From the paper Reproduction of female spiny dogfish, Squalus acanthias, by Thomas S. Jones

The spiny dogfish  (Squalus acanthias) is a relatively small shark with a characteristic spine in front of each dorsal fin.  Its dorsal side is grayish and has sporadic white spots.

Although it may reach a length of 160 cm, most individuals in the North Sea are in the range of 80–100 cm (Ford,  1921).  It is distributed worldwide,  absent only from
tropical and polar regions.

The spiny dogfish has been harvested for more than 100 years mostly for its oil-rich liver.  At first, the oil was used for lamp fuel and as a lubricant in machines. The oil was later (during W.W.II) used as a source of vitamin A. Today the dogfish is valued as food in many countries.

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