The story starts in the streams and lakes of the northwestern United States, where North American signal crayfish are a familiar sight.
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。
2
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."
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。
3
The North American signal crayfish (Pacifastacus leniusculus) is one of several species introduced into the UK for aquaculture in the 1970s, and which have since made themselves right at home.