Sushi is considered as the traditional Japanese food, which is very famous around the globe. Sushi became one of the expensive foods in Japan but used to be a fast food, sold outside, citizens of Edo(former name of Tokyo) enjoying at the street vendors.
One of the type of sushi is called Edo-mae zushi(sushi). Edo is the former name of Tokyo which was used during the Tokugawa shogunate era, before the residence of emperor of Japan moved from Kyoto to Tokyo. Then, MAE means in front of. Therefore Edo-mae should mean in front of Edo. What is in front of Edo? The answer is Tokyo(Edo) bay.
Edo-mae sushi should use the fishes and seafood caught in Tokyo bay. Therefore the sushi should be fresh. Especially conger eel; anago in Japanese, is told that the conger eel caught in Tokyo bay is the best.
Tokyo bay was polluted heavily between 60s and 70s, when Japan enjoyed the Japanese economic miracle, rapid economic growth. However, Japanese was not keen on environment during this miracle and let the drainage from the factories sewage. However, the quality of the water is improving and the bay is becoming better than before. Anyway, the fishes caught in the bay should be tough after surviving in such harsh environment. It is similar to human being. A kid who was grown up in a big slam should be more stronger against diseases that the city born kid.