Morphological and metabarcoding dietary analysis of the cunner wrasse (Tautogolabrus adspersus) revealed significant regional variation, with large overlap between its common prey species and biofouling animals living on salmonid sea cages.

The stomach-less cunner wrasse (Tautogolabrus adspersus) has been experimentally used as a biological control agent for salmon lice that infest Atlantic salmon (Salmo salar) and to remove biofouling inside sea cages. The cunner demonstrates a strong population structure, suggesting that its diet, and therefore its usefulness for biological control, could differ among its populations along 1086 km of eastern Canada, in response to the biogeography of its prey species. Gastrointestinal tract samples were collected across 14 locations throughout five distinct regions from Southern Nova Scotia to Eastern Newfoundland between 2018 and 2022.