fees. And so if the fishing isn't any good, they're wanna know why. And they're on the river a lot as well, and they spend half their lives on the river, so they're ideal for having a look at what insects are there and working out what the water quality's like.


曼诺河在赫里福德郡的这一带流域，还保留着原始的状态，都缠在一起了。但是这一水域的垂钓者知道，如何读懂水面下的警示。 这是石蛾，又称毛翅目。 我和一群当地的垂钓者，一起回到学校。他们发现问题的关键不是鱼类，而是河蝇。今天的主讲教师是博物馆昆虫学家史蒂夫·布鲁克斯。我希望你们的工作能够更深入一些，对昆虫世界产生浓厚的兴趣。或许钓鱼之外，你们会花更多时间观察昆虫。当河水受到污染后，这些幼虫首当其冲，幼虫数量减少导致鱼类数量减少，当然渔民也忧心忡忡。在捕鱼业中，渔民有既得利益，他们的装备很昂贵，捕鱼执照费用也不菲。所以如果钓不到鱼，他们想知道原因，他们常常守在河边，几近半生，所以要查明河里昆虫种类，调查河水质量，他们就是理想人选。