It is mainly yellow-brown in colour, although occasionally it is greenish and is marked with at least seven dark bars starting at the dorsal fin and which reach the belly.

The breeding males become chocolate brown in colour and develop bulb-like glands on the spines of the anal fin.

[7] The tompot blenny is found along the Atlantic coast of Europe from southern England and Ireland to Morocco.

[5] As most fish, tompot blennies harbour several species of parasites, including the capillariid Nematode Pseudocapillaria bainae.

Tompot blennies spawn in March to May the males mate with a number of females and guards their eggs.

When breeding the males develop pale cauliflower like glands on their anal fins which are believed to play a role in attracting females and in cleaning the eggs.

[7] The specific name was first used by Francis Willughby in 1688 after he had observed these blennies in Venice and heard them called gatto ruggine which he translated as "rusty cat" or "rust colour", although he was afraid that he did not fully understand the name.