|A pigmy, stunted shark.|
For some of you this might be familiar, but not me. I did asked the monger and he said it was a marble goby. But, judging by its cover, I just could not believe him. So, I dig it up.
The closest information I could get was that this is—correct me if I'm wrong—a spiny or smooth-hound dogfish, Squalus acanthias, one of the smallest shark species. Preferably known as cape shark in the United States market, rock salmon or huss in Great Britain (used in classic fish and chip), small salmon or saumonette (from its salmon-pink flesh when skinned and beheaded) in French, sea eel/zeepaling/seeaal in Belgium and Germany.
Yet, my most important finding is from Wikipedia. It said that their conservation status classified as vulnerable on the International Union for Conservation of Nature (IUCN) Red List. In the Northeast Atlantic their populations have decreased significantly, by at least 95%, over the past 15 years. It was also added into Greenpeace International list of fishes which with '...risks of being sourced from unsustainable fisheries', in 2010.
Substitutes: Shark, swordfish and monkfish in which have similar firm-textured flesh may be used as substitution.
GrowinKitchen's recipes using spiny dogfish:
Fish and Chips