How do short-horned sculpins and European miller’s thumbs reproduce?

Short-horned sculpins and European miller’s thumbs are both members of the Cottidae family, which generally follow the practice of being oviparous (egg-laying) and having the males guard the eggs until they hatch.1

Specifically, both the northern Atlantic short-horned sculpin (also known as the bullrout) and the freshwater European miller’s thumb are known to build rudimentary nests that are guarded by the male. Additionally, the males of these species possess a well-developed structure called a urogenital papilla, which some experts suggest may be used to introduce sperm into the female. Many cottoid species also exhibit pronounced breeding coloration, which is believed to assist in sex recognition and territorial behavior during the reproductive process.1