What is a "mud shark"?

"Mud shark" is another name for the spiny dogfish, a type of small shark notable for having a spine on each dorsal fin capable of injecting venom as a defense mechanism. The spiny dogfish is common in temperate waters around the world and is also used in cuisine.

Spiny dogfish are the most plentiful species of shark in the world, although the risk of overfishing is amplified due to the fish's slow maturation and long gestation period. Spiny dogfish are also used in the production of some fertilizers, liver oils and pet foods, and they are also a popular model for dissection in high schools and universities.