英國塞文河因河運興建多個堰壩，很多會從大海洄游產卵的魚類如鮭魚及鰻魚，已有超過170年未能回來牠們的繁殖地。近年有計劃在四個主要堰壩增加繞道，希望再次開放約240公里的河道，最近其中兩條已完成，團隊期望這個五月能再次看到芬塔西鯡魚的回歸。

Weirs were built on the Severn Rivers in UK for transportations; many fishes like salmons and eels were unable to migrate back for spawning from the ocean for over 170 years. Recent years, there are plans to create routes around four major weirs, and two of them are completed recently; the team is hoping to see the return of the twaite shad, traditionally known as the May fish, this May.

https://www.gloucestershirelive.co.uk/news/gloucester-news/uks-rarest-fish-grace-waters-5397148