Why Oily Fish Is Essential for Dogs Including small oily fish  in your dog’s diet provides a biologically appropriate  and highly beneficial source of omega-3 fatty acids , specifically EPA (Eicosapentaenoic Acid) & DHA (Docosahexaenoic Acid) . These essential nutrients cannot be synthesized by a dog’s body and must be obtained through diet. ✔️ EPA & DHA help: Brain health  – Supports cognitive function, learning ability, and neurological development. Eye health  – Maintains