ORO - Northern Mermaid

https://www.liberdistri.com/en/artbooks/782-bjoern-hurri-oro-9782382890691.html
Book can be found here

Mermaids look quite different in the north than in other waters. Compared to their warm water kin, they have thicker skin to insulate them in the frigid depths and more rows of narrow gills to better filter the dark, murky waters.
They are also significantly more shy when humans are near, preferring to be far away where food is more plentiful.