Like its relative the powan (C. lavaretus), this fish was isolated in inland waters during the last ice age; since then local populations have developed a number of individual characteristics. The vendace, some 8-l0in (20-25 cm) in length, has a protruding lower jaw and shares with the powan and other salmon species an adipose fin situated between dorsal and tail fins. The body is silvery in colour and its shape resembles that of the herring, which has given rise to another common name for these fish - freshwater herring. The vendace feeds on plankton in the upper levels of the loch, a characteristic it has in common with herring.