Are there dogfish in Dublin Bay?

Kate McGonagle

At first you would probably say yes, right? There’s lesser-spotted dogfish and large-spotted dogfish all over Dublin Bay - but the scientific answer is a little bit more complicated. Scientifically speaking, these are both species of catfish, and the lesser-spotted dogfish is now more appropriately named the small-spotted catshark, and the large-spotted dogfish, or bull huss, named the nursehound. We’re not 100% sure why they are called dogfish, but this naming difference tells us more than you might think, as the change in name paints a very different picture on the evolutionary tree that these sharks have branched from.

“True” dogfish are in the family Squalidae, which includes sharks like spurdog, and are part of the superorder Squaliformes, which includes 126 species of sharks from a few different families. The spiny dogfish is probably the best example of a “True” Dogfish.

 Catsharks, on the other hand, are from the family Sciliorhinidae, in the superorder Galeomorphs. All living sharks are classified as either Squaliformes or Galeomorphs.

The Galeomorphs are older, branching off 273 million years ago, while the Squaliformes branched again 216 million years ago (Sorenson et al., 2014). Because of this, our local catshark species are actually more closely related to great whites than they are to true dogfish, which makes these common “nicknames” pretty confusing.

Most catsharks lay eggs, commonly called mermaid purses, and you can find these washed up on the shore and under the water. Mermaid purses have long tendrils at the ends, and a catshark will swim around and around what she is attaching her egg to in order to tie it down and stop it from drifting. Next time you’re out on a Dublin Bay dive, have a look around the kelp and the rocks, because you may be able to see the tiny catshark inside!