Forget Nessie: there's another insidious creature living in the waters of Scotland. The story starts in the streams and lakes of the northwestern United States, where North American signal crayfish are a familiar sight. Turn over a rock and you may well encounter one. But in Scottish streams and lochs, these creatures are intruders. American crayfish may be destroying the catch.
别去想什么尼斯湖水怪了，苏格兰的水域中潜伏着另一种有害生物。它们起源于美国西北部的溪流和湖泊，美国北部的人民对小龙虾已经见怪不怪了。翻开一块石头就能发现一只。然而在苏格兰，这种生物却是入侵者，美国小龙虾可能会毁掉苏格兰的生态。
Allen Pleus, with the Department of Fish and Wildlife in Washington State, says that the signal crayfish is an important species in his region. It's the only native crayfish species, and the freshwater crustaceans are just another part of the ecosystem. "They play well with others," he says. "They've learned to be good neighbors with the other native species." But those same crayfish wreak havoc in Scottish waters.
华盛顿鱼类和野生动物的艾伦·普鲁伊斯说小龙虾在本地是很重要的物种。这是唯一的本地小龙虾种，而淡水甲壳动物是生态系统的另一部分。“它们彼此相处得很好，和其他本地物种也相处融洽。”但是同种的小龙虾却在苏格兰肆虐。
Matt Mitchell has been casting his line into these waters for about 40 years. "This area is probably, if not the best, certainly one of the best trout fisheries in the world," he says. One day Mitchell got a call from an angler friend. The conversation changed Mitchell's life. "I could not believe the number of crayfish that were in this part of the river. You could literally walk across the river standing on crayfish!"
麦特·米歇尔在这片水域作业有40年了。“我们这有世界上数一数二的鳟鱼，”他说。然而有一天他接到了来自钓友的电话，而这个通话改变了他的一切。“我简直无法相信这里有多少小龙虾。你甚至都能踩着它们过河！
The North American signal crayfish, which had been introduced to English waters decades ago and spread steadily north, were taking over. "They were big animals. I mean, some of these things were about 10, 12 inches long." At that size, they don't even look like crayfish; they look like lobsters. Animals that big, Mitchell says, are more than a decade old; he guesses they've been in the river for 12 years.
北美标志性的小龙虾是在数十年前被引入英国境内，并且向北蔓延最后占据了水域。“它们实在是很大，有一些都能长到10、12英寸。”有着这样的尺寸，它们甚至看起来不像小龙虾更像大龙虾。米歇尔说，这么大的动物起码有十岁以上，他认为这些至少是十二年的小龙虾。
The problem isn't just the size or quantity of the intruders; it's that the signal crayfish eat the same insects and larvae as the prize-winning trout that are native to these streams. Mitchell's colleague Ian Miller is the man who first placed that concerned phone call from the Clyde Burn all those years ago. With the arrival of the crayfish, Miller says, "Stoneflies are gone — basically wiped off the face of the Earth." That's a problem, because stoneflies are an important food for the fish. No trout food means no trout.
问题不是只在于这些入侵者的尺寸或者数量，而是这些小龙虾会吃掉同样生活在这片水域的鳟鱼赖以为生的浮游生物。米歇尔的同事伊恩·米勒是很多年前就第一个认识到这个问题的人。米勒说，小龙虾的到来使得“石蝇消失了，基本上就是灭绝了。”这是问题所在，因为石蝇是鱼类重要的食物来源。没有食物，就没有鳟鱼。
Turns out, Washington State is struggling with a similar problem. "Unfortunately, we now have our own invasive-species crayfish in this area — mostly red swamp crayfish from the southern United States," he says. That's right. At the same time that the North American signal crayfish are taking over rivers and streams in Scotland, they're being crowded out of rivers and streams in their native habitat byother invasive crayfish — interlopers from Louisiana.
实际上，华盛顿也面临着同样的问题。“很不幸，我们这也来了一群不速之客，大多数是来自美国南部的红沼泽螯虾。事实也如此，当苏格兰的江河溪流被美国北部的小龙虾侵略时，来自路易斯安那州的小龙虾也占领了华盛顿的地盘。